Do Force Platforms, Pressure Sensors And Smart Insoles Do The Same Thing?

Force platforms, pressure sensors and smart insoles are all devices that a person can step on and get some insight related to their weight or the pressure they are exerting on those devices with each step. Other than that, they are quite different and can have very different applications. This post is just an attempt to break that down. Feel free to jump to the different sections that are of interest:

[Force PlatformsPressure SensorsSmart InsolesSummaryMore on Smart Insoles]

Force platforms

A Force Platform (FP) is an equipment that you would typically find in a lab – an engineering lab, a biomechanics lab, gait analysis lab, ergonomics lab.. you get the idea. They are great for measuring forces applied directly onto its surface. So when a force platform is placed on the ground, you could step on it to find out how much force you are exerting on the platform. For those platforms that measure multiple axes, you could also slide an object across the platform to measure resistance forces between the surfaces. In sports engineering, FPs enable studies in walking/running gait, jumping (and landing), friction measurements in water polo balls or shoes or gloves, the coefficient of restitution of balls, aerodynamic drag (when placed in a wind tunnel), and more.

An example of a Kistler Force Platform (blue) set up in a wind tunnel

For anyone keen to explore what else is done with force platforms in sports engineering, feel free to do a quick search on these journals: Sports Engineering JournalSports Technology Journal or Journal of Sports Engineering & Technology.

Inside Force Platforms

The majority of Force Platforms in the market are set up with multiple Strain gauges or Piezoelectric sensors/elements that deform proportionally to the applied load. There is also the not so common Hall Effect sensing Force Platform which doesn’t require an external signal amplifier/conditioner like the strain gauges and piezoelectric sensors do. They are typically quite expensive and their prices vary with the number of sensors, size, construction, and additional data acquisition (or signal amplifier) systems.

For those who can’t afford the expensive systems and is adventurous enough to try and build something, a sports physics researcher from the University of Sydney wrote a paper providing details of a cheaper home made force plate. Essentially he used Piezos that were manufactured for sonar applications and they cost $25 each. A quick search on Instructables also showed one DIY instruction on making a strain gage force plate. For the slightly less adventurous, there is also the option of the Wii Balance Board as a cheap force plate alternative. There have been some validations of the gaming platform as a standing balance assessment tool, a golf swing analysis tool, and for use in other medical applications. The only downsides of the Wii Balance Board are the user weight limitation and that a custom software is required to access and read the data.

Pressure sensors

There are three main differences between Pressure sensors and Force platforms. Pressure sensors are typically flexible and can be placed on flat or curved surfaces, unlike Force platforms that have to be mounted rigidly. The other difference is pressure sensors do not measure force vectors. Thirdly (or a slight extension of the second), Pressure sensors only quantify pressure that is perpendicular to it (single axis) so it cannot determine shear forces or friction between two surfaces. Due to their flexibility, pressure sensors have been used to determine comfort and fit in aircraft seats for Paralympians, analyse medical mattresses, measure the pressure of grip during a golf swing, pressure distribution on bicycle handlebars, and more.

Single force sensitive resistor (FSR) from interlink electronics

Pressure sensors are mostly made out of either resistive sensors or capacitive sensors. The main differences between them are the sensing material used and their electrodes. They can be constructed as single sensing nodes or they can also be constructed in a row-column array fashion. The advantage of the array or matrix construction (over single nodes) is that it requires fewer connections. In an array, the intersection between each row and column is a sensing node. So a 3 by 3 array creates 9 sensing nodes while only needing 6 connections.  On the other hand, 9 single sensing nodes will need 9+1 connections where the +1 is the common ground. The difference becomes much bigger as the number of sensing nodes increases (For example 100 sensing nodes can be achieved using a 10 by 10 array that needs 20 connections or 100 single sensing nodes that need 101 connections).

Single Sensor Nodes Vs Arrays 2
A simple illustration of Single sensing node Vs Sensor Matrix/Array

However, the matrix construction is not without its challenges. The matrix sensor circuit is prone to parasitic crosstalk (capacitive or resistive). This means when pressure is applied on one node or multiple nodes, the electrical readings for other (unactivated) nodes might be affected. This is also known as “ghosting”. Unless some correction is applied, the measurements/readings become inaccurate and potentially useless. Also, the bigger the matrix, the more complex the correction. But if accurate absolute readings are not required, then it’s fine.

A related side story

I have been following the development of this smart yoga mat that was successfully crowdfunded on Indiegogo back in Dec 2014. Fast forward to 2017, they are still struggling to deliver the product. Looking through their updates, we can see they had to deal with sensor accuracy (possibly the crosstalk or ghosting issue); and on top that, some other issues they had include sensor durability, mat materials suitability, and accuracy of their tracking algorithms (which they are using some form of AI). Having prototyped a smart exercise mat around the same time they started, I can fully understand the challenges and why it is taking that long. Then again I am not sure it is worth all that effort. Personally, I think that simply relying on a pressure sensing mat to monitor and give (technique) feedback on yoga poses (or any exercises) has its limitations. Adding camera tracking (possibly utilising the camera on the tablet) might help. That saying, it is not stopping others from developing similar products as seen in this video.

Smart Insoles

Smart Insoles or Instrumented Insoles are essentially pressure sensors made in the shape of a shoe sole. The sensors are usually made in a similar fashion described earlier. Most of the Smart Insoles are also built with IMUs so that it adds a bit more context to the pressure data such as whether the wearers are standing, walking, running or jumping. The greatest advantage of Smart Insoles is they allow feet pressure mapping and measurement on-the-go. Things like continual gait analysis and activity monitoring, and it even has medical application likes foot ulcer prevention and falls prevention.


There are a couple of shoemakers that designed their shoes with the Smart Insole embedded within the shoe like the Altra IQ for running and the Iofit for tracking golf swing stance. The good thing about them is they have designed everything to fit properly into a shoe, made for a specific function. So users don’t run the risk of their Smart Insole not fitting properly into their shoes and collecting inaccurate measurements. On the other hand, users are restricted with specific shoes for pressure monitoring or activity analysis.  But at the end of the day, the pros and cons are really dependent on the individual.

Brief Summary

Going back to the question: “Do Force Platforms, Pressure Sensors and Smart Insoles do the same thing?”; there are some things that they are all capable of performing (e.g. gait analysis), but they all do it in a different way.  Also, there are certain measurements or monitoring that are unique for each sensor. Here’s a simple table that sums it up:

Sensors Measures shear force Measures Pressure Doesn’t require rigid mounting Portable Tracks Motion
Force Plates X X ✔/X
Pressure Sensors X ✔/X X
Smart Insoles X

More about Smart Insoles

Personally, I feel that Smart Insoles is a great idea, with many useful applications in sports and health. Over the last few years, there has been an increase in research and development in this area with many patents generated in the process; and companies around the world have come up with commercial products around the concept of Smart Insoles. It is definitely still in its early stages and I am not sure if it has even reached Early Adopters yet. Sadly, one company that I followed (Kinematix) has already closed shop due to a lack of funding. Perhaps it is ahead of its time like the adidas intelligent running shoe with intelligent active cushioning. Nevertheless, I believe the potential (of Smart Insoles) is there and I think targeting specific niches/problems will probably have a better outcome than designing for a generic application.

If you have an idea or project needing a smart insole or custom pressure sensor, feel free to contact us or leave a comment. We might be able to help you with it or at least point you in the right direction. As always, thanks for reading!

This post also appears on link.

Other related articles:

Accelerating Sports Technology Development And Innovation

Roughly 4 years ago, I wrote a post about crowdsourcing sports innovation – how sports companies and organisations were inviting people with ideas to step forward and pitch their innovations. Fast forward to 2017, the ways of generating new sports tech ideas have grown and evolved. From sports hackathons to accelerators, incubators, and Meetups, and online communities and invite-only/secret-squirrel investment funds or a mash-up of 2 or more of the above.  I am definitely no expert in this area but based on my very limited experience, here’s a look at a few of the possible ways to accelerate sports technology development and innovation.

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One way of defining hackathons* (from HackathonAustralia) is this: “Hackathons are competitions that challenge people to create something over a set time period using technologies.”. So in the case of a sports hackathon, that “something” created would be an innovative sports tech solution that meets an existing need/pain. It could be a hardware solution or a software solution or both.

[Themes] Depending who is organising or sponsoring the hackathon, events could have a specific theme/focus like the Western Bulldogs hackathon that provided participants with their athletes’ GPS data to do further analysis or the Future Of Sports Tech Hackathon by Enflux that allowed participants to use their motion capture technology or the Hack4Sports that had a focus on building sports tech startups.

[Needs Assessment] Whichever the theme, the participants would require some guidance/directions on real needs vs good-to-haves. That’s where industry experts and end-users (sports clinicians/analysts/coaches etc) who are at the event, can offer that perspective. This could be through talks or interactive workshops on specific areas such as improving performance or injury prevention or increasing participation etc.

[Forming teams] Following that, teams need to be formed to design the solutions. Some participants might have already formed teams prior to signing up to hackathons. But it is quite common for people to rock up by themselves. So hackathons might dedicate a session for team-forming. Typically people who have a passion in the same area would team up. Other than that, it is also helpful to have a good mix of hackers, hipsters and hustlers in the team.


Hustler, Hipster and Hacker

[Pitching Comp] Most hackathons involve a pitching competition which means the solution (created within that 1 or 2 days of hacking) has to be validated with real life users/customers and has a potential market fit. The team with the winning pitch usually wins something that can help them take their idea further. That could be prize money or often they get to be part of an accelerator program to develop that Lo-fi prototype into a minimum viable product (MVP). Else they at least have bragging rights.

[If you are interested in a sports hackathon, please complete this SURVEY]


Sports Tech Meetups (literally on the Meetup site) are to some extent scaled down versions of hackathons and/or pitching competitions. It is usually a local group of sports tech-minded people getting together once in a while to do stuff such as pitch nights or show-and-tell or have people already in the industry sharing their insights and experience. There are no fixed rules and format which makes it quite casual and there are no barriers to joining a meetup other than geography. All you need is an interest in sports technology.

[Here’s a couple of examples: Melbourne Sports Analytics Meetup, Seattle Sports Tech Meetup]

This makes Meetups a good platform for people who are new to sports tech to come explore the field, network and learn more.  It is also good for people who have developed a concept or MVP to come and get feedback from others (through pitch nights or show-and-tells). The next steps for these people could be to take part in a hackathon or join an accelerator program or incubator.


Online Communities

I believe this is quite plain and doesn’t require much explanation. There are quite a number of online platforms that allow people with an interest or a stake in sports technology to be a part of. From Google Groups to LinkedIn Groups to Facebook Pages. But what I observed (at least on LinkedIn Groups) is that there are very little open discussions within the groups/pages. In most cases, article posts get “Likes” or 1 or 2 Comments. Sometimes the posts are just companies trying to promote their products and services which often gets no “Reactions” whatsoever. So I am not sure if these groups are any good at promoting or even accelerating innovations in sports tech.

There is another online platform that has been growing in popularity (in the last few years) especially in the startup community – it is an invite only platform called Slack. Basically, it is meant to be an internal chat system for team members of an organisation to have work/project discussions. But one sports technology startup group that call themselves Starters decided to jump on this platform and allowed anyone who is in a sports tech startup (or trying to build one) to sign up to be part of the group. Though there is a fee to get in, it’s mostly to ensure that only people who are seriously interested join.

Screen Shot 2017-04-10 at 9.24.07 PM

But what is happening within this Starters Slack group is quite phenomenal. Ideas are exchanged, there are open discussions, Ask Me Anything (AMA) sessions, connections and introductions are made online, followed with meet-ups in real life, actual events (hackathons, accelerator programs & meetups) are organised and promoted, and I am sure there is more happening between individuals through direct messages (DMs). What’s amazing is that though it’s mainly based in the US, there are individuals and companies participating from all over the world.

Screen Shot 2017-04-10 at 6.14.18 PM
Starters – a global sports tech startup community

Slightly similar to Starters is a SportsBiz slack group started by the SportsGeek from Melbourne.The main difference is that there is slightly less emphasis on startups or sports technology and more on sports business in general. But the objective is not that different – to use the platform for sharing ideas, finding collaborators and opportunities, and ultimately pushing the sports industry forward.

Screen Shot 2017-04-10 at 9.40.01 PM

Some Key Points

So there are a few key points that I take out of this. One of it is, we need to collaborate. No one can build anything great on their own. Not only do we need a diverse team with different skill sets, we need input from other people (locally & globally) or run the risk of tunnel vision. Secondly, competition spurs innovation. Which is quite apt since we are talking about sports technology here, where one of the aims of it is to help athletes perform better and win the competition. Lastly, none of the avenues on its own can be the be-all, end-all of this topic. Especially if we are talking about building successful long-term sports tech enterprises. People at different stages of their ideas or development would probably go through a different process. What may work for some may not work for others. We may need to change from something that doesn’t work anymore (e.g. LinkedIn Groups) to something else that does (e.g. Slack).

I know I haven’t commented much about accelerators and incubators. That’s mainly because I have not had any personal experience with them. What I do know is that you need to at least have a team (and not just a great idea) to be part of an accelerator and preferably an MVP to join an incubator.

Finally, I think for someone who: has a few good ideas, is passionate about  (or has some exposure to) sports technology and doesn’t quite have a clear direction or built a team yet, a sports hackathon can be a good place to start. This is something I would like to explore a little more. So if you think the same way and would like to take part in a sports hackathon (or not), or if you have other thoughts on accelerating sports technology innovation, do help me out and complete this SURVEY or leave a comment or drop me a message on Twitter or LinkedIn. With that, thanks for reading!

This post can also be found here

*Hackathons have also been known as hack days, hackfests, startup weekends, makeathons, design-athons etc.

The challenges of making Smart Sports Garments

What is a Smart sports garment?

Smart sports garments or smart performance garments is a relatively new product segment in the consumer sports tech market. There are probably different views of what the definition should be, but for the purpose of this post, it is a sports garment with embedded sensors/electronics. The main functions of sports garments include providing covering, protection, comfort, ease of movement and some might say making the athlete more aesthetically pleasing. Then with the added sensors and electronics, there generally are two different types of secondary functions.

The more common one is the passive function where sensors monitor stuff on an athlete, either physiological measurements or physical movements. It can make smart evaluations based on the data and give real-time feedback suggesting to the athlete that they should push harder or rest or correct their technique etc. But the decision to act on that suggestion still lies with the athlete or coach. There is also the not-so-common active function where the garment does something to the user. For example giving electrical muscle stimulations (EMS) or possibly electric shocks. But so far the “electric shock” feature is only found on a wristband and hasn’t extended to any other wearables yet. I am not sure why that is the case. For EMS, it has been said that it helps with muscle strengthening which is good for rehab or as a complementary training tool. But I will not go into it since it’s beyond my area of expertise.

R&D in Melbourne

A while ago, I had the opportunity to be a lab rat for a mate’s PhD thesis. He has developed a patented novel technology to measure muscle activity and hopefully able to predict the risk of muscle and knee injuries in elite athletes. The experiment I took part in was basically collecting a bunch of data from this novel sensing technology, wireless electromyography (EMG) sensors, a motion capture system, and a bike trainer. Unfortunately, it also involved me pedalling for my life.

How is this relevant to smart garments? Well, the novel sensors and EMG sensors were all hidden under a compression garment with motion capture markers secured on the outside. The compression tights ensure that the sensors remain where they are (and reliably capture data) and they also (coincidentally) facilitate motion capture. Albeit it was a very crude way of combining the sensors and the 2XU tights, it was a functional prototype (of sorts), and the ultimate goal would be to have those novel sensors built into compression tights.

Lab rat in action

As we discussed further on commercialising this novel sensing technology for smart sports garments or developing smart compression garments with any wireless sensors, it became apparent that there are a number of challenges. Here’s just a few:

Washing and durability :: A sports garment is going to get sweaty and smelly a lot more than everyday garments. So it definitely needs to get washed. Most smart garments in the market have an electronics module (IMU, BLE module, battery etc) that is removable because they will not survive a tumble in the washing machine. However, there are still conductive pads or conductive yarns (for electrical connections). Would long term washing affect their conductivity and so usefulness?  (A research has shown that most conductive threads will be affected although some hold up better.)

Sensor data accuracy :: In order to capture accurate & robust data, the sensors have to be positioned in the correct location each and every time the smart garment is put on. For measuring stuff like heart rate or EMG, it needs to maintain skin contact for proper measurements. If sensor positions are off (by a bit too much) or skin contact is not maintained, the data collected becomes meaningless and cannot be compared with previous data sets. Not to mention the effect of sweat on EMG electrodes.

Custom fitting :: This relates closely to the above point. Most sports compression wear are made in standard sizes. Sometimes one might find their compression garment being a bit too long at the legs or too short for the arms or too tight around a joint and too loose at a certain spot. It’s fine on a regular compression garment. But when sensors come into play, especially when there is fabric type of sensors (that measures compression or stretch), perhaps a custom-fit garment could be a more optimal solution.

Application :: This is possibly the most important challenge – designing a smart sports garment that solves a real need. It could be a very niche area or a wide-spread problem. But the starting point would be talking to athletes, coaches and sports scientists, to identify where the need is or what needs to be tracked. Then the smart garment that is developed would be a solution and not just a cool piece of technology.

What’s in the marketplace

Having said that, over the last 4-5 years, more than a handful of companies have taken up these challenges and developed their own smart sports garments. A quick search on google shows that there are at least 5-6 smart sports garments in the market.

Brands / Companies
Measured parameters
Heart rate Breathing frequency EMG Motion 3D motion (joints)

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OmSignal and Hexoskin have smart garments that are an extension of heart rate monitors with an added IMU (Inertia measurement unit) which provides parameters such as breathing rhythm, running cadence, step count and more. While they both seem to be generic fitness trackers when they first came out, it looks like Omsignal has now dropped their original Omshirt and focused on a women-specific product (the Ombra) for running. This might have to do with a review like this: link.

       allsport_kit_600x680_01   1-ncipvwdjblutc7zvxalxaa

Myontec and Athos are smart compression garments with surface EMG sensors. The point of putting on these garments is for the user to know what’s going on with specific muscle groups during their run, cycle or gym workout. Myontec is focused on the lower body (quadriceps and hamstring) with an emphasis on running and biking, while Athos covers the whole body looking at general strength training. It is cool that their accompanying software/app provides feedback of which muscles should be activated more during a squat (or other exercises) but I think it might be better if they could correct a user’s posture/technique that is causing the wrong muscles to be activated.


Heddoko is a full body compression suit that measures a user’s 3D motion much like the Xsens suit. The difference is that the Heddoko suit uses less number of IMU and has embedded stretch sensors, which makes it unique. Assuming the measurements are accurate and repeatable, it has lots of potential applications in sports biomechanics and injury prevention. But based on this video, they are still validating their sensors and trying to work out specific applications.

Some additional thoughts

On one hand, it is cool that there is all these performance tracking technology available to the average athlete – such as wireless EMG and 3D motion analysis (again, assuming the measurements are robust). On the other hand, I wonder if the benefits would outweigh the costs because they are mostly quite expensive and I am not sure if the average gym goer would need that much information about their workout. Perhaps they would be more useful to elite or professional athletes, especially where professional teams have coaches and sports scientists to analyse the data, and give custom feedback. They could also couple it with video playback and analysis so that there is more context to the data.

I think for the average athlete, a smart garment might be useful if they are going through physical rehab and need to monitor certain movements or muscle groups while under the guidance of a physical therapist. Or if they are trying to pick up a specific skill like throwing a football or baseball (In fact, there are sensor embedded sleeves that do just that, which I might discuss another time). Basically, there should really be a specific ‘pain’ to solve. A smart garment with a generic health and fitness application is probably not going to be of much use. Wristbands and smart watches already try to do that.

Do you already own a smart sports garment or are thinking of getting one? If yes, do leave a comment. I would love to hear your thoughts and what you would use it for. Thanks for reading!

Tracking & Managing Anxiety in Athletes

The 2016 Rio Olympic games as with the previous games was a great platform for many tech companies to showcase their latest developments. There are radar and camera technologies that capture motion/biomechanics of an athlete on the field and in the pool. There are wearable devices that (also) track motion plus monitor physiological parameters 24/7. They aim to positively alter athlete behaviour and optimise performance. There are also sports apparel and equipment that were designed and developed (after much R&D) to enhance athlete performance. But we will leave that for another time.

Wearables for tracking performance

Going back to wearables and tracking systems; they often look at (somewhat) straightforward parameters – joint positions, speed (or velocity), height, acceleration, impact, angles, rotation rate, heart rate, heart rate variability, sleep and other physiological stuff. Sometimes coaches and athletes only need to look at a single parameter while other times they may need to examine a combination of variables and find correlations or visualise them over time to identify trends. Some companies go further by processing the above data and coming up with (trademarked) indexes such as Player-Load (Catapult), Windows of Trainability (Omegawave) and Recovery Score (Whoop). What they are trying to achieve is break down all the data that is being collected and deliver one metric that simplifies things and make it easy for coaches and athletes to measure performance (and recovery) .

In major games like the Olympics, where athletes trained years to prepare and qualify for that one event and possibly one moment, there can be a lot of anxiety and pressure to perform. Even if all the physical preparation has been done right, the results could still boil down to how well those emotions are managed; the difference could be between a podium finish or not performing as well as expected. So are there wearable technologies that monitor an athlete’s emotions and maybe warn the athlete of dangerous anxiety levels that can lead to choking or panic?

Wearables for tracking anxiety

Turns out there are a number of wearables in the market that do that. Here are three different types:

  1. Head-worn wearables that measure EEG signals (or brain activity) like the Emotive Insight and Muse. Although the Muse is designed as an aid for meditation and relaxation, it is basically monitoring four EEG channels to see how excited or relaxed a person’s brain is. The Emotive Insight has five EEG channels and looks at the user’s cognitive performance in areas such as Engagement, Focus, Interest, Relaxation, Stress, and Excitement. Emotive also has a higher spec neuroheadset that can look at fourteen EEG channels and goes into much more depth of what’s going on in a person’s mind and how he/she is feeling.
    Emotiv Epoc+: 14 channel wireless EEG system
  2. Wrist-worn devices that measure electrodermal activity (or EDA), blood volume pulse, skin temperature and motion; like the Feel and Empatica E4 wristbands. Based on research, measurements of EDA strongly reflect sympathetic activation which is linked to stress levels and excitement. Measuring heart rate variability through the blood volume pulse sensor also reflects sympathetic and parasympathetic activation. Skin temperature is another reliable measure of stress levels as shown in this research. Finally, motion tracking with inertial measurement units (or IMUs) helps identify the user’s activity and tries to place a connection between anxiety levels and what the user might be doing at that time.



    Screen Shot 2016-08-30 at 10.19.16 AM
    The Empatica E4 and Feel: 4 sensors packed on a wrist device



  3. Clipped-on devices that measure breathing frequency like the Spire. The Spire is built with force sensors; when it is secured onto the user’s waistband or bra, it detects the expansion/contraction of the user’s torso and diaphragm during breathing, thus deriving the breathing rate. Then algorithms are used to determine from the breathing waveforms whether the user is calm, tensed or focused.


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Spire: Breathing frequency tracker


Most of these devices also provide an accompanying app to monitor anxiety levels, and they prompt users to meditate or do breathing exercises. On a side note, a breathing exercise for lung patients was adapted for training athletes’ breathing technique and also focuses on dealing with anxiety. Athletes could also listen to music that either helps them relax or stay focused. In a way, managing stress levels on a day-to-day basis can be beneficial for athletes because stress levels can increase the likelihood of an athlete falling sick or getting injured, and it also affects recovery.

Emotion Profiling for Performance

On the other hand, when it comes to performing well during competitions/races, some athletes actually perform better with some amount of anxiety. In fact, different athletes in different sports may perform better at varying levels of anxiety. In other words, some athletes perform well at high levels of arousal while others may perform better at lower levels of anxiety. It’s all about finding a sweet spot. As mentioned in this article, one widely used tool by coaches/athletes to identify that sweet spot or optimal performance zone is the individual zones of optimal functioning (IZOF) model. This is a qualitative analysis approach that involves the athlete recounting the emotional experiences related to successful and/or poor performances. All the emotions are then labelled and rated as described here, and this creates an individualised emotion profile showing which emotions are helpful for performance and which ones are unhelpful. Of course, this would only work if athletes have competed for a number of times previously and came out with different outcomes (winning or losing or setting new personal bests).

Individualised emotion profiling (source: sportlyzer)

Ultimately we could utilise all the different wearables (and tools) mentioned above and somehow piece all that data together to shed some light on the inner workings of each individual athlete. Then the data could be used to “pivot” them in the optimal direction. But at the end of the day, its really down to the athletes themselves pushing hard every day and fighting battles with their body, mind and soul to get to where they would be. So let’s just salute the Olympic athletes for what they do and what they have achieved. And while we await the start of the Paralympics, I leave you with this video below by Under Armour and Michael Phelps. Thanks for reading!

Some thoughts and takeaways from #SAC16


The 2016 Asia-Pacific Sports Analytics Conference took place recently at the NAB Village. Its only the second time this conference is held and I have to say it has done really well. The numbers prove it – 865 attendees (according to the Whova app), 33 sessions that ran concurrently in 3 different rooms, 45 Speakers (all experts in their fields) representing 57 organisations, and 12 startups that pitched their innovative ideas/products/services.  There was even a waitlist 2 weeks before the event. This goes to show the growing booming popularity of data analytics, and the potential impact it could have on the different aspects of sports.

You know it’s a serious conference when it has its own coffee cup

Unfortunately, as with any great conference where there are sessions running at the same time, people would be torn between 2 (or possibly 3) presentations they are keen to attend. Fortunately, from what I heard, videos of all the sessions will be uploaded in a few weeks and we will be able to catch up with every single one that we missed. Just keep a lookout on the conference website here. In the meantime, here are some of my takeaways from the few sessions I managed to attend.

Smart equipment:

Professor Tino Fuss presented some of the research and development that was going on at RMIT including a smart cricket ball, a smart soccer boot and smart compression garment. With the advancement of inertia sensing microtechnology and novel pressure sensing technology, sensors can be placed unobtrusively on the athlete and equipment, measuring a range of parameters at much higher magnitudes. No doubt that the sensor data that’s acquired has to be analysed to solve a problem or confirm a hypothesis. That’s where analytics play an important role. But applying the appropriate sensor technology does open up opportunities to analyse new parameters like the sweet-spot on a soccer boot that increases the chance of a goal.

Wearable tech for rehab:

Shireen Mansoori is a doctor in physical therapy who applies wearable technology in her practice with elite athletes. She presented a model where she combined physiotherapy and data analytics for athlete optimisation. She uses Catapult units for monitoring an athlete’s Player Load & Hi Deceleration efforts to find trends that lead to injury. But she also uses other wearable tracking devices such as the Misfit shine on the athletes, health/wellness monitoring apps, and an athlete sleep screening questionnaire to monitor an athlete’s sleep and daily activities. Having other forms of data paints a much clearer picture of what an athlete is going through, and allows her to find out why the athlete is recovering faster or performing below expectations.

Video analysis & Artificial intelligence:

In cases where it is still obtrusive to place sensors on athletes (for example in swimming competitions); or where wearable sensors can’t provide specific activity/events information (for example attack, pass or steal events in hockey), sports analysts turn to video analysis/coding. However, much of the video analysis work involves a sports scientist (or two) manually tagging/coding every event during the competition. Stuart Morgan, sports analyst at AIS, talked about developing computer vision algorithms to  detect patterns and features and somehow automate the tagging. But this approach (human engineered method) has lots of limitations including it being non-transferrable and not very adaptable (for use in different sports). So AIS is collaborating with researchers at La Trobe Uni to apply deep learning (using Convolutional Neural Networks) to process the video images and work out whats happening. The advantage of deep learning is that it’s adaptable and it automatically creates new features. It still has some way to go as it’s not error free and users can’t really tell what logic led to the decisions.

Stuart Morgan talking about AI in sports analytics

From elite to grassroots:

Most of the stuff mentioned above happens in the professional/elite athlete space. However there is also an increased trend of sports tech/analytics companies developing products for athletes and coaches who participate in their local leagues. Hudl‘s video analysis software was first developed for professional teams. But today, their software caters to high school teams and their requirements. They have developed mobile apps that allows video recording and editing directly from the coaches’ mobile device, and there’s even a platform for sharing videos and facilitating talent identification.

Athlete tracking wearables have also moved in the same direction. Startup companies like Essential GPS and Sports Performance Tracking have developed more affordable tracking solutions so that teams with lower budgets can also track and monitor their players. Although it seems to be purely GPS data (without motion data), and only post game/training analysis (not real-time), it is still a good start. Or maybe a simplified, cost reduced system is all that is required?

From the startup community:

So there were 12 startups showcased in the conference. Other than the 2 mentioned above, there were 4 other startups that have built hardware in areas of performance tracking, drone racing, rehabilitation, and custom protective gear. The others were mainly software based, providing services and platforms in media, news, sales, marketing, VR and team management. They have all developed solutions hoping to fill a gap identified in the sports industry. Personally I am just amazed at some of the novelty and innovation they have come up with; and as this blog post says it, they are all innovators.

Bottom line:

I think what sums up this conference for me is that sports analytics is all about adapting and innovating. Everyone in their own ways are trying to fix a problem (or come up with a better solution) or improve work flow or even create new opportunities (e.g. esports and fantasy league). But the process is never a straight line from point A to B. The solutions need to be adapting over and over (almost like deep learning). Sometimes there needs to be collaborations and sometimes the end solution needs to be a combination of solutions. Whichever the case, iterate the process as quickly as possible till an optimum outcome is reached.

The”one-size-fits-all” solution doesn’t work very well anymore and mass customisation is becoming the norm. As mentioned by John Eren MP and Laura Anderson during their welcome addresses, we are slowly moving away from economies of scale and towards economies of scope.

Group photo after welcome address. From John Eren Mp’s facebook page (link)

Anyway, congrats again to PSCL and KPMG for another successful event and thanks for reading!

Dealing with the Heat

A while back, I wrote a post about overheating in the iPad – how too much heat renders the iPad useless because it just shuts down. When that happens, you could either remove the iPad from an external heat source (e.g. direct sunlight), allowing it to cool passively; or apply some form of active cooling to it (chemically, mechanically, or electronically). Then once the internal temperature has dropped below the “shut-down threshold”, the iPad usually performs normally again.

Athletes can also suffer from an ‘overheating’ type of situation and in some cases can lead to hyperthermia. Due to an extended period of high intensity physical exertion, and/or being in hot and humid conditions, an athlete’s core body temperature could go up to say 40 degrees C. Lots of studies have shown that this (excessive heat) can have a negative impact on the athletes’ exercise performance (or muscular endurance) and possibly some adverse effects on certain cognitive abilities.

So how do we deal with this heating issue that affects athletic performance? On top of ensuring proper hydration and sticking to safety guidelines (mostly common sense), there are a number of cooling strategies and technologies that could keep athletes cool, which then prevents heat illnesses, and ultimately helps maintain performance.

Heat Acclimatisation

Although not exactly a cooling strategy, heat acclimatisation is a common practice for athletes living in cooler climates and preparing to compete in warmer and humid climates. The acclimatisation process might involve moving to another location with similar weather to live and train, or it could be training in an indoor controlled environment where heating and humidifiers are applied. Basically, the aim is to get the athletes accustomed to the higher air temperatures and so reduce the impact of heat on their performance. In some cases, heat chambers are also designed to be hypoxic chambers so athletes can also be conditioned for high altitudes (which would be handy for events like the 2010 football World Cup).

An example of PAFC players training in a heat chamber in UniSA (source:

Cooling Strategies 

Pre-cooling is the process of cooling athletes before performing any exercise. There is evidence to show that pre-cooling procedures benefits athletes in endurance sports, and to some extent athletes in team-sports that require high-intensity repeated sprints (study link). It was gathered from this article that whole body pre-cooling is the more effective cooling procedure compared to only upper body cooling using cooling vests such as the adidas adipower or game ready vests. Although logistically, preparing the equipment for whole body cooling may take a bit more effort, compared to just distributing a bunch of cooling vests to the athletes.

An Example of a Portable Ice Bath from icoolsport

This article looked at a half-time cooling strategy that involves getting the soccer players to immerse their forearms and hands in 12 degrees water and putting a cold wet towel (that was previously soaked in 5 degrees water) around their neck. Their results showed that this primitive active cooling method significantly reduced the athletes’ body core temperature in 15 minutes.

A Novel Cooling Tech

A company called Avacore Technologies developed a novel technology that allows an athlete to cool down by simply wearing a specialised glove. How it works relies on the fact that the palm of our hands are radiator surfaces; which means when our body temperature goes up, blood flow naturally increases through those (radiator) skin regions to dissipate heat. This is achieved through special blood vessels called arteriovenous anastomoses or AVAs.

Retia Venosa

The glove system known as Rapid Thermal Exchange (RTX)  was invented by two Stanford biologists who were doing research on thermal-regulation. The system not only regulates a continuous flow of cool water through a pad (or grip/cone) which the user’s palm maintains contact with, it also creates a slight vacuum within the glove and that limits the blood vessels from constricting, which allows better blood flow and ultimately better cooling. There is a lot more explanation on their FAQ page, and links to scientific studies/evidence at the bottom of the page here. Or if you prefer to watch a video, check out this one from CNET where the presenter actually did a test herself and showed that it actually works – cooling her significantly and improving her endurance.

[A side note on the video: using an ingestible temperature sensor would have saved the presenter from that gagging experience (around 1:40 of the video)]

So not only is this glove technology keeping athletes cool and preventing diminished performance, coaches are seeing their athletes push harder and longer when the RTX is used in between training sets. The rates in gain is so dramatic that the gloves have been labelled as more effective than steroids. But even with such good reports, not everyone is rushing to purchase these gloves yet. As mentioned in their paper, the inventors recognised that there are a few barriers and one of it is people’s resistance to new views. Another challenge is to develop something more compact or even wearable, so that it increases the potential of effective application in other areas such as mining, firefighting, or emergency services.

Recently, Avacore launched an Indiegogo campaign to crowdfund their new consumer version which is just one standalone portable device instead of a few components. Looking at the number of backers, I would say it was very well received.

Different versions of the Avacore Cooling “Glove” (

Something for the makers and tinkers

Interestingly, someone who really liked the product but thought that the CoreControl Pro version was too expensive, decided to make a DIY version for a fraction of the price. He even made a CoreControl DIY Instructable. Based on the comments, there’s at least 2 other people who followed the instructions and built one for themselves. One other guy even made some improvements and published his own guide on how to build it.

Closer to home, a mate of mine also attempted to develop a product similar to Avacore’s hand cooling concept. One main difference is that his design does not require the use of ice and water, something that most of the methods mentioned earlier use. Instead, his entire system is electromechanical, very portable and can be easily switched between cooling or heating. If anyone in Melbourne would like to be one of the first few to trial his prototype, drop me a message/comment and I could help organise something.

Finally, with all the cooling technologies and methods out there for athletes, I think something that will really complement them, is a wearable temperature sensor (such as the cosinuss) that can constantly monitor body core temperature. That way, coaches can know exactly when to stop the athletes from their activity and stick their hand into a body cooling glove.



Versus Fitness: Developing A Smart Gym

with the combination of the sensors, smart algorithms and the gaming interface, this means: real-time tracking, with feedback of the users’ performance (score) or technique delivered right after each completed rep, and an overall quantified workout so users know how well they fare compared to their previous workouts

VersusOver a year ago, I wrote a post about developing with the Kinect and how I was working on a project that revolved around it. Fast forward to today, the project is now an officially launched gym that is also known as Versus Fitness.

What is Versus Fitness?

Versus is a system that has gamified fitness. By utilising different sensors and technologies, it is able to measure 3D motion, pressure, force, acceleration and power output of over 200 different gym exercises (and counting). With each proper repetition (or rep) that is executed, the user not only gets the rep counted by the system, a score is given based on the above measured parameters, and the score is scaled based on the user’s weight and height. In that way, 2 people of different weight and height doing the same workout can compete against each other on almost equal terms (Hence the name Versus). In case the term “wearable technology” comes to mind, no, there is nothing that the users need to wear to get their exercise tracked (maybe except a heart rate monitor, but that is purely optional). Just check out the video below.

How I got involved?

I started working on the Versus Fitness gym since late 2013 and it was purely by coincidence. Someone who knew Brad Bond (the founder of Versus Fitness) was at the RMIT Sports Engineering Lab on one of those Uni open days and he saw a novel sensor technology that would suit Versus. After a series of meetings and discussions, a research contract was set up to further develop that technology for Versus. This was partly funded by the Victorian Technology Development Voucher. At the same time, they were also looking for an additional team member to work on motion tracking algorithms. That’s where I came into the picture. Long story short I was offered a contract role on the Versus project which was partly funded by the Enterprise Connect – Researchers in Business grant (this has been replaced by the Entrepreneurs Infrastructure Programme). Kudos to Aaron Belbasis who was a key connector/initiator who brought everyone together and who was also one of the key researcher who helped develop the novel sensor tech. There’s a bit more details about the RMIT-Versus collaboration here.

What Tech are we talking about here?

One of the sensor technologies came from the research collaboration mentioned earlier. The team at RMIT calls it a “sensor-less sensing platform”. The closest thing would be Force Sensitive Resistors (FSR) like the ones from Tekscan. If you had a proper look at the video above, you will see the “sensor-less sensing platform” used in the floor exercises and some of the running exercises. Basically its a sensor that measures pressure.

There are other sensors that were developed or customised for tracking motion and a number of them are available off the shelf or at least purchasable online. In fact some of the sensors (like load cells and accelerometers) are similar ones typically used in the manufacturing, or automotive industry. A lot of custom fittings, enclosures and mechanisms were designed for the sensors before they could be installed in the gym. Majority of the design were done in-house and prototyped with the help of a MakerBot replicator.

But what really made the sensors (tracking system) worked effectively are the smart algorithms that processes all the sensor data and accurately identifies when each person is performing the exercise properly and evaluates how well he/she has done it. Initially when designing the algorithms for tracking each type of exercise, it all seemed pretty straightforward; but as things progressed, it turned out there were quite a few more considerations – e.g. filtering out “incorrect” movement data that resembled an actual rep, or profiling movement data from users of different abilities (or fitness level) etc.

Perception & Reality

Another important part of the system is the “gaming interface” or the “gaming control centre”. It is the personal trainer’s assistant. It relays to the users what exercises to do, records their performance, stores the performance data in a database, reminds the user how well they did previously (their Personal Best), manages the equipment (to some extent), and ensures that every exercise station is in sync so that the workout runs smoothly. That allows trainers to focus on one of the things they do best: scream at motivate people.

So with the combination of the sensors, smart algorithms and the gaming interface, this means: real-time tracking, with feedback of the users’ performance (score) or technique delivered right after each completed rep, and an overall quantified workout so users know how well they fare compared to their previous workouts (and with other users).

Future Developments?

The very first Versus Fitness gym is based in Moorabbin and that has seven different exercise stations (as seen in the video above). One could call that the full Versus experience. There are a number of possible developments in the pipeline. One is the development of new exercise stations to increase the type of exercises that can be tracked. Also, there are possible opportunities to customise the system for the elite or professional athletes, or even rehabilitation applications. Something that is definitely in the works is a “multi-station” concept – a single exercise station that has several sensor solutions allowing tracking of a few different types of exercises (e.g. dumbbell, kettlebell & floor exercises). This significantly reduces the footprint of the equipment and would suit small gym spaces. In fact this is currently on trial in a gym somewhere in Australia, and depending on how things go, you might start finding the VS logo in many more places!

A Look at Smart Balls

Tracking how fast a ball was kicked or thrown used to be done with an external device – it could be a speed radar or a high speed camera or maybe even a very trained (and experienced) eye. However in the last 5-6 years, more and more engineers and scientists have tried to put some form of sensors inside the balls to measure linear velocity, spin velocity, spin axis. This has mostly been made possible with advanced developments in microelectromechanical sensors (MEMS), where accuracy and measurement range have increased significantly (while still keeping the small form factor). Another 2 tech contributions that helped keep the sensors (more permanently) in the balls are wireless connectivity (Bluetooth or Wifi) with the micro-controllers and wireless charging.

Smart Ball Construction

Although the electronics is key to measuring movement signals and processing, there is still the very important task of holding those components (sensors + micro-controller + wireless modules + battery) inside the ball. Let’s call all those components the core. So while designing a method to secure the core within the ball, one has to consider the weight and position of the core and how it affects the centre of mass of the ball. The method has to be robust enough since the ball will take lots of impacts as it’s kicked or thrown or bounced. The method of securing the core will also affect or determine how the ball is constructed. Here’s a look at some of the different type of “smart” balls and their construction:

Smart Basketball: 94Fifty

Patent image – position of sensors

The way that the 9DOF sensor is built into the 94Fifty ball is rather unique (thus the patent). According to their patent application, there is an inner cavity on the surface of the inside of the ball, which is purposed for a casing to house the electronic components (core). The casing is built with flexible material such that the walls can flex with pressure difference between the inside of the bladder and the inside of the housing. The patent application also mentions providing access for battery charging but that was probably the early version. The new version is built with bluetooth connectivity and wireless charging.

The ball is constructed according to the official size and weight which is 29.5 inches (749.3mm) and 22 ounces (623.7g). So with the extra weight added from the core, the designers made adjustments to the enclosure material so that the overall weight is close to the standard weight, and more importantly the weight distribution is compensated so it spins like a standard ball. For example, if the core is positioned at the top of the ball (see image above), and the valve is placed 180 degrees from the core, extra weight would be added around the valve until balance is achieved.

Smart Soccer ball: adidas micoach

adidas miCoach Smartball

adidas’ smart ball is designed with it’s core positioned within the ball and held there by what looks like 12 sets of supports. The core is positioned or suspended right in the centre of the ball, and the supports are meant to be rigid so that the core is always in the dead centre. There doesn’t seem to be any patent related to the method of supporting the core but there was a patent with regards to the electrical wiring within the ball. The patent basically describes how wiring is arranged along the bladder wall to interconnect two electronic devices. It also mentions that the electronic components are arranged in such as way that the ball is balanced and doesn’t affect playing properties of the ball. According to the adidas page, the core consists of only a tri-axial accelerometer. There is also wireless charging with their custom induction-charging stand. The induction coils would likely be placed along the bladder wall instead of in the core.

Smart Cricket ball

The Sportzedge group at RMIT developed an instrumented cricket ball for measuring spin rate and calculating the position and movement of the spin axis (link to the conference paper). Due to the high spin rates of wrist spinners (up to 42 rps or 15,120 deg/s), typical off the shelf gyroscope sensors can’t manage that measurement range. What this smart cricket ball has are three high speed gyros that can measure +/- 20,000 deg/s, one for each axis. This ball is not built in the typical manufacturing process. In order to house the electronics, meet weight requirements, and keep it balanced, 2 solid halves of the ball was designed and CNC machined from the material Ureol or RenShape® BM 5460 which had the right density and hardness. Eight holes within the ball allowed for additional masses to be inserted to balance the ball. According to the paper, this design is an initial prototype and it is still not robust enough to be hit by a cricket bat. But it is fully capable for measuring spin rates during fast bowling. Subsequent versions will be more sturdy and also include wireless charging.

Instrumented cricket ball  (source: Fig 1 of the research paper)

Smart Oval Ball

The same team that built the smart cricket ball also developed a smart AFL ball to assess angular flight dynamics and precision of kick execution. The same electronics (high speed gyros) that were built into the smart cricket ball was also incorporated into this smart oval ball. The main difference is, this oval ball is made with two bladders that sandwich the core electronics, keeping them right in the middle of the ball. The bladders were inflated simultaneously to ensure a more even distribution of pressure.  It was noted in their paper that the advantage of using an inflatable bladder (instead of replacing it with expanded polystyrene beads) is that it allows for realistic kicking whereas the foam beads will absorb too much energy thus dampening the performance. Other than the smart AFL ball, a recent patent search found another American style football that is built with an electronic circuit coupled to an inflatable bladder. Interestingly, the football in this patent is designed intentionally with the electronics causing imbalance, unlike the above designs where the creators made sure their balls are balanced. Even though Wilson Sporting Goods has been granted this patent, there has yet to be any news of them releasing an instrumented oval ball. This might be something to look out for?

Instrumented AFL ball (source: Fig 2 of research paper)
Screen Shot 2015-02-22 at 9.57.14 pm
American Football – Wilson Sporting Goods

Ball Movement Measurements

No smart ball is complete if there are no “smarts” involved. The acceleration and/or angular velocity that is measured do not mean much if they are not processed and analysed. So firstly, the inertia sensors would require calibration – to ensure that the measurements are linear and accurate or at least corrected based on a benchmark device. Then mathematical models would be derived to determine the parameters for analysis; parameters such as spin rate, spin axis, speed, timing, ball flight path, angles, point of kick, bounces etc.

Also, to ensure that relevant data is processed accurately, certain “markers” or references are put in place to indicate when ball movement needs to be analysed and how it should be analysed. For the smart cricket and AFL ball developed by RMIT, as they are still in the research stage, a lot of the sensor measurements, signal processing, calculations and analysis are done manually. However for the commercial products like 94Fifty and the micoach smart ball, they have developed algorithms as well as guided user interface and instructions to make sure that each throw or bounce or kick is analysed accurately. In both cases, the interfaces and algorithms come in the form of an iPhone or iPad app. Here’s a breakdown of how each ball does it:

Screen Shot 2015-02-28 at 9.29.43 pm

Basically to analyse a kick with the adidas micoach ball, the micoach app needs to be turned on and connected to the ball via bluetooth. Then after the ball is positioned stationary on the ground, the user has to select his/her kicking foot and tap on the ‘Kick it’ screen before executing the kick. One condition for getting the parameters measured is to kick the ball at least a metre off the ground and for it to travel at least 10m. No bouncing or rolling kicks. 

Screen Shot 2015-02-28 at 7.16.33 pm
Proper kicks that will be tracked

Similarly the 94Fifty ball requires its app to be turned on and connected via bluetooth for the shots to be measured. For measuring shots, the user’s height needs to be entered into the app as well as the distance where the user is shooting from. There are options in the app to utilise a shooting machine or a user can practice with a training partner who can pass the ball after each shot. The only condition is that the pass has to be a chest pass for the subsequent shot to be recognised by the app. There are also some workouts or skill trainings that allow users to practice on their own and ball handling tracking options.

Screen Shot 2015-03-01 at 10.42.39 pm
Using the 94Fifty with a shooting machine

The Coaching Element

All these sensor laden balls and their accompanying apps with smart algorithms aims to help users become better players – whether it is improved technique in kicking or shooting or training of muscle memory to perform proper mechanics over and over.

The 94Fifty app provides real-time audio feedback for each shot that a user makes, whether the focus is on shot arc angle or shot speed or shot backspin. Based on ideal stats (e.g. arc angle of 52 deg and backspin of 180rpm), the user can fine tune his/her technique to achieve the right angle/speed/backspin. This user shows how by utilising the app’s feedback and capturing his practice on video at the same time, he could analyse his shot mechanics and identify how he could correct his shooting technique.

Likewise, the adidas micoach smart ball app not only measures each kick with ball speed, spin, spin angle, ball strike location & flight path, it also provides “Coach Notes” with recommendations on how the user can boost each specific parameter. A video option within the app allows a second person to capture the user’s kick using the iPhone/iPad’s camera so that the user not only gets the kick statistics but also visual playback of the kick.

Bottom Line

Designing a smart ball that analyses a player’s performance is definitely a complicated process. Not only must the instrumented ball behave like a normal standard ball with proper balance, the electronics incorporated within the ball have to be held robustly so that they don’t break under impact and the sensor data remains repeatable and reliable. Then there is the task of working out what parameters can be determined from the sensor data, if constraints/markers/references should be put in place to ensure accurate measurements, and how those parameters are helpful for improving an athlete’s skills and techniques.

Even with a properly designed ball that measures all the critical performance parameters accurately , it’s probably still not a complete coaching system. What the ball (and app) lacks is the ability to know (and break down) what exactly the athlete did in his kick or shot to achieve the numbers as calculated by the app. For example, in football, what affects a kick include: foot speed, which part of the foot kicked the ball, and the amount of upper-body movement; and in basketball, a few things that influence a free throw include: the amount of trunk and knee flexion, shoulder flexion and elbow extension. These range of movements could be tracked with either video analysis (such as Kinovea which is markerless) or a 3D motion tracking system (such as Vicon which requires markers), or wearable sensors (such as SabelSenseXSens or this new sensor embedded compression suit).

In a nutshell, smart balls are definitely great coaching tools. But if combined with athlete movement tracking, it would give a lot more insight to improving the athlete’s shot performance.

Of Racing Suits and Aerodynamics

Wind Tunnel tests with custom designed mannequins and different Under Armour speed skating suit prototypes.

In many sports that involve high speed movements, drag or air resistance is probably one of their biggest enemy in achieving their peak performance. One winter sport that faces this challenge is speed skating, and turns out altitude plays a big part as well – the higher the skating venue is, the less air resistance there is (more about that in this article). Also the effect of drag on the skater’s speed and performance is pretty significant and the suit that the skaters wear could have an impact on the colour of the medal they get.

So just before the 2014 Sochi Winter Olympics, there was a bit of news about the revolutionary speed skating suit designed and made by Under Armour and Lockheed Martin. The “Mach 39” was supposed to be the fastest speed skating suit ever made. Unfortunately, instead of delivering medals (gold ones for that matter), the result was the US athletes performed below expectations. Now, this could be due to the suit OR if we break it down, could be due to a thousand other reasons (on top of the suit)..

There was a bit of history to the design of the suit, and the basic idea was: just as dimples on golf balls reduced aerodynamic drag, adding dimples on the suit would have the same effect. Of course, other than the dimple design, there were other considerations like textile selection and compression fitting design. Just have a look at the video below that describes what the designers and researchers looked at to reduce friction and improve aerodynamics of the suit. What’s really interesting is how they customised the mannequins to typical skating positions for wind tunnel tests. (Drag to 4:00 of the video to just see the custom mannequins)

Although the rational behind the design and testing all seems to make sense, I can’t help but have a few questions:

a. With so much movements during speed skating, is it really possible to estimate the drag based on wind tunnel experiments? I mean, there are a number of sports that do drag tests in wind tunnels; like skiing and cycling. But these sports have moments of competing when the athlete maintains a certain position for a short period; and those are the moments where having an optimum position (aerodynamically) could really reduce drag significantly. But speed skaters hardly stay in one position during competition (maybe except at the starting line). Then if that’s the case, would the wind tunnel results be fully applicable on the track?

b. Friction plays 2 roles: it slows you down and it gives you more grip/control. If there is too much friction, it impedes movement; but if there is minimal or close to no friction, the athlete might lose control. How then, do we strike a balance between them?

c. Is it possible to measure drag dynamically on the track? Well, a company called Alphamantis seems to have done that, but with cycling, and in a velodrome fitted with gate sensors. Some additional input parameters they require include the bike’s wheel circumference and also inputs from standard power meters and speed/cadence sensors. With the power meters, there is a calibration process before the actual aerotesting where they apply a model to calculate drag. For more details of the testing, you can read ths interesting blogpost by DCrainmaker.

I reckon it is possible (in theory) to develop a model for speedskating (similar to what Alphamantis did for cycling) to estimate drag on the ice skating track. The model might be slightly similar to this one in wheelchair racing: when the speedskater is pushing off (and at equilibrium), there are 4 different forces applied on the speedskater: 1) Reaction force, 2) Inertia, 3) Friction between the ice and skates, and 4) Drag force.

  1. Reaction force (or applied force) can be measured by instrumenting the skates with a shoe sole pressure sensor similar to this or this.
  2. Inertia can be determined by measuring the forward acceleration of the skater (using an inertia sensor or a suit of sensors), then multiplying that by the overall mass of the skater.
  3. Friction can be calculate based on the coefficient of friction of ice which is different for straights and curves according to this paper.
  4. Finally, since the sum of all these forces equals to zero, we can determine the drag force!
Xsens Concept Tests in Speedskating

Of course this model is very much simplified and some assumptions are made, but if more thought is put into it, this might just work.

Anyway, going back to the lacklustre results of the Under Armour Mach 39 suit, there could be so many reasons why the athletes didn’t perform during those races. Since US speedskating has extended the contract with UA, they obviously know that the suit wasn’t the main culprit. It did sound like the athletes weren’t really used to the new suit, so maybe it’s just a matter of ‘breaking-in’ the suits.

Thanks for reading and if you have any thoughts or suggestions on aerodynamics or drag tests, do leave some comments!

(Also posted in

Developing with Kinect sensors for fitness and health

microsoft_kinect_sensorThe Kinect sensor has been widely used (hacked/developed/applied) by many ever since the Xbox 360 was first released. A couple of years ago, a fellow sports engineer from SHU studied the feasibility of using the Kinect sensor as a biomechanical analysis tool. He concluded that although the Kinect was fairly accurate, it wasn’t good enough for serious analysis (You can read more in his blog post here). The main advantage of the Kinect was (and still is) it’s price compared to professional motion sensors, and the Microsoft SDK which allows developers to come up with interesting applications (Check out various kinect hacks here).

I recently started working on a project that utilises the Kinect sensor. The project is basically developing a fitness product/system that combines the use of various sensors for assessing gym exercises. It is a rather interesting and novel concept because not only does the product quantify different gym workouts, it has a gamification portion where each user is competing with another gym user at the same time. No, it’s not like online gaming. In fact, this system is not designed to be used at home, but rather in a gym setting where participants perform the workouts together and get scored at the end of each session. Think Nike+ Kinect Training but for many people physically at the same place and with smart gym equipment (Equipment with sensors and smart algorithms). I probably should not go into too much details to avoid spoilers, but do look out for it’s launch sometime this year!

Nike+ Kinect Assessment
Nike+ Kinect Assessment

Anyway, I had the opportunity to test out the Nike+ Kinect Training (NKT) and found that it has quite a well designed interface that helps the user perform workouts with proper techniques. For example, the Kinect (ver 1) sensor is not the most accurate in measuring depth, so for exercises like push-ups, burpees, and core exercises like the bird-dog, the NKT gets users to turn to the side instead of face the TV/Kinect sensor; that way, the user’s movements are tracked more accurately. The concept of the NKT program is also pretty good because it starts with putting the user through an assessment – a series of movement tests and exercises, then rates the user in terms of strength, flexibility and stamina. Following that, it recommends a scheduled training program with a combination of exercises that can help you reach your goal (either to build power, become toned or lean). The feedback given by the on-screen personal trainer are usually quite spot on, usually correcting my posture, asking me to slow down (for exercises that are meant to be controlled) or speed up (for endurance type exercises), or just encouraging me to push on for the last few reps. There are instances where the Kinect sensor was unable to track some of my joints accurately and failed to count my reps, especially in a few of the floor exercises. But all in all, it is a pretty good program based on some sports science fundamentals and it could be an effective training tool for people who like to workout alone. I also got some good ideas off it that might be useful in the project I am working on.

{On a separate note, there has been some interesting devices/gadgets developed for the fitness and strength training folks in the last few months:

  • PUSH – a wearable arm band (possibly built with inertia sensors) that is able to determine force, velocity and power of each strength training rep
  • Hexoskin – another wearable smart apparel that not only measures movement (activity level, steps, cadence), but also the users physiology (heart rate and breathing rate).
  • Athos – similar to the Hexoskin, it is a wearable smart apparel with the addition of electromyography (EMG) capabilities embedded in the apparel.
  • Skulpt Aim – a mobile device that measures the user’s body fat percentage and muscle quality in individual muscles.

These devices (and other smart devices) could potentially become a common sight in gyms in the near future, allowing users to track more about their workout sessions and gain more understanding of what’s happening. A common trait among these gadgets is that they all have (or are developing) iPhone apps, which means users will have access to their workout history on their fingertips and probably be able to brag about it on social media.}

Going back to the Kinect sensor, apart from sports and fitness applications, developers have also come up with practical solutions for the medical and health industry. One such application is the Teki system developed by technology services company Accenture, and a few other partners including Microsoft. The main purpose of the Teki system is to reduce the need for elderly patients to travel to the hospital for routine consultations and check-ups, saving time and money. Using a Kinect sensor, set up at the elderly patient’s home, together with a few other wireless medical devices like a pulse oximeter and a spirometer, the doctor is able to do a remote consultation using a webcam in the hospital/clinic. The Kinect sensor comes in when the doctor needs to evaluate the patient’s range of motion; or when there are prescribed rehabilitative exercises that the patient need to perform and the Kinect sensor is able to assess and provide feedback to assist the patient.

Kinect v2
Kinect v2

It was mentioned earlier that the Kinect sensor isn’t the most precise in measuring movements, especially in terms of depth and also higher speed motions. Although the specification says that it could measure up to 30 fps, but after testing it myself, I found that it is usually around 15-16 fps (depending on your program). Lighting and certain background objects could also affect the detection of a full skeleton. But all these little ‘glitches’ will no longer be there with the release of the new Kinect 2 sensor which features improved performance over the original Kinect. Those improvements include: a wide-angle time-of-flight (ToF) camera allowing better range (or depth) measurements; capturing 1080p video, and ability to ‘see’ in the dark with its new active IR sensor; it can detect more joints on the body (5 more than the previous) with much higher accuracy, and it can track up to 6 skeletons at one time. Also, it is capable of measuring the users’ heart rate via a change in the user’s skin tone and even detecting mood from the user’s facial expression. {Just watch this video that basically demos all the improvements.}

With this newer Kinect sensor, it will be a lot more exciting for hackers/developers and who knows what interesting applications could be invented. But as of now, there is still no news of when Microsoft will officially release the windows version of Kinect 2 for developers; for those who are really keen, there is a preview program with limited spots that you can apply for here!

If you know any other Kinect applications in sports and health, feel free to comment below. Thanks for reading and here’s wishing everyone a happy new year!