Developing IMU Sensors For Capturing Motion In Sports

IMU sensors are pretty useful because when strapped to the right location and given the right context they can provide very insightful information about an athlete’s (or anyone’s) movements. In this post, we are going to look at a couple of options in the market that allows us to skip the hardware development and jump right into the application development. Feel free to skip to the different sections that interest you:

[ Intro To IMUsmbientlabsNotch SensorNotch Mocap TestCustom Sensors]

Intro To IMUs

In case this is the first time you are hearing about IMU, here’s a brief intro. IMU stands for Inertial Measurement Unit; it is an electronic device that typically has accelerometers, gyroscopes and magnetometers, and it measures its own acceleration, angular rate (or spin rate) and surrounding magnetic field. IMUs are not only used in sports, in fact, it is used in many consumer electronic devices. Our smartphones for one has IMUs for detecting the orientation of the phone and changing the display to portrait or landscape. The IMUs also allows for functions such as undoing texting errors, a spirit level and motion sensor games. If a user carries the phone with them in their pockets most of their waking hours, it can act as a pedometer counting steps and detect when the user is sedentary. For runners who use running apps to track their runs, IMUs enable some apps to track indoor runs and cadence. Sports Engineering Researchers have used smartphones for tracking wheelchair rugby activities and classifying different sporting activities.

As great as the smartphones are with inbuilt IMU, GPS and processing power to give us real-time analysis, we don’t really want to strap an expensive smartphone onto a football player’s calf to monitor their kicking or tape an iPhone to a tennis racket to measure swing metrics. That’s why companies like Qlipp has developed sensors for tennis or Zepp which has sensors for a number of bat-and-ball or swing type sports. Then there are sensors for rowing, running, surfing, mountain biking and more. There are also different sports equipment that has in-built IMU sensors. Like smart balls (basketball, football, cricket ball etc), smart shoes, smart helmets, smart rackets etc, it could go on and on.

But sometimes we might still not find a sensor product on the market that is right for our sports or health application. So we explore the option of developing something on our own. Fortunately, we don’t necessarily have to start from scratch* because these days there are generic IMU sensor platforms that are designed and built for people who want to develop a sensor for a custom application. They often have the standard 9-DOF (degree of freedom) sensor setup and come with software SDK that allows developers to build their own applications for processing and analysing the data. Let’s look at a couple of options below.

[*when I say scratch, I mean getting sensor boards from SparkFun, Adafruit, Seeedstudio, Tindie etc]

mbientlab

mbientlab successfully launched their first Bluetooth IMU sensor on Kickstarter. They pitched it as a development and production platform for wearables with simple API for iOS and Android. There was some simple soldering required when people bought the first product. I didn’t get one from that campaign but I did get a later updated version which they called MetawearRG. What impressed me when I first got it was the size of it – it’s small and compact and I could use it to build/redesign a smart basketball prototype for a client. Then when I started testing it, I found that their API was really easy to use and I could use their sample iOS app to build a custom app for testing within a (reasonably) short time.

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Smart Basketball Prototype and Watch app for tracking optimal shots

Since then, they have made many other versions of sensors with:

  • slightly different sensor configurations,
  • options of coin cell or rechargeable lithium battery,
  • accessories such as cases, clips or wristbands,
  • sensor fusion firmware,
  • cloud services, and
  • hubs to manage multiple sensors.
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Metawear RG with custom 3d printed sleeve/case (L) and Metamotion (R)

I haven’t had the chance to try everything but I have to say, I have had a good experience using their Metawear and Metamotion sensors to build various proof of concepts and I am still using them for a number of projects. The sensor data can be streamed to your smartphone or logged on the device. In terms of API support, on top of iOS and Android, they have added Python, C, C# and Javascript, so developers can build stuff on various platforms.

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Sample/Template Metawear iOS app for testing

Looking at their new website revamp and some recent emails they sent out about new platform developments, they seem to be putting more focus into the allied health space, in particular, measuring range-of-motion (ROM). They are currently beta testing an app called the MetaClinic and it looks like they are using skeleton-tracking the likes of motion capture systems which would probably mean we need to use multiple sensors. That should be interesting.

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MetaClinic App by mbientlab

Notch Sensors

Notch also launched on kickstarter, in fact slightly earlier than mbientlabs’ campaign. They had an interesting concept of integrating individual IMUs into custom designed clothing using pockets in discreet locations. Unfortunately, they weren’t successful at that instance. Their initial use case probably wasn’t strong enough. So I guess the founders went back to the drawing board, revamped it all and went with the “motion capture” approach for developers.

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Notch sensor with elastic band and clip

With the new design, the shape of the IMU sensor is essentially the same but they have ditched the micro-usb in each IMU for contact pins and made it water-resistant (IP67). They also designed elastic bands of varying lengths with a sensor clip and a user can secure each sensor up to 15 different locations on their body including head, chest, upper arms, wrists, hands, waist, thighs, ankles and feet. So instead of selling individual IMUs, they sell a kit of 6 IMUs with a set of elastic bands, and if a user wants to do a full (body) setup, they will need 3 kits.

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The Pioneer Kit: 6 IMUs with charging case and elastic bands with clips.

A quick test and review (for biomechanics)

I had the opportunity to run a short pilot test with one (the pioneer) kit in a biomechanics lab. I used the lower body setup which used all 6 IMUs strapped on my chest, waist, thighs and shins/ankles. In terms of setting up, it was pretty straightforward. After following an initial calibration procedure of all the IMUs in the case, I put on the bands and clipped each IMU to the right location according to the different colours as indicated on the app. The only thing is putting on the bands takes a bit of practice and I had to swing around to check that the bands are not too tight and restricting movement. Even though I don’t have muscly quads, I felt that the bands were somewhat tight and needed adjusting after a while.

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Setting up the Notch IMUs for lower body measurements

For testing, I did a simple protocol of walking, stopping and doing 3 squats of varying depths. Then I compared my knee angles measured on the notch and the motion capture system. A few quick things that I took out of the knee angle measurements were:

  • The angle measured by Notch is the exterior angle while the motion capture system looks at the interior angle. So it needs a quick recalculation before comparison.
  • Assuming the motion capture system is the more accurate measurement, Notch had a larger error as squats went deeper.
  • But for walking, the knee angles measured were quite close.

It’s wasn’t a very elaborate test but even from this simple outcome, I can safely say it’s probably not the best tool for accurate joint angle measurements. Although for a quick 3D visual feedback on movements, it might work. Here’s the clip of me doing the test described above (feel free to rotate the video to get different perspectives):



Further to that, I could only download angle data. If I wanted the raw sensor (acceleration and gyro) data, I would need to pay for an extended license that is renewed annually.

In terms of custom development support, they used to have support for iOS but they seem to have taken that off now and only have support for Android which I thought is a bummer. I am guessing they have some issues with getting it right on iOS. Hopefully, it is just temporal and they will resolve it soon. For Android developers, it looks like they have pretty good support and even provides a template app. I have to add that there is a fair bit of fine print I need to agree to before I can get access to their SDK. If I read it right, they basically want a licensing fee for using/commercialising their SDK.

Custom Sensors

Both of the above IMU sensors have similar specifications when it comes to measuring acceleration (using accelerometers) and angular velocity (using gyroscopes). The typical measurement range for accelerometers is +/-16g (that’s 16 times of gravitational acceleration), and for gyroscopes, it’s +/- 2000 degrees per sec. For many applications, this configuration is fine. But there might be some cases where higher acceleration needs to be measured and that goes beyond 16g, like shocks or high impact collisions. Or I might need high-speed rotations to be tracked and 2000 degrees per sec is too low, like measuring the spin of a cricket ball or gridiron football (which can come close to 3600 degrees per sec or 600rpm as demonstrated here by Drew Brees).

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Spin rates of a gridiron football during a throw test

As briefly mentioned earlier, hobby electronics stores like SparkFun, Adafruit, or Tindie would be a good place to start when looking for accelerometers and gyroscopes of different specifications. There are also lots of microcontrollers with Bluetooth Low Energy (BLE)  built-in that are Arduino compatible so we can program them with the Arduino software. One that I found pretty handy is this one called Blueduino which comes with a Lipo charger add-on (and add-ons are great) and that can be found on Tindie.

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The gridiron football sensor prototype using the Blueduino

Final Word

For those who are in research and possibly need Matlab and software support for building custom Matlab programs, definitely check out Sabel Sense sensors (Australia). Else, I reckon the mbientlab sensors would be a great option for starting a custom development. If I get a chance to trial their Metaclinic platform, I will put up another post. Meanwhile, do drop me a message here if you need assistance or advice in any of the options above and feel free to leave a comment if you know of better/different solutions out there. With that, thanks for reading!

The Kayak Tech Survey Outcome

Almost 6 months ago, I wrote a short post about (what I thought was) a lack of technologies for monitoring training in flatwater or sprint kayaking. To make sure that it wasn’t just me thinking that way, I created a survey and sent it to a couple of kayaking friends who graciously helped spread the word. I also posted a link to the survey on social media (i.e. Twitter) which I think wasn’t quite as effective. Overall, I didn’t get a big response but it still gave me a peek into things. So let’s dive into it and see what it’s telling us.

Key Stats

So here are some key stats as captured by Typeform:

There were a total of 120 visits, of which 101 were unique and out of the 101, there were 37 responses. This means a 36.6% response rate. Among the 37 responses, 14 were done on Laptops, 23 on Smartphones, and none on Tablets.

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Screenshot of Typeform Key stats

Some Details

Then onto the 6 questions:

  • Training frequency per week – 30 out of the 37 responses said they train at least 2 times a week or more.
  • Yes/No to use of technology during training – 30 out of 37 use some form of technology to track their training
  • Regarding the type of technologies they use – 29 use a GPS watch, 19 use a heart rate strap, 8 use a smartphone app, 3 use Motionize, 3 use Vaaka Cadence, 2 use a SmartWatch, and 1 uses a GPS + IMU unit. (note that some people use more than 1 piece of technology)
  • The number who do not use technology – 5 responded that they do not use any technology and the most popular reason is that they have not tried them
  • What they liked about their current technologies – Being able to track Heart Rate (n=18) is the top thing that people liked.  This is followed by Pace (14), Speed (11), Distance (8) and Stroke Rate (4) (or cadence).
  • Regarding improvements they would like to see, everyone had slightly different preferences. But in essence, 9 said they would like a kayaking specific device or app, 6 wanted stroke rate available in their existing devices, 6 wants some form of power monitoring (that is affordable), 4 would like to see stroke/technique analysis, 3 wants greater accuracy and reliability in their tracking, and 2 would like a better visual of their data.

[If you would like to see it on Typeform, here’s an overview of responses to the first 4 questions: link]

Even though I only had 37 responses, there was a good mix of opinions; and I take away 3 key things out of the above data:

  1. The GPS watch is the most commonly used tech. It makes sense because it is a multi-functional device – it can be used for running, riding, swimming or just for everyday use as a watch.
  2. More than half (19) of the people use a heart rate strap and it seems most of them value the heart rate data.
  3. Although there are technologies out there that can be used/adapted, 23 out of the 30 still wants some form of improvement to their devices. The most common feedback is there isn’t a kayak specific device or app.

I reckon most people would have a similar setup as the athlete in his Instagram image below – wearing a heart rate strap and with a GPS watch mounted onto the kayak in front of the cockpit.

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Tom Liebscher’s Instagram photo (link to original  photo)

Additional Info

Also from the few conversations I had with some of the kind people who did the survey, most (if not all) GPS watches don’t track stroke rate, and the accuracy of the speed measurement during short distances/sprints/intervals are not very good.

What I didn’t get a lot of information or feedback about are those kayak specific technologies that are actually in the market like Vaaka Cadence, Motionize and Kayak Power Meter. It seems like not many people have used them. This could be because of the price or a lack of opportunity to try it.  I will be digging a little bit deeper into that.

What next

The main outcome I took out of this little exercise is that my initial hypothesis has its merits, and it’s worth pursuing this further. The few options that I am exploring further going forward are (in that order):

  • Smartphone app (likely iOS)
  • A kayak specific device like a kayak computer
  • Garmin Connect app

As this is really just a side project here at ReEngineering Labs, the progress might not be as quick. Nevertheless, it will be moving forward and I will be posting updates every 3 months.

If you are reading this for the first time, please do check out the earlier post here, and have a go at the survey here. If you would like to give your input on kayak technologies or even be part of this project, drop me a message here. To get notifications about this project, simply subscribe on the right.

With that, thanks for reading!

 

 

How Technology Helps Measure Soccer Statistics and Tactics

Over the last 5-6 months, I have had different conversations with people who are working on technologies related to soccer. And I recall writing about Tactical Analysis in Soccer for SportTechie some years back and thought I will reshare it here plus add a bit of update as some things have changed since then.

What are some of the Football Tactical Analysis Websites?

Squawka is a tactical analysis web application that provides a platform where one can view real-time and post-match statistics of (almost) everything that goes on in a football match. This includes time of possession, number of passes, number of shots, shot accuracy, chances created, tackles (or duels), blocks (or defensive actions), player stats etc. Match analysis data is presented in a field diagram with coloured dots and lines and heat maps. Those statistics can then be filtered by team and player for various types of analysis – whether it’s comparing player performance or looking at shots from one team or overall team events. A useful feature is the timeline scrolling which allows one to look at specific 5 min blocks of match activity.

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Player Performance Comparison

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Shots – where they were taken and where they landed

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Events Heat Maps

The comparison matrix is another interesting tool on the site that looks at stats over an entire season. For example, one can select five different teams in the 2013/2014 season of the Australian League and compare stats that they are interested in. The stats displayed can be filtered by ‘total for the season’, ‘average per game’ or ‘per 90 metrics’. One can also compare teams from different leagues and different seasons.  

A special metric of this website is the Squawka Player Performance Score which is calculated using a large amount of data. This player performance score is broken down into “attack”, “defence” and “possession” statistics.

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Comparison Matrix Example

Four Four Two also provides match analysis data on their website in their Stats Zone section. It pretty much provides the same data available in Squawka, except the information is presented in a slightly different way and they don’t have a player performance score. The  Stats Zone allows all the match activities of a player to be viewed together in the Overall-player dashboard, instead of having to select the individual events in the Squawka dashboard. {Update: unfortunately FourFourTwo has discontinued Stats Zone due to limited resources}

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Stats Zone and what their Summary Statistics used to look like

Another site called Outside of the Boot writes commentaries and analysis on selected matches and supports their analysis using statistical data from the above two websites. Other than breaking down the statistics and what was going on in each match, they give reviews on the general style and tactics of a team, player or coach.

Where and how are the data collected?

Regardless of how the data is presented, what’s important is the reliability of the data and where their source is. Interestingly, both sites get their data from Opta, a sports data company that collect, package, analyse and distribute live data. Opta briefly explains on their website that their data collection process is labour intensive with three performance analysts assigned to each match; with one collecting all of the home team actions, one doing the away team and a third analyst checking the data for consistency and adding additional layers of data. They then run a full post-match check within 48 hours to ensure that the database is as accurate as possible.

But what exactly does each analyst do? By using their proprietary software, each Opta analyst puts in the live video feed of a match, then by using hotkeys, every activity that involves the ball is “tagged” – this “tagging” or tracking will record the time each activity started and ended and the X-Y coordinates of the start and end positions. For those who have used video analysis software like SportsCode (now owned by Hudl) or Dartfish, this will sound familiar. But what Opta has done is standardize their activity definition and tracking methods, so every analyst is trained to tag or code the exact same way. This means consistency in the data, allowing every match and every player to be compared using the same standards. The cool thing is, by feeding in historical matches (like all the past world cup matches), they can compare the performance of players from different decades. Check out this video that talks a bit more about what Opta Sports do:

Are there alternative (automated) technologies?

There are a number of athlete tracking technology out there that are either based on wearable technology (Catapult Sports, Tracktics, Polar Team, STATSports & SPT etc) or camera and image processing technology (Stats SportVU and TRACAB). The advantage of wearable sensors is that they can accurately track each athlete’s acceleration and impacts (in three axes) and some even track the players’ heart rate – something that is not possible with any of the current camera or video technology. But data from wearable sensors typically belong to the teams and not shared unless there is an arrangement with broadcasters. With Stats, they claim to not only track real-time 2D (X-Y) positioning data of the ball and the players, but its complex algorithms can also analyse and work out information like speeds, distances, possessions, passings, defence stats and turnovers. So technically, automating tactical analysis to some extent is possible but how much information can be made publicly available is another question.

Some final thoughts

The technology and methods used in Tactical Analysis in football have become more widespread over the years (and its still growing). The statistics that are made available can not only give punters additional information for betting, it can add new dimensions to watching each game. It provides viewers with a better understanding of what the players are actually doing (individually and as a team) and how they have been performing over a season with an unbiased quantified evaluation. For coaches and team managers, it means their decisions (in terms of training, strategising or even talent identification) don’t have to rely too much on gut feel but can be supported with numbers. How much they want to trust those numbers is another thing altogether.

If you know an exceptional app or technology in tactical analysis that is not mentioned here or maybe its still in development, feel free to leave a comment about it, and finally, thanks for reading!


Here are a few other related articles and blogs for those who like geek out a bit more on the topic:

  • Different Game: https://differentgame.wordpress.com/
  • Paper on big data and tactical analysis in elite soccer: link
  • Paper on tactical analysis using pattern recognition: link
  • Paper on a new tactical metric that looks at effective play: link

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.

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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.

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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.

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Source: Footlogger.com

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 sportstechnologyblog.com: link.


Other related articles:

Tracking & Managing Anxiety in Athletes Using Wearables

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.

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    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.

     

     

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    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 brain.fm 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).

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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!