Sensors Support Sports Scientists

31 July 2012

Interview with

Professor Guang-Zhong Yang, Imperial College London

Meera -   As well as biological improvements, many of today's sporting successes are down to advances to technology.  Professor Guang-Zhong Yang is directing the Esprit Project at Imperial College London where his team are developing a network of body sensors to track every move an athlete makes.  I caught up with him at Science Museum in London to find out more about how they work...

Guang-Zhong -   Traditionally for sports science, the performance measurement is done in the laboratory setting and this laboratory setting typically involve large equipment and big markers attached to the body.  For general sports science this is fine in terms of understanding how the body functions, but for elite athletes, you want something that is small and non-intrusive, to figure out ways of how to improve the consistency and also competitive advantage of the athletes.

Meera -   So there are two benefits; you're getting people out of the lab and into a real setting so you can actually see how they would perform, and you're also trying to be as unobtrusive as possible.

Guang-Zhong -   That's correct, yes.

Meera -   So we're in the Science Museum at the moment where you've just launched a temporary exhibition in their antenna section.  And we've got one of your sensors here just in front of us and it looks just like a hearing aid but a bright blue one.

Guang-Zhong -   That's right.  This particular sensor is called an ear-worn activity recognition sensor.  Now let me ask you.  If I want to detect a problem with your ankle or your knee, or the way how you walk or run, where would you position your sensor?

Meera -   I'm thinking around the ankle or the joints there, but this one won't go there.

Athletes turning the first bend of the 200 mGuang-Zhong -   That's right.  Yeah, so this sensor is put behind the ear and is exactly to measure that.  Think for a moment how our human body actually controls balance and motion.  Where are our sensors positioned?

Meera -   In the ear because essentially, that's where balance is controlled, isn't it?

Guang-Zhong -   That's right.  In the inner ear, you have semi-circular canals to control the balance and so on. And so, our design is very much a replication of bio-design.  It will use the sensor put behind the ear and monitor your gait - which is how you walk or how you run; and also other motion factors or indices.  So if you have a problem with your ankle or your knee, you actually would try to compensate for that and to alleviate the pain, and therefore this changes your gait.  And you use this to be able to pick up these signs.

Meera -   If I had this ear sensor on right now and I'm walking along just in a straight line, what can you monitor about me in this moment?

Guang-Zhong -   So this will measure what we call ground reaction force.  So when you walk, you have the heel strike, then you transfer the body weight, then you have the toe-off and then you swing, and so on.  And with this, you can actually see this wave form in two peaks as you see here.  Typically, if you have to measure this in the laboratory, you either use a pressure insole, i.e. a sensor put in your shoes, or you use force plates which tend to be expensive.  And the advantage here is that you can do this in the free-living environment.

Meera -   Is it mainly this kind of movement, so things like gait, or are there other factors being monitored too?

Guang-Zhong -   It can also be used for monitoring your body trunk motion.  So the general posture.  Of course then when you add more sensors onto your body, you can actually recreate all your arm movements and also all the detail postures, almost like what you do for animation.  The thing here is that you can see the evolution of those sensors that we have made over the last 3, 4 years.  It did really has shrunk by 500 times.  You see the little sensor towards the right which is the size of your small finger nail.

Meera -   Yes, just less than a centimetre squared.

Guang-Zhong -   That's right.  It will measure all those things.  It's got wireless transmission and also, it has on-board processing and also can interface with other sensors as well.

Meera -   How does the sensor work?  It's on my ear and it's got this chip inside, monitoring so many things, but how does it monitor all of this?

Guang-Zhong -   This one that has got a very simple sensor, a 3-axis accelerometer.  So, it's a sensor that will measure both your static and also dynamic inertia; your orientation with regard to the gravity when you're static.  Also, when you're moving, you may have acceleration.  It will simply impose that with the gravity.  So, it's a combination of both, what we called the static and also dynamic inertia.  With this, then you can induce motion formation say for instance.  If you integrate that, it will give you the velocity information and if you dare to integrate again, it would give you the position and so on.

Meera -   I imagine that this is particularly useful for sports where people are moving just their body, and things like gait and speed perhaps are important, so runners?

Guang-Zhong -   For runners, absolutely, also for others as well - cycling, and other sports, rowing and so on.  It has many applications.

Guang-Zhong -   But as well as the ear sensor, you are developing a sensor network.  So, next to this one, there is a really clear patch with a distinct chip in the middle of it.

Guang-Zhong -   That's right.  This particular sensor is to measure biochemical information.  In this case, the lactate from the sweat as a surrogate marker to look at muscle exertion and so on.

Meera -   So lactate is something that people produce I guess as they do a lot of exercise and this is a way to monitor how much they're producing.

Guang-Zhong -   That's right.  You see the by-product it generates.

Meera -   Is sweat quite a good, accurate kind of summary of how much lactate someone makes?

Guang-Zhong -   In true fact, it's not, because sweat can be contaminated by a lot of other things in terms of biochemical content, the pH, lactate and so on.  But this is a very convenient way of getting the biochemical information.  Of course, drawing blood is not something that you want to do for athletes regularly.

Meera -   Will there be eventually a variety of sensors?  It's mentioned that the Esprit project will be looking at a range of sports and a range of types of factors in sports, so as well as someone's speed or gait, things like wheelchair motion or rugby collisions?

Guang-Zhong -   Absolutely.  We have developed a very small sensor that can be used for tracking a wheelchair:  Clip it on to the axle, look at the training power output, and also its position in the court.  And all this information is very helpful in terms of looking at the force exertion as well as, potentially, the tactics by the athletes.  You can integrate the sensor as a patch to be worn on the body or into the garment, or into a helmet.

Meera -   With these sensors, have they been trialled on any athletes and have you seen the way that they can benefit training?

Guang-Zhong -   Yeah, we are using this for a range of training exercise and things.  Really, the benefit is that you get the real-time information and also, you get quantitative information.  The sensors itself would not be able to make a medallist because it is really the work of the athletes, the coaches, and all the support team.  What we are contributing here is really one small facet of the entire training regime to help to maintain the competitive advantage.

Meera -   Professor Guang-Zhong Yang from Imperial College London.

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