vi | NewScientist | 7 July 2012
Markers on his body track every movement and can be analysed in great detail afterwards to
Gaming and sport are moving ever closer. Nintendos Wii console introduced a level of sporting activity into the home and uses accelerometers and gyroscopes to track the motion of the hand controller. The introduction of Microsofts Kinect in 2010, however, has taken video capture to a whole new level. The Kinect is a 3D depth-sensing camera it projects an infrared pattern of dots that bounce off an object or person and are picked up by an infrared camera. Complex algorithms convert the pattern into a depth field, while a standard video camera picks up colour images.
In effect, the Kinect does for less than $100 what complex motion-tracking systems do for a thousand times as much albeit at only 30 times per second and with less accuracy so far. Initial testing shows that, without much modification, Kinect can measure the volume of a typical human torso to within a few per cent and knee angles to within 10 degrees. The beauty of the Kinect is that it tracks hundreds of thousands of points in each picture, giving a complete 3D image of the body.
It is early days yet, but already prototype systems have appeared that can track the centre of mass of badminton players, or can simply gather measurements such as the players height and the length and width of their limbs. For now these systems are only available to those at the higher end of sport, but it will not be too long before Kinect-like derivatives are available in leisure centres or sports stores.
The implications of this are not hard to see. Before long there will be low-cost devices possibly on our phones with depth-sensing cameras to measure 3D motion in the field. This will solve the long-standing problem of tracking athletes cheaply in action, and without using any kind of marker. And it will be available to anyone, at any level, who just wants to perform a little bit better.
When attached to the body, sensors such as 3D accelerometers, gyroscopes and GPS can provide a wealth of information about an athletes position and orientation. Until recently they were so expensive that only university research departments and sports ruling bodies could afford them. But all that has changed. Todays
smartphones and gaming devices include such sensors, and this has driven down their price
so much that commercial athlete tracking systems are readily available. Indeed, many football, rugby, hockey and rowing teams are using the technology.
There are now even portable wireless systems that can measure heart activity
using electrocardiography, and muscle activity using electromyography. Air pressure and temperature measurements are there if athletes need them too. If it can be measured, it is being measured.
Just as the technology found in smartphones is helping elite athletes, now everyone with a smartphone can access the basics. There are already hundreds of sports apps for phones and many measure performance, mostly for outdoor pursuits. There are of course places where GPS doesnt work, such as a squash court or bowling alley, and other technologies that would be useful, such as integration with video. Here, the solutions are coming from the gaming industry
120707_IE_Sports engineer.indd 22 27/6/12 14:17:40
7 July 2012 | NewScientist | vii
Sport is an early adopter of technology and at the turn of the 21st century, better performances were characterised by new materials and cheaper manufacturing. The biggest change happens when a technology is introduced for example, carbon fibre led to radical redesigns of bikes, boots and boats. But after a while there are diminishing returns with each new design.
What will be the next big thing to prompt a step change in performance? Mobile devices such as phones, cameras and gaming consoles are one of the fastest expanding markets. They are likely to enhance sport with their ability to measure an athletes performance and analyse it. For the first time, we will be able to quantify and understand the effect of a piece of kit in action on the pitch or court. Buy a new tennis racket or set of football boots and they may have sensors in them that tell you not only how well you are playing, but how you can improve. Amassing data out in the field without interrupting play has long been the ultimate goal for sports engineers the humble cellphone might just do the trick.
THE FUTURE OF SPORTS ENGINEERING
Sports engineers develop new equipment and technology and then have to work out whether it actually makes a difference. One way is to give an athlete a new golf club, for example, or a pair of shoes and test them before and after to see what changes. The test usually involves measuring the position, speed, acceleration or force of both the athlete and their equipment.
For instance, divers jumping from a 10-metre platform are interested in the forces beneath their feet and how they translate into a high jump with more time to execute their complex twists and rotations. Runners tend to be obsessed with time and distance, so tracking their position is key. Archers must be stable when they release the arrow, so measuring how still they stay is important to them. Here are some of the techniques used, together with their pros and cons.
force, motion, speed
tracking technologies will soon be available to everyone who wants to perform a little bit better
The results are usually instantaneous and can be integrated with video or motion capture. But only ground reaction forces can be measured and it is difficult to make these measurements outside a lab. Again, the systems are relatively expensive.n Acceleration can be measured directly using body-mounted sensors. Accelerometers have shrunk in recent years with wireless devices becoming almost ubiquitous. However, speed and position are often more important to an athlete than force and acceleration. While it is possible to work out them out, it takes a trained eye to manipulate the data to avoid noise and errors creeping in.
So what would be the perfect system for sport? It would be cheap, but also able to measure position, speed, acceleration, physiology and be synchronised with 3D video. And ideally, markers or sensors would be unobtrusive or not necessary at all. Complex data analysis would be hidden from view and only the important pieces of information would be fed back, just as with TV replays.
n Motion tracking generally uses an array of digital speed cameras taking pictures at around 500 frames per second. For comparison, a standard camcorder takes 30 frames per second. Multiple cameras around a room can track reflective spherical markers attached to an athletes body at joints such as the knee and key points such as the hands. The same motion-capture system was used in movies such as The Lord of the Rings to track actors and turn them into realistic avatars.
The results can be impressive, with immediate video replay of the athletes skeleton in motion. The systems also give copious amounts of data for each marker. The flip side is the cost often as much as $100,000 per session, plus the need for special lights and a lab setting. Computers can only keep track of a limited number of markers, and when they are covered by the athletes movements, working out what is happening may take hours of tedious manual reconstruction.n Three-dimensional forces under the feet can be measured using sensitive plates sunk into the floor.
120707_IE_Sports engineer.indd 23 27/6/12 14:17:52
Instant Expert: The future of sports engineeringForce, motion, speediSportGame on