When you open your Christmas present this year it might not be obvious that you are helping a revolution in sports science. Some of the most popular presents are likely to be mobile phones, games consoles and computer games and the modern stocking filler now contains more sensory technology than an early space mission. The accelerometer chip that prompts your phone to create light-sabre sounds as you swing it is the same technology that we use to help train the world’s best athletes.
Current estimates put the global phone tally at around 5 billion with the latest containing accelerometers, gyroscopes, GPS, electronic compasses and mega pixel cameras (some with video at 120 frames per second or high definition resolution). Modern comsumer technologies sell in staggering volumes, the current ‘fastest selling electronic gadget‘ is Apple’s iPhone 4S, which gained the title after it sold over 1 million units per day in the first few days after launch. Before the iPhone 4S, Microsoft’s Kinect held the top spot, selling 100,000 units per day for 60 days. Before them both Nintendo’s Wii held the title with over 90 million unites sold to date.
The point is that, in science, we use a lot of the devices now common place in phones and consoles. Accelerometers and gyroscopes have been used for many years to measure the acceleration, rotation and inertial forces of moving bodies, particularly in engineering (see ‘The History of the Accelerometer’ by Patrick Walter). The manufacture of these sensors in huge quantities has brought down their cost significantly. Sport is an early adopter and has always used the latest in technologies so expect to see your Christmas present used on an athlete near you very soon.
Microsoft’s Kinect is probably the game changer (sorry for the pun). It uses an infra-red projector to project a pseudo random array of invisible-to-the-eye dots up to a distance of around 10 m. An infra-red camera picks up the dots and complex algorithms use the distortion of the patterns to calculate depth. This is combined with a standard colour camera to give a 3D view of the world. The device detects the gestures of the user and uses them to control a game.
What is really exciting is that the Kinect measures the 3D world and can measure surfaces, track motion and even put a rudimentary skeleton on real-time analysis. All for around $100. Conventional gait labs run into the hundreds of thousands of dollars and while they are much more accurate, they still require you to attach a series of intrusive, reflective markers on the participant, something the Kinect can do without.
We’ve done some initial tests with the Kinect and it appears that it can measure the volume of a torso to around 2% accuracy and the position of the centre of mass to around 0.5%. Joint angles are not quite as good at the moment, particularly for the lower body (the Kinect appears to be optimised for the upper body) but early use shows promise. Apple appears to have taken out a patent on 3D cameras for its iPhone and no doubt other manufacturers will be thinking the same, with the possibility that we will soon be able to measure the 3D world around us.
A phone is not just for Christmas
There is a conference just after Christmas on wearable sensors – not just for sport but for health related uses too. After all, performance improvement is relative: for an elite athlete it might be measured in hundredths of a second while for someone in rehabilitation it might be simply to walk again.
So when you open that present on Christmas day, marvel at the technology within and imagine the possibilities – the chances are there’ll be an app for that before too long.