The quantified olympian

Biometric gadgets are transforming the way the world's elite athletes are trained. These wearable sensors provide on-the-go physiological measurements, which previously required bulky and costly lab equipment. Just as weight-training regimens became popular 40 years ago to build more resilient athletes, wearables are now helping players both improve performance and ward off injury. "I definitely see them as becoming part of everyday training," says Marko Yrjovuori, a biomechanics specialist who trains the Los Angeles Lakers basketball team. Here are some state-of-the-art systems that are changing the game for elite athletes, including a few within reach of dedicated amateurs.