The E39 shirt features a thin disc, containing the sensors, a power source, Bluetooth transmitter, and memory storage. Coupled with fabric electrodes, the system is capable of monitoring cardiac activity, anaerobic threshold, aerobic capacity, and other vitals that indicate an athlete’s performance and health. “That’s the trend in both medicine and sports,” Brian Russell, Zephyr’s CEO, tells MIT’s Technology Review. “Because you can measure it, you can personalize it. “You can put them in the tight training zone for peak fitness and no injury.” “Players know that if they share data, they get better television coverage and a better contract,” says Russell. Plus, athletes seems to like the shirt’s futuristic appearance, disc and all. “They say they feel like Iron Man,” he adds.