A new piece of wearable workout technology goes to the bottom of the matter — the bottom of the feet, that is — to help runners train optimally and avoid injury. Athletes can slip the sensor-filled Nurvv Run insoles into their shoes and, through the trackers and coaching app (a kind of telehealth on the run), receive biomechanics data and feedback on their gait, foot strike, step length, cadence, speed, pronation and training load. Each lightweight sole contains 16 sensors, developed with sport science experts, engineers, and athletes in the U.K.