Alison Kreideweis sat nervously on the edge of a treadmill at Finish Line Physical Therapy in New York City, on Dec. 1. She’d volunteered to help demo a new wearable device that measures an athlete’s lactate threshold, but slipping on the BSX Insight was the easy part—the device, which uses near-infrared light to measure blood oxygen levels in muscle, tucks into a compression sleeve worn on the calf. BSX Athletics president Dustin Freckleton wanted to compare the old and his new lactate threshold tests side-by-side, which meant drawing her blood at three-minute intervals as she ran.
“Do nerves play any part in this?” Kreideweis asked. “Affecting test results?”
An athlete’s lactate threshold is the pace or power they can achieve before lactic acid starts to build up in their muscles. This lactic acid is produced when muscle fibers can no longer get sufficient oxygen for aerobic respiration, and must generate their energy anaerobically. The build-up causes the burn felt in muscles when exercising at high intensity, and above the lactate threshold the athlete will begin to fatigue quickly.