Understanding Heart Rate Variability
SELF magazine featured insight from Assistant Professor of Exercise Science Alexander Rothstein, Ed.D., in an article about heart rate variability (HRV), a measure of the variation in time between heartbeats. Rothstein explained that HRV reflects how well the nervous system is balancing stress and recovery, but it shouldn’t override how you actually feel. Day-to-day swings are normal—especially after poor sleep, tough workouts, or stress—and a single low reading doesn’t necessarily mean you’ll perform poorly. Instead of reacting to isolated numbers, Rothstein stressed paying attention to long-term trends and using HRV as one data point among many.
“If you are generally well rested but then get one bad night of sleep, your HRV will likely be all over the place—but chances are you’ll still be able to play a great game of tennis the next day… It would really come down to how you felt, rather than what your HRV suggested,” he said.