Mike Esco learned the hard way what “readiness” means for an athlete.
A bodybuilder, Esco was making a transition to power lifting and wanted to compete. Feeling confident one day, he hit the gym so hard that he badly injured his back. The experience launched him on quest for an objective test that can predict how well an apparently healthy athlete will perform on a given day.
After several years and doctorate in exercise physiology, he may have found it: a heart rate variability test.
“It appears to be a very promising tool,” Esco told me when I interviewed him for Medscape Medical News.
A Heart Rate Variability Test for Performance
Trainers have long used heart rate, the number of heart beats per minute, to gauge a subject’s fitness. By contrast, a heart rate variability test measures the change in time between heart beats.
“We think of the distance between each beat as consistent,” said Esco, now an assistant professor of exercise physiology at the University of Alabama. “But in reality that’s not the case.”
Broadly speaking, your nervous system functions in two modes: fight-or-flight and feed-or-breed.
When you exercise, your system kicks into the fight-or-flight mode (known to wonks as activating the sympathetic arm of the autonomic nerve system). Your system funnels energy to muscles so you can run, jump, swing, hit and do all the other things athletes want to do.
In feed-or-breed mode (activating the parasympathetic arm), the energy goes into digestion, repairing and rebuilding muscle and other body parts, or — if the opportunity arises — into sex.
But the way you feel doesn’t always match the mode your nervous system is in. You can feel hungry or horny and still be in flight-or-fight. And you can feel like running a marathon and be in feed-or-breed. That’s why researchers have been looking for an objective measurement.
In fight-or-flight mode, your heart beats more steadily, like a metronome. In feed-or-breed mode, it beats more irregularly.
“Heart rate variability is so sensitive,” said Esco. “It changes throughout each day. It can relate to how an athlete trains or whether they broke up with their girlfriend, or a lot of things.”
Some studies show that athletes will perform best on those days when their heart beats are most variable, and worst on those days when their heart beats are most regular.
A Heart Rate Variability Test for Injury
According to Esco, no one has yet shown that a heart rate variability test can predict sports injuries such as his. But at least one study showed a correlation muscle fatigue and heart rate variability and between muscle fatigue and injury in soccer players.
It makes sense. Your whole body, including your bones and muscles, depend on your heart and nerves. If your heart has not recovered from exercise, it’s reasonable to think you are at greater risk of, say, spraining your ankle or tearing your rotator cuff.
In addition to predicting who is ready to compete on a day-to-day basis, some studies show, a heart rate variability test may help you improve your training regimen on a week to week basis.
I haven’t seen much specific research on these products, or tried them out myself. But I hope to learn more in the near future. I’ll let you know as soon as I do.
In the meantime, I’d have to have a cold heart not to be carried along by Mike Esco’s enthusiasm.
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