COMMENTARY

A New Way to Predict and Prevent Athletic Injury

Laird Harrison

Disclosures

February 05, 2015

Lowering the Risk for Athletic Injuries

Mike Esco learned the hard way what "readiness" means.

Around 2001, Esco, a bodybuilder in Montgomery, Alabama, 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 a quest for an objective test that can predict how well an apparently healthy athlete will perform on a given day.

After several years and a doctorate in exercise physiology, he may have found it: heart rate variability. "It appears to be a very promising tool," he says.

Esco, now an assistant professor of exercise physiology at the University of Alabama in Tuscaloosa, is not alone in his quest. At universities and technology companies around the world, researchers are exploring multiple measures of readiness. In addition to heart rate variability, they are analyzing how people move, either through a prescribed series of positions or in a practice or game.

Their findings apply not only to athletes but also to firefighters, soldiers, dancers, and anyone else concerned about physical performance.

Heart Rate as a Gauge of Physical Fitness

Trainers have long used simple heart rate—the number of heart beats per minute—to gauge a subject's fitness. By contrast, heart rate variability is a measure of the change in time between heart beats.

"We think of the distance between each beat as consistent," says Esco. "But in reality, that's not the case. The more variability, the better. That's indicative of a restful state."

Heart rate variability is a marker of how the autonomic nerve system controls the cardiovascular system, he explains. Greater variability indicates a more parasympathetic state, and less variability indicates a more sympathetic state.

Normally, the sympathetic arm of the autonomous nervous system should be active during exercise, and the parasympathetic arm of the system should be active during recovery.

Heart rate variability can help improve training regimens in three ways, say Esco. First, it may predict cardiac events. Second, compared from one week to the next, it may indicate more precisely than simple heart rate how a person's overall fitness is changing. And third, it can show whether an individual is ready to exercise on a particular day.

Someone in a relatively sympathetic state may not have completed recovery and therefore may not be ready for more exercise, says Esco. "Heart rate variability is so sensitive that 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."

A few studies have found that greater heart rate variability can predict better performance[1] and that changing training regimens may be more successful if the intensity undulates based on heart rate variability.[2,3]

In a study presented at the American College of Sports Medicine 2014 annual meeting, an international team of researchers found that soccer players training with muscle fatigue or contracture had less variable heart rates and were much more likely to be injured.[4]

Though researchers are still working out the exact relationship between heart rate variability and the risk for musculoskeletal injury, it makes sense that there should be a correlation, says Esco.

"The cardiovascular system is completely integrated with all the others, including the musculoskeletal system," he says. "If it's not recovered enough to deliver the optimum nutrients in blood on a particular day, the musculoskeletal system is not going to work properly on that day."

Makers of a variety of commercial products, such as wearable monitors and smartphone applications, are already touting their products as useful in adjusting training regimens.

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