May 2016

Out on a limb: Stumping for SR in sports


By Jordana Bieze Foster, Editor

Platelet-rich plasma injections. Kinesiology tape. Foam rolling. Compression garments. Blood-flow restriction training. Elite athletes have always been at the leading edge of the latest tech­niques believed to help speed recovery from injury, often long before they’ve been subjected to rigorous scientific study.  So why isn’t the sports world buzzing about stochastic resonance (SR)?

SR is a process in which introducing low levels of “noise” to a system heightens sensory signal recognition; for example, introducing subsensory electrical stimulation to the plantar surface of the feet via a vibrating insole heightens a person’s sensorimotor perception in ways that have been associated with improvements in balance and gait. Some of the most interesting recent work in this area has been done at the Wyss Institute for Biologically Inspired Engineering at Harvard Medical School in Boston, by authors who have summarized a portion of their work in this issue (see “Using subsensory noise to improve balance, gait,” page 37.)

As you might imagine, the most obvious applications for this type of technology involve people with sensory impairment related to aging or conditions such as stroke or diabetic neuropathy; in those populations it could help reduce the risk of falls and fall-related injury. But the Wyss researchers have found that SR also has positive effects in young, healthy individuals, helping to enhance balance control in response to fatiguing exercise. Since fatigue is associated with increased injury risk in otherwise healthy people, the findings suggest SR could potentially reduce that risk.

But it gets better. The Wyss team has also found that the use of SR in young, healthy, recreational athletes is associated with improved performance on an agility task. The .12-second improvement in time may not seem like much, but the authors pointed out that, when the same agility drill was performed at the 2015 National Football League Combine, .13 seconds separated the fastest time from the eighth-fastest time.

Now, I suspect that most sports leagues would consider the use of vibrating insoles during competition an unfair advantage—something I wouldn’t want to be accused of advocating. But the findings also appear to support the idea of using SR to improve rehabilitation of athletes after an injury.

For example, although strength deficits and asymmetries are often associated with poor outcomes after injury, multiple studies have also shown that simply strengthening a weak muscle doesn’t translate to improved biomechanics—the body has to learn how to use that stronger muscle. Doesn’t it seem like using SR to enhance sensorimotor function might be a logical way to try to bridge that gap?

Granted, SR has not yet been formally studied in elite athletes. But a lack of published evidence has hardly ever stopped elite athletes—and the practitioners they work with—from trying absolutely anything to speed recovery after an injury. And what’s known about SR so far suggests it has the potential to do just that.

It might be the best rehab intervention nobody in sports is talking about. At least not yet.

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