Aerobic Exercise May Speed Concussion Recovery in Teens

Damian McNamara

February 14, 2019

Contrary to traditional recommendations for prolonged, prescribed rest after a sports-related concussion, new research suggests that a regimen of low-level aerobic exercise may speed recovery and reduce symptoms.

In a randomized clinical trial, researchers assessed 103 adolescents within 1 week of experiencing a concussion. Those assigned to aerobic exercise recovered after a median of 13 days compared with 17 days for those assigned to a placebo-like stretching regimen, which translated into a statistically significant difference.

"I'm a team doctor. We had athletes who were not recovering in a typical timeframe, so we came up with this idea of using subthreshold exercise to help them recover," principal investigator John J. Leddy, MD, of UBMD Orthopaedics and Sports Medicine, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, told Medscape Medical News.

"That was in people with prolonged symptoms — and it worked," he said.

The findings were published online February 4 in JAMA Pediatrics.

Questioning "Rest Is Best"

Historically, clinicians instructed youth experiencing sports-related concussions to rest until all symptoms resolved.

"That's fine for the 75% to 80% of people who recover normally, within a week or two," Leddy said. "But what about those who don't? Do you just tell them to keep resting and wait until it goes away?"

He said the investigators also questioned the strength of evidence behind the "rest-is-best approach," noting it is based on animal research and consensus guidelines.

The current multicenter study builds on the findings of a prior "small, uncontrolled initial foray into using subthreshold exercise to treat adult patients with prolonged symptoms, people who were experiencing post-concussion symptoms for weeks or months," Leddy said.

"In the last 10 years, there have been more and more studies — either observational or with prescribed exercise — showing that in fact, not only is it not harmful, it may be beneficial," he added.

However, "to move the field you need to do randomized clinical trials," he said.

The investigators randomly assigned male and female athletes aged 13 to 18 years to either subthreshold aerobic exercise (n = 52) or a stretching regimen (n = 51). An experienced sports medicine physician diagnosed their concussion using International Concussion in Sport Group criteria.

"We started working with adolescents because it soon became clear that they take longer to recover than other groups," Leddy said. "Nobody really knows why that is."

Participants were recruited from September 2015 to June 2018. The baseline evaluation included a cognitive assessment and completion of a concussion symptom questionnaire. Participants also underwent a standard physical exam and a graded exercise tolerance assessment using the Buffalo Concussion Treadmill Test (BCTT).

This assessment allowed researchers to determine an individualized 80% threshold for aerobic exercise based on the participant's heart rate. Participants repeated the BCTT weekly for up to 30 days.

Quicker Recovery

The aerobic exercise group wore heart rate sensors and fitness trackers to monitor their heart rates. They were instructed to perform daily exercise on a stationary bike or a treadmill at home or in a gym under supervision.

Each session lasted 20 minutes or until their symptoms increased 2 points or more on a 10-point visual analog scale, at which point they stopped. The investigators also told them to rest otherwise and not to play any contact sports or participate in gym class or team practice.

The stretching group also wore heart rate monitors during each session. They received the same instructions about resting otherwise. Both groups received the same amount of attention.

The aerobic exercise group recovered in a median of 13 days (interquartile range [IQR], 10 - 18.5) vs 17 days (IQR, 13 - 23) for the stretching group (P = .009).

There was a protective trend against athletes developing delayed recovery in the aerobic exercise group. "This was a potentially crucial outcome, given the burden of social and academic problems during prolonged recovery in this age group," the researchers write.

Participants reported symptoms online each evening between 7 pm and 10 pm using the Post-Concussion Symptom Scale. There was no significant difference between groups regarding compliance; 83.8% of the exercise group and 86.6% of the stretching group completed daily symptom reports (P = .16).

The trial lasted 30 days, after which any athlete still experiencing symptoms received interdisciplinary treatment. This delayed-recovery group included two participants in the exercise group and seven in the stretching cohort.

There were no adverse events in the study, although one participant was "a near miss," the researchers report. This athlete became "severely symptomatic" on the BCTT and decided to withdraw from the study before randomization.

Confidence Booster

"The results of this study should give clinicians confidence that moderate levels of physical activity, including prescribed sub-symptom threshold aerobic exercise, after the first 48 hours following sports-related concussion, can safely and significantly speed recovery," the investigators write.

The researchers caution that the findings should not be generalized to younger children, adults with risk factors for heart disease, or patients with nonsports-related concussions. They also emphasize the importance of carefully monitoring exercise so patients do not exceed their individual threshold for exacerbating concussion symptoms.

"This is not equivalent to a return to sport-specific play; rather, it is a nearly active intervention intended to improve recovery to the point where it is safe for the athlete to begin the graduated process of returning to his or her sport," the investigators note.

Why aerobic exercise might work remains unknown. "We think exercise actually restores control to the autonomic nervous system, which is clearly affected by concussion," Leddy said. Aerobic exercise could help increase blood flow to the muscles, brain, or both, he added.

Increased neuroplasticity is another possibility. Exercise may increase brain-derived neurotrophic factor, which repairs neurons and promotes hippocampal growth, he said.

"Exercise has several [beneficial] effects, but again we need to prove that," Leddy added.

Paradigm Shift?

"Early on there was a hefty amount of skepticism" about whether aerobic exercise post-concussion could be effective, Leddy said. "I think the skepticism has come down now."

Several professional medical societies recently stopped endorsing the 'rest is best' for everyone strategy. For example, such a consensus emerged from the 5th International Conference on Concussion in Sport.

As reported by Medscape Medical News, the Centers for Disease Control and Prevention recently included this perspective in its evidence-based guidelines.

In addition, the American Academy of Pediatrics updated its guidance on sports-related concussions in a statement that describes the evolution from elimination of all activity in the days following a concussion to an emphasis on reduction of activity. 

"You have to find the sweet spot between not doing something other than lying in a dark room under the covers and going back to full participation in sports," Leddy said. "The trick is really finding that sweet spot."

Leddy and colleagues are now doing a "bigger, better designed study" in collaboration with Harvard University and the University of Pennsylvania. They will report results on an intent-to-treat analysis, "which is more how medicine is practiced in real life versus in a research setting," he said.

The participants in the next study will have more accurate heart rate monitors. One goal is to try to determine the minimal dose of exercise that confers post-concussion benefits.

"Landmark Study"

"Research on exercise and concussion has been in transition, and this is a landmark study that may shift the standard of care toward the use of rehabilitative exercise to decrease the duration of concussion symptoms," Sara P.D. Chrisman, MD, Department of Pediatrics, University of Washington, and the Harborview Injury Prevention and Research Center in Seattle, writes in an accompanying editorial.  

Chrisman also notes some study limitations. The researchers excluded adolescents with depression, anxiety, and attention-deficit/hyperactivity disorder out of concern that such diagnoses were associated with greater risk for persistent concussive symptoms.

"However, these diagnoses are also particularly prevalent in youth seen for concussion, and not including them means we cannot draw conclusions regarding whether aerobic exercise is an effective treatment for youth with concussions who exhibit mental health symptoms or whether we should instead specifically target mental health interventions in these individuals, as has been done in previous studies," she writes.

The researchers also did not measure physical activity in an objective way, and "thus it is impossible to estimate the dose of exercise required to elicit a treatment outcome."

Future research, she adds, could address some unanswered questions. For example, what is the earliest timeframe post-concussion to start exercise safely? Is it possible for patients to exercise too frequently or too intensely; and if so, what are the risks? Is exercise beneficial for all patients post-concussion?

"We look forward to following this line of research as it propels us toward continued improvement in the management of concussion," Chrisman writes.

The study was funded by grants from the National Institute of Neurological Disorders and Stroke of the National Institutes of Health (NIH) and the NIH National Center for Advancing Translational Sciences. Leddy and Chrisman have reported no relevant financial relationships.

JAMA Pediatr. Published online February 4, 2019. Abstract, Editorial

Follow Damian McNamara on Twitter: @MedReporter. For more Medscape Neurology news, join us on Facebook and Twitter.

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