Recreational athletes who sustained a concussion had significant increases in heart rate and resting systolic blood pressure within 48 hours of the injury, according to a small study of college students.
By day three, though, their heart rate and blood pressure returned to normal.
Lead researcher Jacqueline John L. Dobson, PhD, of Georgia Southern University, and colleagues published their results online in the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology on Feb. 1.
Each year, there is an estimated 1.6 million to 3.8 million concussions in the U.S., according to the researchers, although they noted the incidence is likely much higher because many concussions are unrecognized or unreported.
The study included 23 college students, including 12 who suffered a concussion while participating in a sport as well as 11 control participants who were matched by sex, height and mass. The participants were involved in recreational activities, but they did not participate in intercollegiate athletics or actively engage in an intensive exercise training program.
All of the participants performed breathing, standing and Valsalva autonomic tests on four occasions: acute (within 48 hours post-concussion), subacute (24 hours after the acute test), week 1 (seven days after the concussion) and week 2 (14 days after the concussion).
During the acute period, concussed participants had significant increases in resting systolic blood pressure, heart rate and systolic blood pressure perturbations during standing as well as 90 percent in systolic blood pressure normalization times following Valsalva-strain. All of those measures returned to normal during the subacute, week 1 and week 2 tests.
The researchers noted that the study’s most significant limitation was its small sample size. It took them two years to recruit the 12 concussed participants. They also mentioned several of the analyses were considerably constrained by high coefficient of variation scores and by power values that were below the desired minimum of 0.8.
“While all current concussion guidelines recommend no return to participation on the day of injury, these results further support the progressive return to participation protocols thus preventing individuals from returning to activities while experiencing autonomic dysfunction,” the researchers wrote. “The results also mirror the recovery timeline of balance and cognitive testing following a concussion, which suggests autonomic impairment results from the concussion. These results expand the existing literature on autonomic dysfunction post-concussion and provide a foundation for future investigations that can utilize a within-subjects design incorporating baseline/pre-morbid data. The advantage of using autonomic tests such as forced breathing, standing and the Valsalva maneuver is that they are highly reliable and valid, non-invasive and they require less physical exertion than most forms of exercise.”