The primary outcome was number of days to recovery since the date of injury. This was defined as symptom resolution to normal (as evaluated by a physician blinded to the study group) and by the patient’s ability to exercise to exhaustion without symptom exacerbation on the BCTT. Secondary outcomes measured the proportion of patients with delayed recovery (defined as recovery requiring > 30 days) and daily symptom scores.
Of 165 patients meeting the inclusion criteria, 52 patients were excluded prior to randomization (12 patients chose not to participate, 39 were excluded for lack of symptoms, and 1 withdrew due to severe symptoms on the BCTT). A total of 113 were randomized to either group, and 103 patients completed the study (10 patients did not complete the study or had another illness during the intervention). The study analysis included 52 patients in the aerobic exercise group and 51 in the placebo-like stretching group. The study was powered to detect a significant difference in recovery time.
Patients were about equally divided by sex, with a mean age of 15 years. Patients who had no previous concussion made up 50% of the aerobic group and 57% of the stretching group. The average time since injury was similar in the aerobic and stretching groups (4.9 days and 4.8 days, respectively). The aerobic exercise group recovered in a median of 13 days (interquartile range [IQR] = 10-18.5 days) compared with a median of 17 days (IQR = 13-23 days) for the stretching group (P = .009). The incidence of delayed recovery (> 30 days) was higher in the stretching group (n = 7) compared with the aerobic exercise group (n = 2) but was not statistically significant. Daily symptom reporting occurred at a high rate in both groups, with patients stating that they performed their prescribed exercise 89% of the time. No adverse events were reported.
WHAT’S NEW
First high-quality study to support evidence for early light activity
This is the first high-quality study of subsymptom threshold exercise for SRC. Its findings add to the growing body of evidence that early engagement in light aerobic activity that does not provoke symptoms (but not fully returning to sports activity) can aid in recovery from an SRC.
CAVEATS
Narrow study population limits application of findings
It is unclear if subsymptom threshold exercise is safe and effective in adolescents with a history of multiple concussions, as those with more than 3 concussions were excluded from this study. Additionally, patients with comorbidities such as ADHD, depression, anxiety, or learning disorders were not included in this study, which limits the application of these findings. The generalizability of this study is limited in younger children, adults, those with increased cardiovascular risk, and in patients with concussions that are not sports related.
CHALLENGES TO IMPLEMENTATION
More real-world studies needed to confirm benefit
The majority of adolescent athletes in this study completed the subsymptom threshold exercise in a monitored environment with trainers, heart rate monitors, and access to equipment, limiting the study’s generalizability. Additionally, physicians need to be familiar with the BCTT to assign heart rate goals and assess improvement. The study environment may be feasible for some but not others. Studies evaluating real-world settings with athletes self-monitoring for symptom threshold with stepwise evaluations are needed and may be more broadly applicable.
ACKNOWLEDGEMENT
The PURLs Surveillance System was supported in part by Grant Number UL1RR024999 from the National Center for Research Resources, a Clinical Translational Science Award to the University of Chicago. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.
