Determining aerobic capacity at symptomatic threshold in individuals with persistent concussion symptoms

Abstract

ContextResearch on exercise for concussion rehabilitation is gaining considerable attention. However, unless adequately prescribed, exercise can induce/exacerbate symptoms and impede neurologic recovery. Therefore, the primary purpose of this investigation was to determine the metabolic rate and aerobic capacity at symptomatic threshold in concussed individuals.MethodsThirty-seven concussed individuals (men = 14, women = 23; 22.97 years, ±5.13) completed a graded exercise test on a stationary bike using a modified Balke protocol. Symptoms (SCAT-4) and physical exertion (Borg Scale) were periodically monitored throughout testing, which ceased at the induction/exacerbation of symptoms. Aerobic capacity was assessed using an estimated VO2max calculation (ACSM, 2015). Descriptive and correlation statistics were computed with an apriori alpha level of 0.05.ResultsWe observed that symptoms were induced/exacerbated at a mean power output of 95.24W (±34.30), which corresponded to a mean estimated VO2max of 21.29 (±5.84) mL/kg/min and a mean metabolic equivalent of 6.08 (±1.67) METs. No significant differences between men and women were observed. Interestingly, neither total number of symptoms, total symptom score (SCAT-4), nor self-report pre-test cardiorespiratory fitness level (Huet questionnaire) correlated with aerobic capacity at symptomatic threshold (p = 0.05).ConclusionsOur results help to establish the symptomatic threshold in concussed individuals during exercise. Importantly, we did not find a significant correlation between cardiorespiratory fitness and symptom threshold, suggesting a fundamental change in underlying physiology induced by concussion. These findings can be used to design safer graded exercise protocols that aim to enhance rehabilitative efficacy. Further, MET conversions may provide a useful tool in guiding rehabilitation of concussed individuals in every day activities. Our data indicate that concussed individuals would benefit from initiating physical activity at an intensity level below the metabolic and aerobic capacity thresholds described herein.