Alterations in energy expenditure have been observed following moderate and severe traumatic brain injury (TBI) in animals and humans. However, few data exist characterizing how mild TBI, specifically concussion, affects whole-body energy expenditure. The purpose of this study was to examine resting metabolic rate (RMR) following sport concussion in university and high school student-athletes.
Concussed participants were recruited from a university and local high schools. Concussion diagnosis was made by an athletic trainer or physician. Participants could have no other concurrent injury (e.g., fracture). RMR was determined by indirect calorimetry (VMax Metabolic Cart) with a ventilated hood < 72 hours following a diagnosed concussion (T1), 7 days after T1 (T2), and 7 days after T2 (T3). Predicted RMR (pRMR) was also calculated using 3 validated equations: Harris-Benedict (HB), Mifflin-St. Jeor (MSJ) and Schofield (SCH). These equations were used to examine the magnitude of change in RMR following concussion. Measured and predicted values were compared at each time point using percentages ([RMR/pRMR] x 100). Changes over time in measured RMR were assessed using a repeated measures ANOVA.
Twelve concussed participants (aged 17.7 + 2.15 years, BMI 21.8 + 2.94) completed T1 at 1.8 + 0.84 days post-injury. There were 3 participants of each sex from each academic setting (university and high school). Measured RMR percent of pRMR was below 100% at each time point post-concussion (T1: HB = 53% + 7.6%, MSJ = 55% + 8.6%, SCH = 53% + 9.1%; T2: HB = 54% + 6.6%, MSJ = 56% + 6.7%, SCH = 53% + 8.1%; and T3: HB = 57% + 8.5%, MSJ = 59% + 9.6%, SCH = 57% + 9.0%). Additionally, measured RMR did not change over time (T1 = 909 + 226.0 kcal, T2 = 905 + 154.5 kcal, T3 = 975 + 266.7 kcal; F2 = 1.348, p = 0.28).
Concussed student-athletes appear to have suppressed resting metabolism of about 40% following injury when compared with validated prediction equations. Although future studies are needed to confirm our findings by comparing concussed participants to healthy-matched controls, these preliminary data suggest use of prediction equations to estimate concussed student-athletes’ dietary energy requirements should be used with caution.