Evaluating Associations Between Postconcussion Physical Activity and Brain Neurometabolite Concentrations in the Posterior Cingulate Gyrus

Objective To examine the association between brain neurometabolite concentrations and physical activity (PA) volume after adolescent concussion. Methods We performed a longitudinal study of adolescents (13-18 years) with concussion. At an initial visit (visit 1; within 21 days of injury), participants rated their symptoms using the Post-Concussion Symptom Inventory (PCSI) and underwent magnetic resonance spectroscopy (MRS) to quantify neurometabolite concentrations in the posterior cingulate gyrus (PCG). Metabolites of interest were glutathione (GSH), glutamate-glutamine (Glx), total choline (tCho), and myo-inositol (mI). Following visit 1, participants were provided with wrist-worn activity monitors for the subsequent 14 days to track steps/day. They repeated MRS evaluation within 5 days of receiving medical clearance to return to sports (visit 2). We compared neurometabolite concentrations between visits, then used linear regression to investigate how PA was associated with neurometabolite concentrations at each visit independently. Results Twenty-seven adolescents underwent MRS scans (15.8 ± 1.3 years; 56% female; assessed 11.7 ± 4.2 and 37.3 ± 16.1 days postinjury) and n = 16 completed PA monitoring. Neurometabolite concentrations did not differ between visits 1 and 2 ( P > .20) before accounting for PA. After controlling for symptom severity, glutamate-glutamine (β=407.5; 95% CI = -6.49, 821.47; P = .053) and total choline (β= 3953.79; CI = -38.47, 7946.05; P = .052) were marginally, but nonsignificantly, associated with PA volume. PA volume during the monitoring period was not significantly associated with unadjusted neurometabolite concentrations at visit 2 ( P > .40). Conclusions Neurometabolite concentrations were marginally associated with subsequent PA volume. These findings indicate that MRS may provide useful information about how PA and brain neurochemistry are associated during concussion recovery.