Characterizing Biomarkers of Muscle Damage in Collegiate Football Players: A Prospective, Repeated Measures Study.

Background/Objectives: Exertional rhabdomyolysis (ER) is a possibly fatal condition resulting from extreme or novel exercise that causes substantial muscle breakdown. ER has been observed during preseason football; however, prospective research has yet to characterize normal versus ER responses using a repeated measures design. This study characterized ER biomarker responses related to muscle damage, and renal and hepatic stress, after two NCAA Division I preseason football scrimmages. Methods: Following a prospective, repeated measures design, blood and urine samples from 17 players were collected immediately (IPS) and 24 h post-scrimmage (24hPS). A subset (n = 13) provided samples after 48 h of rest as a non-exertion (NE) comparator group. A Comprehensive Metabolic Panel was run on serum samples, and urine samples were analyzed for myoglobin and creatinine. Values were compared with reference ranges, mixed models evaluated time effects, and linear regressions examined associations between CPK and renal and hepatic biomarkers. Results: No participants were diagnosed with ER. A time effect was observed for CPK (p < 0.01), with CPK greater IPS (991.6 ± 560.8 IU/L) compared to NE (267.7 ± 205.3 IU/L), and remaining elevated above reference ranges at 24hPS (739.2 ± 442.6 IU/L). Similar time effects were observed with LDH, AST, and ALT (p < 0.01). Serum creatinine increased above reference values and NE concentrations (p < 0.01). CPK correlated (p < 0.01 for all) with LDH (r = 0.69), serum myoglobin (r = 0.57), creatinine (r = 0.42), AST (r = 0.77), and ALT (r = 0.38). Conclusions: Biomarkers of muscle damage, renal stress, and liver function were higher IPS, with only partial recovery by 24hPS. These findings provide preliminary reference patterns for biomarker fluctuations and support individualized, serial monitoring to identify abnormal responses and promote early detection of ER.