Muscle Damage, Soreness, and Stress Over 7-weeks of Pre-season Training In NCAA D1 Female Swimmers

In 2014, three female swimmers were hospitalized with symptomatic exertional rhabdomyolysis (Stanfa et al., 2016). PURPOSE: To serially monitor and assess relationships between skeletal muscle damage, upper and lower body soreness, and physiological stress during the first seven weeks of high volume training in collegiate female swimmers. METHODS: 23 female NCAA D1 swimmers presented to the lab six times during 7-weeks of pre-season training. Blood was drawn at six timepoints for measurement of serum creatinine kinase (CK), myoglobin (MYO) and a complete metabolic panel. Serum cortisol (C), testosterone (T) and T/C ratio were assessed at Weeks 1 (baseline), 4 and 7. Upper body soreness (US) and lower body soreness (LS) were assessed, at the six timepoints that blood was drawn, using a visual analogue scale (0-10-inch unmarked scale). A repeated measures ANOVA with a Bonferroni correction were performed, with data reported as means±SD. Correlation analyses performed with significance set at p<0.05. RESULTS: Weekly training load consisted of: 88% swimming, 6% running, and 6% weight training which gradually increased from 16 hours to 20 total training hours/week over the first seven weeks of training. Significant changes were noted in CK (135±68; 446±723; 171±83; 202±80; 180±100; 206±170; p=0.01), US (1.5±1.8; 3.9±1.7; 3.3±1.8; 5.4±1.6; 6.1±1.8; 3.7±2.0; p<0.0001), LS (1.3±1.5; 5.0±2.2; 3.4±1.8; 5.0±1.9; 4.8±1.8; 4.1±2.0; p<0.0001), cortisol (19±10; 15±6; 11±5ng/dL; p<0.0001), and T/C ratio (2.4±2.3; 3.0±1.8; 4.1±2.8; p=0.0003) but not in MYO (39±20; 63±141; 29±18; 30±17; 24±4ng/mL; 29±14ng/mL; p=0.32) or testosterone (33±14; 37±14; 36±14 ng/dL; p=0.29). Significant correlations noted between CK vs. MYO (r=0.84), alanine aminotransferase (r=0.21), and aspartate aminotransferase (r=0.49) when data were combined, but largely driven by an outlier with CK=3558 ng/mL and MYO=691ng/mL at Week 2 (first training week). CONCLUSION: Muscle damage in collegiate female swimmers remained largely within the normal range (CK<200U/L) on average, but was highly variable between individuals. No correlations noted between muscle damage (CK, MYO) and (upper and lower) body soreness, at moderate (2-6) ratings of muscle soreness. Serum cortisol declined over training, promoting an anabolic hormonal environment.