Purpose: Changes in biochemical indices of muscle damage and hormonal markers of stress were examined during a competitive intercollegiate football season.
Methods: Twenty-one members of an NCAA Division III football team volunteered to serve as subjects. Eleven of these subjects were starters (ST) and 10 were non-starters (NS). All subjects reported to the Human Performance Laboratory on five separate occasions for blood draws. The first testing session (T1) occurred 1 d before the start of pre-season training camp, the second testing session (T2) occurred at the end of training camp (10 d later), and the other three testing sessions occurred at weeks 3 (T3), 7 (T4), and 11 (T5) of the competitive season.
Results: Significant elevations in creatine kinase (CK) were seen from T1 to T2 in both ST and NS. ST had significantly higher CK concentrations at T2 than NS. CK concentrations for both groups returned to baseline levels by T3 and remained constant for the rest of the season. No significant between-group differences were seen in myoglobin (MB), testosterone (TE), cortisol (C), or the testosterone/cortisol ratio (T/C) during the season. A significant main effect for time was seen for C and T/C. C concentrations were significantly lower at T2 than at T1, T3, T4, and T5. Similar changes were also seen for T/C.
Conclusion: CK elevations seen during T2 appear to reflect the high intensity and physical nature of training camp. However, biochemical and endocrine responses during a season of intercollegiate football competition suggest a degree of sensitization (contact adaptation) of the muscles relating to the repeated traumas occurring during the season.