Biochemical and Hormonal Responses during an Intercollegiate Football Season JAY R. HOFFMAN, JIE KANG, NICHOLAS A. RATAMESS, and AVERY D. FAIGENBAUM Department of Health and Exercise Science, The College of New Jersey, Ewing, NJ ABSTRACT HOFFMAN, J. R., J. KANG, N. A. RATAMESS, and A. D. FAIGENBAUM. Biochemical and Hormonal Responses during an Intercollegiate Football Season. Med. Sci. Sports Exerc., Vol. 37, No. 7, pp. 1237–1241, 2005. 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 nonstarters (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 preseason 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. Key Words: ATHLETES, ENDOCRINE, SPORTS, PERFORMANCE, TESTOSTERONE, CORTISOL R esearch on American football has primarily focused on the descriptive characteristics of players at vari- ous levels of competition (8,9,23) and the efficacy of various resistance training protocols on strength and athletic performance improvements (13,16). Studies examining the physiological response to American football are quite lim- ited. A previous study from our laboratory examined per- formance, biochemical, and endocrine changes during a competitive football game (12). Results from that study were unique in that both biochemical and endocrine markers of muscle damage (myoglobin and aspartate aminotransfer- ase) and stress (cortisol) were elevated at the end of the game, suggesting some degree of muscle damage. However, creatine kinase concentrations (an enzyme that is frequently used to assess muscle damage) following exercise were not elevated. It was hypothesized that the repeated traumas that occur during a season of football may have provided some degree of sensitization of the muscles. As a result, the extent of the disruption of the skeletal muscle membrane was likely minimized, allowing for only the smaller molecules (e.g., myoglobin) to leak out. Considering that no longitudinal study of physiological adaptations in American football athletes during a competitive season is known, this can only be speculative. Research focusing on physiological and performance changes in competitive intercollegiate athletes, specifically with participants in team sports such as football, is rather uncommon. Limited studies on soccer players and swim- mers have demonstrated that endocrine changes during a season of competition, while suggestive of a more catabolic state, did not correspond with any changes in performance (2,6). Similarly, wrestling has also been shown to have a potent effect on endocrine function during a competitive season (19,24). Although changes in testosterone and cor- tisol may reflect the physiological stress of prolonged train- ing, the additional stress associated with weight reduction for many wrestlers appeared to exacerbate the endocrine response to a season of competition. However, the training during a competitive football season is quite different com- pared with those sports. Competitions are less frequent, practice schedules are more consistent, and players are gen- erally attempting to maintain their body mass. Address for correspondence: Jay R. Hoffman, Ph.D., FACSM, CSCS*D, Department of Health and Exercise Science, The College of New Jersey, PO Box 7718, Ewing, NJ 08628-0718; E-mail: hoffmanj@tcnj.edu. Submitted for publication November 2004. Accepted for publication February 2005. 0195-9131/05/3707-1237/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE ® Copyright © 2005 by the American College of Sports Medicine DOI: 10.1249/01.mss.0000170068.97498.26 1237