Performance, biochemical, and endocrine changes during a competitive football game

Purpose: This study represents the first time that anaerobic power performance was examined during an actual intercollegiate American football game. In addition, biochemical and endocrine responses also were examined to assess the physiological stress imposed by this competitive contest. Methods: Twenty-one members of a NCAA Division III football team were divided into two groups. Group one (ST) were starters (N _ 11). The second group (RS) consisted of red-shirt players (N _ 10). Blood samples were obtained 24 h (Pre1) and 2.5 h (Pre2) before the game and within 15 min of game conclusion (IP). Anaerobic power measures were recorded approximately 10 min before kickoff (pre) and following the first (Q1), second (Q2), third (Q3), and fourth (Q4) quarters. Results: Peak force (PF) and power (PP) in both squat and countermovement jumps decreased (P _ 0.05) from pre to Q2 in both ST and RS; however, all variables returned to baseline levels by Q4. When averaged across trials, PF and PP in both jumps were greater (P _ 0.05) in ST than RS. No significant changes in testosterone concentrations with respect to time or between groups were seen. Cortisol concentrations were significantly higher for ST at IP than RS. No significant changes in creatine kinase, alanine aminotransferase, urea, or uric acid were observed in either group from Pre2 to IP. In addition, no between group differences were seen in these variables. Myoglobin and aspartate aminotransferase significantly increased from Pre2 to IP in ST, and a significant difference in myoglobin concentrations was seen between the groups at IP. Conclusions: Performance, biochemical, and endocrine changes in these NCAA Division III football players reflected the stress and muscle damage that occurs as a result of a competitive American football game.