Changes in Creatine Kinase and Hormones Over the Course of an American Football Season

Abstract

The purpose of this study was to examine changes in creatine kinase and hormones over the course of an entire season of American football. A secondary purpose was to determine differences between starters and non-starters. Fasting blood samples were obtained from nineteen National Collegiate Athletic Association Division I (n = 19; 20 ± 1 years) football athletes over the course of a season beginning prior to the start of summer off-season conditioning (T1), before (T2) and after pre-season (T3) football camp, with remaining samples taken throughout the competitive season (T4-T8). A magnitude-based inference approach was used to define outcomes. Testosterone was higher in starters prior to the start of the season (T1, Effect Size [ES] = 0.8) and during pre-conference (T4; ES = 0.7). Post-Camp (T3) testosterone was lower in all players, though greater in starters (starters, 0.0%/0.3%/99.7%; non-starters, 0.2%/2.9%/96.9%). An increase cortisol relative to baseline (T1) was observed in starters early in season (T4, ES = 0.7; T5, ES = 0.5). Creatine kinase was elevated at all time-points in all athletes, with starters having higher circulating levels throughout season. These data demonstrate that changes in hormonal markers may be experienced over a season of football and differ by playing status. Differences between starters and non-starters may be indicative of greater damage and stress experienced by starters, which may result from a greater number of repetitions.

Sex Differences in Physiological Stress Induced by a Long-Lasting Adventure Race: A Prospective Observational Analytical Study

“…The association between muscle injury and cortisol levels is supported by the literature [42]. Nonetheless, unlike cortisol levels, CK and LHD were higher in males than in females after the race.…”

The Relationship Between Handball Players and Alcohol and Smoking Habits

“…We may assume that earlier/later involvement into a sport activity can be related to alcohol consumption and there are numerous reasons to support this assumption. Experienced players are better at coping with stress ( Stone et al, 2017 ), which is one of the most frequent causes leading to alcohol consumption among athletes. Future research should consider the connection between alcohol and sports experience more closely.…”

Association between Muscle Damage and Head Impacts in High School American Football

“…Similarly, post-game blood samples, collected within 1 h after the end of the game, were well-within the serum CK-MM half-life of 15 h [40]. This sampling interval is a major strength of this study design and allowed us to investigate the associations between pre-to post-game changes in CK-MM to head impact kinematics and physical exertion unlike Stone et al [41] and Kraemer et al [42] who collected blood samples 48 h post-game and 17-18 h post-game, respectively. These long intervals ( > 15 h) between post-game and sample collections can lead to inaccurate measurements of skeletal muscle-specific CK-MM due to the hybridization of the three CK isoenzymes (muscle, muscle-brain, brain) in the peripheral circuitry [40].…”

“…Kraemer et al found no significant changes and no significant differencs between starters and nonstarters in CK activity across a college football season; however, an analysis of covariance revealed that the number of plays sustained in the game prior to the last blood sample time point was a significant cofactor [42]. Stone et al also investigated CK levels throughout a college football season and found that starters exhibited increased CK activity relative to nonstarters at all but one of the study time points, which they attributed to the increased repetitions that the starters were exposed to in both practices and games [41]. In the current study, since all subjects in our small sample were active members that played in nearly every game included in the study design, we did not dichotomize the players into "starters" and "nonstarters."…”