Open AccessChanges in Creatine Kinase and Hormones Over the Course of an American Football Season
Author(s) -
Jason D. Stone,
Andreas Kreutzer,
John D. Mata,
Mason G Nystrom,
Andrew R. Jagim,
Margaret Jones,
Jonathan M. Oliver
Publication year - 2019
Publication title -
journal of strength and conditioning research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.569
H-Index - 128
eISSN - 1533-4287
pISSN - 1064-8011
DOI - 10.1519/jsc.0000000000001920
Subject(s) - football , creatine kinase , athletes , hormone , testosterone (patch) , american football , endocrinology , medicine , zoology , biology , physical therapy , geography , archaeology
Stone, JD, Kreutzer, A, Mata, JD, Nystrom, MG, Jagim, AR, Jones, MT, and Oliver, JM. Changes in creatine kinase and hormones over the course of an American Football Season. J Strength Cond Res 33(9): 2481-2487, 2019-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 nonstarters. Fasting blood samples were obtained from 19 National Collegiate Athletic Association Division I (n = 19; 20 ± 1 years) football athletes over the course of a season beginning before the start of summer off-season conditioning (T1), before (T2) and after preseason (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 before the start of the season (T1, Effect Size [ES] = 0.8) and during preconference (T4; ES = 0.7). Postcamp (T3) testosterone was lower in all players, though greater in starters (starters, 0.0%/0.3%/99.7%; nonstarters, 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 nonstarters may be indicative of greater damage and stress experienced by starters, which may result from a greater number of repetitions.