title: Salivary cortisol and α-amylase responses to repeated bouts of downhill running.
abstract: OBJECTIVE
  To determine the hypothalamic-pituitary-adrenal (HPA) axis and sympathoadrenal (SA) system response to repeated bouts of downhill running.
  
  
  METHODS
  Eleven active but untrained males (age: 19.7 ± 0.4 y; VO2peak 47.8 ± 3.6 ml/kg/min) performed two 60 min bouts of downhill running (-13.5% gradient), separated by 14 days, at a speed eliciting 75% of their VO2peak on a level grade. Saliva samples were collected before (baseline), after, and every hour for 12 h and every 24 h for 6 days after each run. Salivary cortisol and α-amylase levels were measured as markers of the HPA axis and SA response, respectively. Results were analyzed using repeated measures ANOVA (12 h period: 2 × 14; 24 h intervals 2 × 7, P ≤ 0.05) with Tukey post-hoc tests where appropriate. Paired samples t-tests were used to compare collapsed data vs. baseline measurements.
  
  
  RESULTS
  There were no significant group × time interactions for cortisol or α-amylase for the hourly samples up to 12 h after each run, nor for the 24 h samples up to 6 days later. The 24 h samples for α-amylase showed a significant group effect between runs (Run 1: 69.77 ± 7.68 vs. Run 2: 92.19 ± 7.67 U/ml; P = 0.04). Significant time effects were measured for both cortisol (decreased 2 h to 12 h post-run) and α-amylase (elevated immediately after, 1 h and 2 h post-run) (P < 0.001).
  
  
  CONCLUSIONS
  The 24 h period group effect for salivary α-amylase suggested an adaptation in the sympathoadrenal system that may alter the systemic inflammatory response to exercise-induced muscle damage but may also reflect enhanced mucosal immunity.
authors.affiliation: Discipline of Biokinetics, Exercise and Leisure Sciences, School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Mckune
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Bach
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Semple
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Dyer
mesh_terms: D000222:Adaptation, Physiological; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D008297:Male; D010913:Pituitary-Adrenal System / Q000378:metabolism; D012420:Running / Q000502:physiology*; D012463:Saliva / Q000737:chemistry; D055291:Salivary alpha-Amylases / Q000378:metabolism*; D013312:Stress, Physiological; D013564:Sympathetic Nervous System / Q000378:metabolism; D055815:Young Adult
chemical_list: D055291:Salivary alpha-Amylases; D006854:Hydrocortisone