title: Dose effects of caffeine ingestion on acute hormonal responses to resistance exercise.
abstract: OBJECTIVE
  The purpose of this study was to examine the dose effects of caffeine on acute hormonal responses to resistance exercise (RE).
  
  
  METHODS
  Twelve university males who regularly performed RE participated in this study. Subjects performed one repetition maximum (1RM) test and four treatments in a counterbalanced order: high dose (HD, 6 mg.kg(-1)), medium dose (MD, 4 mg.kg(-1)), low dose (LD, 2 mg.kg(-1)), and placebo (PLA). Subjects ingested caffeine 1 hour before RE and then performed RE (2 exercises, 3 sets of 10 repetitions at 75% of 1RM). Blood samples were collected before caffeine intake (pre-60), immediately before RE (pre-exe), and 0, 15, 30 min post RE (P0, P15, and P30, respectively) for analysis of serum testosterone, cortisol, insulin, glucose, lactate, and free fatty acid (FFA). Each experiment was separated by 7 days. Statistical analysis of two-way analysis of variance with repeated measures was applied. Statistical significance was set at α=0.05.
  
  
  RESULTS
  The concentrations of FFA (pre-exe) were significantly elevated following the HD, MD, and LD ingestions of caffeine. The concentrations of testosterone (P0, P15, and P30) and cortisol (pre-exe, P0, P15, and P30) at HD were significantly increased. However, the responses of insulin (P0 and P15) at HD and MD were significantly decreased.
  
  
  CONCLUSIONS
  The results of this study indicate that high doses of caffeine increase the responses of testosterone and cortisol. Moreover, moderate and high doses of caffeine attenuate the insulin responses.
authors.affiliation: Department of Recreation Sport and Health Promotion Pingtung University of Science and Technology Pingtung, Taiwan - licar1980@hotmail.com.
authors.forename: B H
authors.initials: BH
authors.lastname: Wu
mesh_terms: D000284:Administration, Oral; D002110:Caffeine / Q000008:administration & dosage*; D018592:Cross-Over Studies; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007328:Insulin / Q000097:blood*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D055070:Resistance Training; D013739:Testosterone / Q000097:blood*; D055815:Young Adult
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019344:Lactic Acid; D002110:Caffeine; D013739:Testosterone; D006854:Hydrocortisone