Physiological and Performance Effects of Caffeine Gum Consumed During a Simulated Half-Time by Professional Academy Rugby Union Players

J Strength Cond Res. 2020 Jan;34(1):145-151. doi: 10.1519/JSC.0000000000002185.


Russell, M, Reynolds, NA, Crewther, BT, Cook, CJ, and Kilduff, L. Physiological and performance effects of caffeine gum consumed during a simulated half-time by professional academy rugby union players. J Strength Cond Res 34(1): 145-151, 2020-Despite the prevalence of caffeine (CAF) as an ergogenic aid, few studies have examined the use of caffeinated gums, especially during half-time in team sports. The physiological (blood lactate and salivary hormone concentrations) and performance (repeated sprints and cognitive function) effects of consuming CAF gum during a simulated half-time were examined. Professional academy rugby union players (n = 14) completed this double-blind, randomized, counterbalanced study. After pre-exercise measurements, players chewed a placebo (PLC) gum for 5 minutes before a standardized warm-up and completing repeated sprint testing (RSSA1). Thereafter, during a 15-minute simulated half-time period, players chewed either CAF (400 mg; 4.1 ± 0.5 mg·kg) or PLC gum for 5 minutes before completing a second repeated sprint test (RSSA2). Blood lactate, salivary testosterone and cortisol concentrations, and indices of cognitive function (i.e., reaction time and Stroop test) were measured at baseline, pre-RSSA1, post-RSSA1, pre-RSSA2, and post-RSSA2. Sprint performance was not affected by CAF (p = 0.995) despite slower sprint times after the first sprint of both RSSA tests (all p < 0.002). After half-time, salivary testosterone increased by 70% (+97 ± 58 pg·ml) in CAF vs. PLC (p < 0.001), whereas salivary cortisol remained unchanged (p = 0.307). Cognitive performance was unaffected by time and trial (all p > 0.05). Although performance effects were absent, chewing CAF gum increased the salivary testosterone concentrations of professional rugby union players over a simulated half-time. Practitioners may, therefore, choose to recommend CAF gum between successive exercise bouts because of the increases in salivary testosterone observed; a variable associated with increased motivation and high-intensity exercise performance.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Athletic Performance / physiology*
  • Caffeine / administration & dosage*
  • Chewing Gum
  • Cognition
  • Cross-Over Studies
  • Double-Blind Method
  • Football / physiology*
  • Humans
  • Hydrocortisone / analysis
  • Lactic Acid / blood
  • Male
  • Performance-Enhancing Substances / administration & dosage*
  • Saliva / chemistry
  • Testosterone / analysis
  • Warm-Up Exercise
  • Young Adult


  • Chewing Gum
  • Performance-Enhancing Substances
  • Lactic Acid
  • Caffeine
  • Testosterone
  • Hydrocortisone