Evaluating the effects of caffeine and sodium bicarbonate, ingested individually or in combination, and a taste-matched placebo on high-intensity cycling capacity in healthy males

M. F. Higgins, Susie Wilson, Cameron Hill, Mike J. Price, Michael J. Duncan, Jason Tallis

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This study evaluated the effects of ingesting sodium bicarbonate (NaHCO3) or caffeine individually or in combination on high-intensity cycling capacity. In a counterbalanced, crossover design, 13 healthy, noncycling trained males (age: 21 ± 3 years, height: 178 ± 6 cm, body mass: 76 ± 12 kg, peak power output (Wpeak): 230 ± 34 W, peak oxygen uptake: 46 ± 8 mL·kg−1·min−1) performed a graded incremental exercise test, 2 familiarisation trials, and 4 experimental trials. Trials consisted of cycling to volitional exhaustion at 100% Wpeak (TLIM) 60 min after ingesting a solution containing either (i) 0.3 g·kg−1 body mass sodium bicarbonate (BIC), (ii) 5 mg·kg−1 body mass caffeine plus 0.1 g·kg−1 body mass sodium chloride (CAF), (iii) 0.3 g·kg−1 body mass sodium bicarbonate plus 5 mg·kg−1 body mass caffeine (BIC-CAF), or (iv) 0.1 g·kg−1 body mass sodium chloride (PLA). Experimental solutions were administered double-blind. Pre-exercise, at the end of exercise, and 5-min postexercise blood pH, base excess, and bicarbonate ion concentration ([HCO3−]) were significantly elevated for BIC and BIC-CAF compared with CAF and PLA. TLIM (median; interquartile range) was significantly greater for CAF (399; 350–415 s; P = 0.039; r = 0.6) and BIC-CAF (367; 333–402 s; P = 0.028; r = 0.6) compared with BIC (313: 284–448 s) although not compared with PLA (358; 290–433 s; P = 0.249, r = 0.3 and P = 0.099 and r = 0.5, respectively). There were no differences between PLA and BIC (P = 0.196; r = 0.4) or between CAF and BIC-CAF (P = 0.753; r = 0.1). Relatively large inter- and intra-individual variation was observed when comparing treatments and therefore an individual approach to supplementation appears warranted.
Original languageEnglish
Pages (from-to)354-361
JournalApplied Physiology, Nutrition, and Metabolism
Issue number4
Early online date17 Mar 2016
Publication statusPublished - Apr 2016



  • caffeine
  • sodium bicarbonate
  • alkalosis
  • metabolic buffers
  • cycling

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