Abstract
BackgroundCaffeine and sodium bicarbonate ingestion have been suggested to improve high-intensity intermittent exercise, but it is unclear if these ergogenic substances affect performance under provoked metabolic acidification. To study the effects of caffeine and sodium bicarbonate on intense intermittent exercise performance and metabolic markers under exercise-induced acidification, intense arm-cranking exercise was performed prior to intense intermittent running after intake of placebo, caffeine and sodium bicarbonate.MethodsMale team-sports athletes (n = 12) ingested sodium bicarbonate (NaHCO3; 0.4 g.kg−1 b.w.), caffeine (CAF; 6 mg.kg−1 b.w.) or placebo (PLA) on three different occasions. Thereafter, participants engaged in intense arm exercise prior to the Yo-Yo intermittent recovery test level-2 (Yo-Yo IR2). Heart rate, blood lactate and glucose as well as rating of perceived exertion (RPE) were determined during the protocol.ResultsCAF and NaHCO3 elicited a 14 and 23% improvement (P < 0.05), respectively, in Yo-Yo IR2 performance, post arm exercise compared to PLA. The NaHCO3 trial displayed higher [blood lactate] (P < 0.05) compared to CAF and PLA (10.5 ± 1.9 vs. 8.8 ± 1.7 and 7.7 ± 2.0 mmol.L−1, respectively) after the Yo-Yo IR2. At exhaustion CAF demonstrated higher (P < 0.05) [blood glucose] compared to PLA and NaHCO3 (5.5 ± 0.7 vs. 4.2 ± 0.9 vs. 4.1 ± 0.9 mmol.L−1, respectively). RPE was lower (P < 0.05) during the Yo-Yo IR2 test in the NaHCO3 trial in comparison to CAF and PLA, while no difference in heart rate was observed between trials.ConclusionsCaffeine and sodium bicarbonate administration improved Yo-Yo IR2 performance and lowered perceived exertion after intense arm cranking exercise, with greater overall effects of sodium bicarbonate intake.
Highlights
Fatigue during high-intensity intermittent exercise is complex and multifaceted
Between group comparisons revealed that blood [lactate] values were similar between PLA and CAF, but higher (P < 0.01) for the NaHCO3 trial compared to PLA and CAF trials at exhaustion (Figure 2A)
At 5 min into recovery Yo-Yo IR2 blood [lactate] was reduced in the PLA trial when compared to CAF and NaHCO3 (7.2 ± 2.2 vs. 8.5 ± 2.3 and 9.1 ± 1.9 mmol.L−1; P < 0.05, respectively) whereas CAF and NaCHO3 were similar at this time point (P > 0.05)
Summary
Fatigue during high-intensity intermittent exercise is complex and multifaceted. Early speculation regarding the aetiology of fatigue commends that high rate of lactic acid production and a concomitant fall in blood and muscle pH [1], which may have multiple indirect and direct impairing effects on centrally and peripherally mediated fatigue-resistance. Caffeine and sodium bicarbonate (NaHCO3) are two supplements frequently consumed to elicit ergogenic effects on high-intensity exercise performance [2]. Effects of caffeine on intense intermittent exercise performance have for example been studied by Stuart et al [3] demonstrating improved repeated sprint performance during a simulated rugby game trial. Team-sport athletes improved both total work and mean power output during an intermittent cycle sprint protocol [4] and Yo-Yo IR2 performance by 16% after caffeine intake [5]. Caffeine and sodium bicarbonate ingestion have been suggested to improve high-intensity intermittent exercise, but it is unclear if these ergogenic substances affect performance under provoked metabolic acidification. Blood lactate and glucose as well as rating of perceived exertion (RPE) were determined during the protocol
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