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Effects of chronic NaHCO₃ ingestion during interval training on changes to muscle buffer capacity, metabolism, and short-term endurance performance

School of Human Movement and Exercise Science, The University of Western Australia, Perth, Australia

Submitted 6 December 2005 ; accepted in final form 8 March 2006

This study determined the effects of altering the H⁺ concentration during interval training, by ingesting NaHCO₃ (Alk-T) or a placebo (Pla-T), on changes in muscle buffer capacity (m), endurance performance, and muscle metabolites. Pre- and posttraining peak O₂ uptake (O_{2 peak}), lactate threshold (LT), and time to fatigue at 100% pretraining O_{2 peak} intensity were assessed in 16 recreationally active women. Subjects were matched on the LT, were randomly placed into the Alk-T (n = 8) or Pla-T (n = 8) groups, and performed 8 wk (3 days/wk) of six to twelve 2-min cycle intervals at 140–170% of their LT, ingesting NaHCO₃ or a placebo before each training session (work matched between groups). Both groups had improvements in m (19 vs. 9%; P < 0.05) and O_{2 peak} (22 vs. 17%; P < 0.05) after the training period, with no differences between groups. There was a significant correlation between pretraining m and percent change in m (r = –0.70, P < 0.05). There were greater improvements in both the LT (26 vs. 15%; P = 0.05) and time to fatigue (164 vs. 123%; P = 0.05) after Alk-T, compared with Pla-T. There were no changes to pre- or postexercise ATP, phosphocreatine, creatine, and intracellular lactate concentrations, or pH_i after training. Our findings suggest that training intensity, rather than the accumulation of H⁺ during training, may be more important to improvements in m. The group ingesting NaHCO₃ before each training session had larger improvements in the LT and endurance performance, possibly because of a reduced metabolic acidosis during training and a greater improvement in muscle oxidative capacity.

alkalosis; lactate threshold; time to fatigue

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