A fall in intramyocellular [H+] is associated with muscle fatigue due to 1) an inhibition of glycogenolysis and glycolysis [8], 2) increased muscular K+ release, 3) lesser contractility of the heart muscle [9], 4) inhibition of the sarcoplasmatic calcium release [10] and 5) inhibition of the actin-myosin interactions [11]. Thus, delaying the fall in intramyocellular pH might postpone the fatigue process and prolong intact muscle function. Indeed, our results showed that the ingestion of NaHCO3 induced metabolic alkalosis, which in turn enhanced T lim at CP and thus improved high-intensity exercise in the range of 10 to 20 min duration. As hypothesized, T lim at CP could be increased with

NaHCO3 supplementation. I-BET151 in vivo This is in contrast to the theoretical model, which states that an intramyocellular metabolic steady state exists at exercise intensities up to CP. However, our results support the notion that CP overestimates the metabolic steady state [4, 5]. Furthermore, our result that NaHCO3 increased T lim at CP extends previous findings showing that NaHCO3 supplementation increases exercise above CP relative to placebo [14, 29]. In the latter studies, short high-intensity tests, during which intramyocellular pH falls rapidly from the beginning of exercise, were completed. SB202190 concentration During these

types of tests, the finite work capacity above CP (W ′ ) is drawn on after the start of exercise and becomes reduced. In light of our findings, these results might be interpreted to mean that NaHCO3 simply increases W’. However, Vanhatalo et al.[23] showed that NaHCO3 does not increase W’ during a 3-min all-out test, and concluded that changes in intramyocellular pH might not influence W’ in this particular test setting, and that for short all-out exercise, [PCr] dynamics is more important in determining W’. In our constant-load trials at CP, W’ was supplied to a large extent by anaerobic glycolysis. Therefore, we assume that NaHCO3 supplementation

increases W’ in conditions where acidification occurs during exercise. buy Abiraterone Our result that the estimated V̇ O2 slow component was not different between the two interventions lends further credence to this notion, although the influence of NaHCO3 on the V̇ O2 slow component remains ambiguous (reduction: [30]; no change: [31]). In our study, the identical V̇ O2 slow component for both, the NaHCO3 and placebo condition, indicated that V̇ O2peak was attained at the same point in time. Based on the fact that the depletion of W’ coincides with the attainment of V̇ O2peak[32], our results indicate that NaHCO3 ingestion did not increase the rate of W’ utilization but rather W’ itself. Further support for our assumption comes from another study, where average power in a 60 min cycling time trial was found to be higher with NaHCO3 as compared to placebo [33].