The influence of alkalosis on repeated high-intensity exercise performance and acid–base balance recovery in acute moderate hypoxic conditions

Abstract

PurposeExacerbated hydrogen cation (H+) production is suggested to be a key determinant of fatigue in acute hypoxic conditions. This study, therefore, investigated the effects of NaHCO3 ingestion on repeated 4 km TT cycling performance and post-exercise acid–base balance recovery in acute moderate hypoxic conditions.MethodsTen male trained cyclists completed four repeats of 2 × 4 km cycling time trials (TT1 and TT2) with 40 min passive recovery, each on different days. Each TT series was preceded by supplementation of one of the 0.2 g kg−1 BM NaHCO3 (SBC2), 0.3 g kg−1 BM NaHCO3 (SBC3), or a taste-matched placebo (0.07 g kg−1 BM sodium chloride; PLA), administered in a randomized order. Supplements were administered at a pre-determined individual time to peak capillary blood bicarbonate concentration ([HCO3−]). Each TT series was also completed in a normobaric hypoxic chamber set at 14.5% FiO2 (~ 3000 m).ResultsPerformance was improved following SBC3 in both TT1 (400.2 ± 24.1 vs. 405.9 ± 26.0 s; p = 0.03) and TT2 (407.2 ± 29.2 vs. 413.2 ± 30.8 s; p = 0.01) compared to PLA, displaying a very likely benefit in each bout. Compared to SBC2, a likely and possible benefit was also observed following SBC3 in TT1 (402.3 ± 26.5 s; p = 0.15) and TT2 (410.3 ± 30.8 s; p = 0.44), respectively. One participant displayed an ergolytic effect following SBC3, likely because of severe gastrointestinal discomfort, as SBC2 still provided ergogenic effects.ConclusionNaHCO3 ingestion improves repeated exercise performance in acute hypoxic conditions, although the optimal dose is likely to be 0.3 g kg−1 BM.

Effects of daily ingestion of sodium bicarbonate on acid-base status and anaerobic performance during an altitude sojourn at high altitude: a randomized controlled trial

“…The primary finding of the study was that chronic NaHCO 3 ingestion had a considerable impact on acid-base balance, which resulted in a higher alkalotic state; however, chronic NaHCO 3 ingestion did not significantly influence PTSR-related performance outputs and associated physiological responses. A higher alkalotic acid-base balance prior to exercise under hypoxic conditions has been reported to be related to higher performance output and higher maximum blood lactate values after highintensity exercise [11,16,19]. The suggested mechanism underlying the increased [H + ] buffering from intramuscular to extramuscular compartments may lead to improved protection of intramuscular pH and increased anaerobic energy provision and glycogen utilization [16,50].…”

“…Feriche Fernandez-Castanys et al [22], Hauswirth et al [23], and McLellan et al [24] all described increased or constant exercise performance under acute altitude conditions in hypoxic chambers compared with sea-level performance in subjects receiving alkalizing agent supplements prior to exercise. In addition, Deb et al [11,19] and Gough et al [16] reported positive effects of NaHCO 3 under acute moderate hypoxic conditions at simulated altitude during intermittent and repeated high-intensity exercise. They conclude that NaHCO 3 ingestion may offer an ergogenic strategy to mitigate hypoxia-induced declines in exercise performance.…”

“…In normoxic conditions, NaHCO 3 is proposed to enhance anaerobic exercise performance by increasing the availability of blood [HCO 3 − ], thereby strengthening the physiochemical buffering capacity to reduce the rate of hydrogen cation ([H + ]) production during exercise [11,14,15]. However, while the results of some studies have suggested that significant increases in [H + ] may impair subsequent exercise performance by reducing the capacity for muscle force production [16,17], the results of other studies suggest that exercise performance may be unaffected by disturbances in acid-base balance [18]; thus, there remains no consensus in the literature regarding the roles of acid-base status in anaerobic exercise performance and skeletal muscle fatigue. In addition, it has been suggested that the relative increase in glycolytic flux under hypoxic conditions increases [H + ] production, which may be the underlying mechanism for the beneficial effect of NaHCO 3 ingestion under hypoxic conditions [16,19].…”

“…However, while the results of some studies have suggested that significant increases in [H + ] may impair subsequent exercise performance by reducing the capacity for muscle force production [16,17], the results of other studies suggest that exercise performance may be unaffected by disturbances in acid-base balance [18]; thus, there remains no consensus in the literature regarding the roles of acid-base status in anaerobic exercise performance and skeletal muscle fatigue. In addition, it has been suggested that the relative increase in glycolytic flux under hypoxic conditions increases [H + ] production, which may be the underlying mechanism for the beneficial effect of NaHCO 3 ingestion under hypoxic conditions [16,19]. Furthermore, the removal of [H + ] may be inhibited and the blood [HCO 3 − ]-buffering capacity may be reduced [16,19], due to the proposed lower [HCO 3 − ] concentrations present under hypoxic conditions [8].…”

“…In addition, it has been suggested that the relative increase in glycolytic flux under hypoxic conditions increases [H + ] production, which may be the underlying mechanism for the beneficial effect of NaHCO 3 ingestion under hypoxic conditions [16,19]. Furthermore, the removal of [H + ] may be inhibited and the blood [HCO 3 − ]-buffering capacity may be reduced [16,19], due to the proposed lower [HCO 3 − ] concentrations present under hypoxic conditions [8].…”