Sodium Bicarbonate Supplementation Enhances Repeated High-Intensity Interval Training Performance and Time Above 90%...

This study investigated the effects of sodium bicarbonate (SB) supplementation on physiological responses and performance during submaximal exercise, high-intensity interval training (HIT) and repeated Wingate sprints in well-trained cyclists. Twenty-four participants (♂ = 15, maximal oxygen uptake [ $\dot{V}{O}_2$ max] = 72 ± 5 mL·min^-1 kg^-1; ♀ = 9, $\dot{V}{O}_2$ max = 57 ± 6 mL·min^-1 kg^-1) performed one screening and familiarisation session and two experimental sessions in a randomised, double-blind and crossover design. Participants ingested SB (∼0.26 g·kg^-1) or an appearance-matched placebo (PLA) 2 hours before the experimental session. Each session consisted of a step-test protocol followed by five 5 min HIT bouts (3 × 40 s maximal efforts with 60 s recovery at power output (PO) equal to 3 mmol·L^-1 [blood lactate]) and four 30 sec Wingate sprints. Cycling economy and fractional utilisation of $\dot{V}{O}_2$ max were evaluated during a submaximal step test. During HIT bouts, PO was significantly higher in SB (2.0 ± 5.4%, mean difference (MD): 8.1 ± 22.1 W, p = 0.045, ${\eta }_p^2$  = 0.171), accompanied by increased oxygen uptake (MD: 60.1 ± 124.7 mL·min^-1, p = 0.006, ${\eta }_p^2$  = 0.281) and greater time spent above 90% $\dot{V}{O}_2$ max (MD: 23.7 ± 52.6 s, p = 0.012, ${\eta }_p^2$  = 0.246). In the Wingate sprints, cyclists demonstrated significantly greater PO following SB ingestion (2.0 ± 4.7%, MD: 11.6 ± 26.8 W, p = 0.002, ${\eta }_p^2$  = 0.342). This was accompanied by higher blood levels of bicarbonate, pH and lactate (p < 0.001, ${\eta }_p^2$  = 0.557; p < 0.001, ${\eta }_p^2$  = 0.548; p < 0.001, ${\eta }_p^2$  = 0.558, respectively). Cycling economy and fractional utilisation of $\dot{V}{O}_2$ max were unaffected by SB supplementation (p = 0.977 and p = 0.818). SB supplementation increased PO and time above 90% $\dot{V}{O}_2$ max during HIT and PO during repeated Wingate sprints. Whether this translates into superior long-term adaptations, such as enhanced $\dot{V}{O}_2$ max and sprint performance, remains to be investigated.