Plasma Acidosis and Peak Power after a Supramaximal Trial in Elite Sprint and Endurance Cyclists: Effect of Bicarbonate

MILDENHALL, M. J., E. MAUNDER, D. J. PLEWS, M. I. LINDINGER, and S. P. CAIRNS. Plasma Acidosis and Peak Power after a Supramaximal Trial in Elite Sprint and Endurance Cyclists: Effect of Bicarbonate. Med. Sci. Sports Exerc., Vol. 55, No. 5, pp. 932-944, 2023. Purpose: This study aimed to determine whether (i) a plasma acidosis contributes to a reduction of mechanical performance and (ii) bicarbonate supplementation blunts plasma acidosis and arterial oxygen desaturation to resist fatigue during the end spurt of a supramaximal trial in elite sprint and endurance cyclists. Methods: Elite/world-class cyclists (n = 6 sprint, n = 6 endurance) completed two randomized, double-blind, crossover trials at 105%V. O-2peak simulating 3 min of a 4-km individual pursuit, 90 min after ingestion of 0.3 g center dot kg(-1) BMsodium bicarbonate (BIC) or placebo (PLA). Peak power output (PPO), optimal cadence and optimal peak torque, and fatigue were assessed using a 6-s "all-out sprint" before (PPO1) and after (PPO2) each trial. Plasma pH, bicarbonate, lactate(-), K+, Na+, Ca2+, and arterial hemoglobin saturation (SpO(2)(%)), were measured. Results: Sprint cyclists exhibited a higher PPO, optimal pedal torque, and anaerobic power reserve (APR) than endurance cyclists. The trial reduced PPO (PLA) more for sprint (to 47% initial) than endurance cyclists (to 61% initial). Optimal cadence fell from similar to 151 to 92 rpm and cyclists with higher APR exhibited a reduced optimal peak torque. Plasma pH fell from 7.35 to 7.13 and plasma [lactate(-)] increased from 1.2 to 19.6 mM (PLA), yet neither correlated with PPO loss. Sprint cyclists displayed a lesser plasma acidosis but greater fatigue than endurance cyclists. BIC increased plasma [HCO3-] (+6.8 mM) and plasma pH after PPO1 (+0.09) and PPO2 (+0.07) yet failed to influence mechanical performance. SpO(2) fell from 99% to 96% but was unrelated to the plasma acidosis and unaltered with BIC. Conclusions: Plasma acidosis was not associated with the decline of PPO in a supramaximal trial with elite cyclists. BIC attenuated acidbase disturbances yet did not improve arterial oxygen desaturation or mechanical performance at the end-spurt stage.