The influence of sodium bicarbonate on maximal force and rates of force development in the triceps surae and brachii during fatiguing exercise

The effect of metabolic alkalosis on fibre-specific maximal force production and rates of force development (RFD) has been previously investigated in animal models, with evidence suggesting an improved capacity to rapidly develop force in fast- compared to slow-twitch muscle. We have attempted to model in vivo the fatigue profile of voluntary and involuntary maximal force and RFD in the triceps’ surae and brachii after sodium bicarbonate (NaHCO3) ingestion. In a double-blind, 3-way repeated measures design participants (n = 10) ingested either 0.3 g·kg−1 NaHCO3 (ALK) or equivalent calcium carbonate (PLA) prior to 2-min of continuous (1 Hz) supramaximal stimulation (300 ms at 40 Hz) of the triceps’ surae or brachii, with maximal voluntary efforts (MVT) coupled with direct muscle stimulation also measured at baseline, 1-min and 2-min. Metabolic alkalosis was achieved in both ALK trials but was not different between muscle groups. Regardless of condition, involuntary torque declined nearly 60% in the triceps brachii (P < 0.001) and ∼30% in the triceps surae (P < 0.001). In all trials there was a significant decline in normalised involuntary RFD (P < 0.05). MVT declined nearly 28% but was not different between conditions (P < 0.01), and although declining nearly 21% in voluntary RFD (P < 0.05) there was no difference between PLA and ALK in either muscle group (P = 0.93). NaHCO3 exhibited no effect on the fatigue observed between representative fibre-type muscle groups on maximal voluntary and involuntary torque or rates of torque development during and after 2-min of tetanic stimulation.