Abstract
PURPOSE: To investigate the effects of ingesting branched-chain amino acids (BCAA) prior to and during prolonged self-paced cycling on performance and neuromuscular fatigue.
METHOD: Eighteen recreationally active and healthy men (mean±SD age: 24.7±4.8 years old; mass 67.1±6.1 kg; height: 171.7±4.9 cm) completed three sessions. During the first session, participants cycled to exhaustion at a workload corresponding to a fixed blood lactate concentration (3mmol.L-1) and total work performed recorded. The next two cycling trials were completed in randomized order and consisted of self-paced cycling to complete a fixed amount of work (based on first session) with ingestion of either BCAAs (14mg/kg bodyweight) or a placebo (PLA) solution. To assess muscular and neuromuscular fatigue, maximal voluntary contraction (MVC) torque, muscle Voluntary Activation Level (VAL) and Peak Doublet (PD) were measured at pre-, post- and 20-min post-exercise with a maximal superimposed electrical stimulation (doublet stimulations) applied.
RESULTS: Time to complete the fixed amount of work was significantly less reduced with ingestion of BCAAs (PLA: 4266.6±192.4 sec; BCAA: 3978.7±166.7 sec; p=0.04). There was a significant main effect of time on MVC, with the MVC being significantly lower at the point of exhaustion (reduced by 24.0±4.5 Nm; p0.001) and 20-min post-exercise (15.6±4. Nm; p=0.003) when compared to the pre-exercise values. There was no significant interaction (condition x time: p=0.998) or difference in MVC between conditions (p=0.281). Similarly, there was a significant main effect of time on VAL and PD, with each being significantly lower (compared to pre-exercise values) at the point of exhaustion (VAL: -9.6±2.1%; p0.001; PD: -18.7±5.9 Nm; p=0.006) and 20-min post-exercise (VAL: -7.7±2.1%; p=0.003; PD: -14.4±5.1 Nm; p=0.013) but no significant interaction (both condition x time: p≥0.520) or difference in MVC between conditions (both p≥0.519).
CONCLUSION: Ingestion of BCAAs significantly improved cycling performance among recreationally active male participants without any notable changes in either central or peripheral fatigue markers.