Effect of induced alkalosis on performance during a field-simulated BMX cycling competition

Abstract

Objectives: The aim of the present study was to test the effect of sodium bicarbonate (NaHCO₃^-) ingestion on performance during a simulated competition on a Bicycle Motocross (BMX) track.

Design: Double-blind cross-over study.

Methods: Twelve elite male BMX cyclists (age: 19.2±3.4 years; height: 174.2±5.3cm; body mass: 72.4±8.4kg) ingested either NaHCO3- (0.3g.kg^-1 body weight) or placebo 90min prior to exercise. The cyclists completed three races in a BMX Olympic track interspersed with 15min of recovery. Blood samples were collected to assess the blood acid-base status. Performance, cardiorespiratory, heart rate variability (HRV) as well as subjective variables were assessed.

Results: The main effect of condition (NaHCO₃^- vs. placebo) was observed in pH, bicarbonate concentration and base excess (p<0.05), with a significant blood alkalosis. No changes were found in time, peak velocity and time to peak velocity for condition (p>0.05). The HRV analysis showed a significant effect of NaHCO₃^- ingestion, expressed by the rMSSD30 (root mean square of the successive differences) (p<0.001). There was no effect of condition on oxygen uptake, carbon dioxide production, or pulmonary ventilation (p>0.05). Finally, there was no effect of condition for any subjective scale (p>0.05).

Conclusions: We present here the first field condition study to investigate the effect of bicarbonate ingestion over performance in BMX discipline. The results showed that NaHCO₃^--induced alkalosis did not improve performance in a simulated BMX competition in elite BMX cyclists, although future studies should consider the effects of NaHCO3- on autonomic function as a component of recovery.

Keywords: Acidosis; Athletic performance; Ergogenic aids; Heart rate variability; Sodium bicarbonate.