Exercise performance and neuromuscular activity at a fixed level of RPE following manipulation of peripheral physiological status

Sarah Browne, Andrew Renfree

Abstract

PURPOSE: to analyse the effect of manipulation of peripheral physiological status on performance and neuromuscular activity during cycling at a fixed level of RPE. METHODS: following familiarisation trials, seven well trained individuals completed two exercise trials following ingestion of 0.2g.kg-1 NaHCO3 or a CaCO3 placebo which were performed in a randomised and blind manner. During exercise participants were required to cycle at exercise intensity equivalent to their perception of an RPE of 16 on the Category Ratio Scale. Blood pH was measured pre- and post-exercise, and power output, EMG activity in the active musculature, and heart rate were recorded continuously throughout exercise. Exercise was terminated when power output fell below 80% of the average recorded over the first 3 minutes of each trial. RESULTS: pre-exercise pH was higher following NaHCO3 ingestion, but post-exercise values did not differ between NaHCO3 and placebo trials. Exercise duration was 21% longer following NaHCO3 than the placebo, but no significant differences were found in power output or heart rate between trials at any point. EMG activity was higher throughout NaHCO3 trials. CONCLUSIONS: the findings of this study suggest that NaHCO3 ingestion enhanced exercise duration by allowing an increased volume of exercise to be performed prior to individuals reaching individual critical threshold values for pH. Lower neuromuscular activity despite a similar power output following NaHCO3 suggests that perceptions of effort may be based on absolute work rates rather than afferent physiological feedback, and that the work rate is achieved through regulation of efferent neural drive.


Keywords

Perceived exertion; Electromyography; Sodium bicarbonate

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DOI: https://doi.org/10.4100/jhse.2013.83.07