Abstract
0442 Purpose: The aim of this investigation was to determine the effect of varying cycle pedal rates at a constant power output on muscle oxygen desaturation (ΔO2) using near-infrared spectroscopy (NIRS). Methods: Thirteen male untrained cyclists (age = 19.6 ± 1.1yrs., BMI = 24.2 ± 1.7 kg/m2) completed three, seven minute exercise bouts. The bouts used 40, 60, and 80 revolutions per minute at a power output of 100 Watts. NIRS data were collected on the left vastus lateralis continuously for each seven minute bout. Muscle ΔO2 was determined to be the difference (760 mV – 850 mV) between minute seven and baseline. Oxygen consumption (VO2), respiratory exchange ratio (RER) and heart rate (HR) were measured each minute. Pedal rate and brake resistance were monitored continuously. ANOVA's tested for significance in ΔO2, VO2, RER, and HR between each pedal rate using data from the last minute of each exercise bout. Results: There was no significant difference in ΔO2 (−74 ± 171 mV at 40 rpm, −190 ± 95 mV at 60 rpm, and −173 ± 112 mV at 80 rpm) or RER (0.99 ± 0.07 at 40 rpm, 1.02 ± 0.07 at 60 rpm, and 1.03 ± 0.08 at 80 rpm) between the pedal rates. HR was higher (p < 0.05) at 80 rpm (ie. 165 ± 18 bpm) than 40 rpm (ie. 146 ± 21 bpm). VO2 was higher (p < 0.05) at 80 rpm (ie. 2.57 ± 0.26 L.min−1) than 40 rpm (ie. 2.14 ± 0.24 L.min−1) and 60 rpm (ie. 2.27 ± 0.17 L.min−1). Conclusion: The results indicate that variation in cycle pedal rates from 40 to 80 rpm at a constant power output did not have a differentiated effect on muscle oxygen desaturation. As HR and VO2 were significantly higher at the 80 rpm than 40 rpm pedal rate, leg muscle ΔO2 appeared to be independent of total body oxygen consumption.
Published Version
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