The Effect of Pedaling Frequency and Stretching on FAT/CHO Crossover Point

Abstract

An acute bout of stretching will decrease muscular strength, power and endurance, which could possibly be due to an increased inhibition of motor neurons. Animal research has well established that slow motor neurons are activated first and are more oxidative. Unfortunately, research has been inconclusive as to whether the stretch induced inactivation of motor units also has speed specificity like that of activation; therefore it is possible a stretch induced inactivation would alter the amounts of carbohydrates(CHO) and fat(FAT) used at slower speeds. PURPOSE: To determine if stretching changes substrate utilization during exercise, yielding different FAT/CHO crossover points. METHODS: 15 Men and women (age 22±4.5y; mean±SD) college aged participants (VO2Max= 31.9±5.5mL·kg-1·min-1) were recruited for the study. Each participant was tested on a Velotron® cycle ergometer with and without pre-cycling stretching. Stretching consisted of five different passive static stretches which were held for fifteen seconds and repeated three times. An assistive stretching session followed with the same five stretches held for fifteen seconds and repeated three times. The non-stretched condition consisted of ten minutes of quiet sitting. Following the stretch treatment participants pedaled at 50 revolutions per minute (RPM) for 6 minute stages. The exercise workload started at 15 watts(W) and increased by 15W until an RER of 0.95 was reached, ensuring the crossover point (RER = 0.85) had been surpassed. RESULTS: Mean VO2 (L/min) corresponding to the crossover point was 0.51±0.37 L/min and 0.58±0.51 L/min for stretching and non-stretching conditions at 50 RPM, respectively (p>0.5). The results revealed no difference (P>0.5) in the crossover point, demonstrating no difference in substrate utilization with and without stretching prior to cycling at a slower pedal rate. CONCLUSION: These data suggest that prior static and active stretching does not elicit a stretch induced inactivation that can alter substrate usage.