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Excerpt
The purpose of this study was to determine the effects of 8 weeks training with The SportCord™, an elastic resistance device, on the ventilatory threshold (VT) and muscle fiber type composition. 10 college age males and 16 college age females served as subjects. Muscle biopsies were obtained pre and post from the vastus lateralis m. Myosin ATPase histochemistry was used to determine fiber type composition. Percentage fiber type area was calculated. An incremental cycle ergometer test was performed. VE, VO2, VCO2, RER, VE/VO2, and VE/VCO2 were recorded every 20 seconds. VT was defined as the point where VE/VO2 increased while VE/VCO2 stayed constant. Training consisted of 2-3 training sessions per week. During each session 2 sets each of (right & left) single leg squats and leg extensions were performed to failure with the Sportcord™. Percentage of IIB fibers decreased for both sexes after training; a concomitant increase in percentage of type IIAB fibers was observed. The men also had a significant increase in percentage IIA fibers. The percentage fiber type area did not change for either sex for any fiber type. VO2peak did not change from pre to post. VT occurred at a significantly greater percent of VO2peak (VT%VO2pk) after training. However, VT occurred at a statistically similar absolute and relative VO2. Pre-training, VT%VO2pk was negatively correlated to percentage IIB fiber area (r=−.46, p<.05), it was also positively correlated to percentage type I plus type IIA fiber area (r= .46, p<.05). Neither percentage type I fiber area or percentage type IIA fiber area alone were significantly correlated to VT%VO2pk. These correlations were not significant after training or when represented as percent fiber type. Results suggest that VT%VO2pk may be related to percentage oxidative fiber type area. However, changes in VT%VO2pk with training appear to be independent of changes in muscle fiber type composition.
