Dr. Donal O’Gorman’s lab has conducted a study comparing the physiological responses during cycling at different pedalling rates. They found a greater rate of oxygen consumption (~15%) and energy expenditure when cycling at 95-rpm required when compared with the same exercise at 65-rpm. This was in spite of the fact that total work, determined by watts on the bike, was the same for both trials. This finding prompted his research group to conduct more detailed experiments investigating the possible mechanisms behind this difference.
In so doing, they obtained skeletal muscle biopsies before and after bicycle exercise at different contraction frequencies. One approach was to measure surface electromyography to determine if there were differences in the electrical activity of the muscle. The second approach and the purpose of my project will be to determine if there was a greater recruitment of muscle fibres during exercise at the higher contraction frequency. If so, this might explain why more oxygen was consumed. To answer this question, I will be quantifying the muscle fibre composition of each sample using immunohistochemistry and examining the glycogen content of the same fibres using a Periodic acid–Schiff stain. If the glycogen content was decreased in more fibres following exercise
at 95-rpm it would indicate that these fibres had been recruited during the exercise. However, if there were no differences in muscle glycogen per individual fibre it would suggest that other factors, maybe within the individual fibres, might account of the increased oxygen consumption.
