Title: Limitations to work capacity during low- and high-load multi-joint resistance exercise
Supervisor: Dr. Cameron Mitchell
Committee member: Dr. Robert Bouschel, Dr. Bill Sheel
Abstract:
There are important physiological differences between aerobic exercise (ex: running, cycling) and resistance exercise (ex: weightlifting). During aerobic exercise, the amount of work that can be performed (i.e. work capacity) is dependent upon how quickly active muscle can generate usable energy for contraction using the oxygen delivered from the blood. In resistance exercise, work capacity is dependent on the external load, which requires different levels of muscle contractile force to move. When working against a heavy external resistance, the active muscles can contract so strongly that blood flow, and therefore oxygen delivery to the active muscle, is blocked. This blockage of blood flow and oxygen delivery severely limits work capacity. In addition, central and peripheral fatigue both contribute to determining work capacity. There has been little research conducted to determine how oxygen kinetics and mechanisms of fatigue affect work capacity in multi-joint resistance exercises such as back squats. Therefore, the purpose of this research is to determine how oxygen delivery/utilization and central/peripheral fatigue affect work capacity at low and high relative loads during multi-joint resistance exercise. Thirty healthy participants will perform maximum repetitions against four varying loads (35, 50, 65 and 80% of individual one-repetition maximums). Participants will be sorted based on training status: endurance-trained, resistance-trained, and untrained. Muscle oxygen delivery and utilization will be measured via pulmonary gas exchange and near-infrared spectroscopy, respectively. Blood lactate and quadriceps force loss post-exercise will clarify whether central or peripheral factors limit performance.