Date of Award
2006
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Kinesiology
Supervisor
Dr. Greg Marsh
Abstract
This thesis examined the effects of an altered blood and intracellular acid-base status on skeletal muscle energetics during exercise. Phosphorus-31 magnetic resonance spectroscopy and near infrared spectroscopy were utilized to examine the dynamics of high-energy phosphates in skeletal muscle and O2 in the surrounding microvasculature during constant-load exercise in healthy young adults. Acid-base status was manipulated by NaHCO3 ingestion, hyperventilation-induced hypocapnia, and prior exercise. NaHCO3 ingestion reduced the accumulation of intracellular hydrogen ion concentration ([H*]) and decreased phosphocreatine (PCr) breakdown during the later stages of heavy-intensity forearm exercise. Furthermore, the findings indicated that a reduced ADP (or related) signal is required to drive oxidative phosphorylation in less acidic conditions. On the other hand, hyperventilation-induced hypocapnia increased PCr breakdown and slowed the time course of adaptation of the PCr kinetic response during moderate-intensity plantar flexion exercise. These findings were consistent with hyperventilation slowing the kinetics of muscle O2 consumption. An induced acidosis at exercise onset (by prior heavy-intensity exercise) lowered [ADP] during the early stages of exercise. However, the ATP supply from oxidative phosphorylation did not appear to be reduced, suggesting that other factors that drive oxidative phosphorylation must have been enhanced (e.g., NADH availability, O2 delivery). Collectively, the findings of this thesis indicate that acid-base status plays an important role in modulating skeletal muscle energetics during exercise in human subjects.
Recommended Citation
Forbes, Sean Charles, "Effects of Acid-base Status on Skeletal Muscle Energetics during Exercise" (2006). Digitized Theses. 5061.
https://ir.lib.uwo.ca/digitizedtheses/5061