The physiology group primarily seeks to further the fundamental understanding of the cardiovascular and respiratory determinants of human exercise performance. This includes, the factors regulating skeletal muscle blood flow and cardiac function during exercise, as well as the respiratory-related limitations to exercise tolerance. The role of environmental stressors, such as heat and hypoxia, is also a particular focus of our work.

Cardiovascular Physiology

Cardiovascular strain can limit exercise performance in human beings by reducing oxygen supply and thereby impairing tissue oxygen availability and aerobic metabolism. Our research has provided strong support for this idea by establishing that fatigue during intense whole body exercise is preceded by reductions in cardiac output and concurrent declines in blood flow and oxygen supply to exercising skeletal muscle and brain. This phenomenon is closely associated with limitations in stroke volume and increases in sympathetic vasoconstrictor nerve activity to the peripheral vasculature (see Fig. 1; click figures to enlarge). Importantly, our experimental observations also indicate that the consequences of reductions in oxygen supply on aerobic metabolism are greater in exercising muscles compared to the human brain because of the much smaller functional oxygen extraction reserve in contracting muscles. 

Our group has also made important contributions to the understanding of the role of the red blood cell and intravascular adenosine triphosphate (ATP) in the regulation of the local processes that match the supply of oxygen and blood to increases in metabolic and thermoregulatory demands in skeletal muscles in conditions of submaximal exercise, hypoxia, heat stress and dehydration (see Fig. 2). 

A recent discovery is that 1) elevated temperature is a potent physiological stimulus for ATP release from human red blood cells, and 2) elevations in limb blood flow in humans exposed to isolated limb heating or performing exercise in heat stress conditions are closely associated with increases in local temperature and plasma ATP concentration. This discovery opens the opportunity for using local heating as either a therapeutic means of elevating limb tissue blood flow in humans with impaired peripheral circulation or an ergogenic means for athletes who might benefit from elevated limb tissue blood flow and temperature at onset of sprinting events.

Fig. 1 Cardiovascular Determinants of Exercise Performance

Fig. 2 Mechanisms of Erythrocyte Control of Oxygen Delivery

Physiology of Human Performance

IOC Consensus Statement

Red Cells and Flow Control

Respiratory Physiology

Respiratory limitations to exercise tolerance can arise from diseases such as asthma, but also from mechanical constraints imposed by the respiratory pump musculature. We are best known for our research in respiratory muscle fatigue/training, an area where our group has been at the vanguard of, 1) describing fatigue and responses to training of the respiratory muscles, and 2) providing insights into underlying mechanisms. The latter includes cardiovascular changes triggered by respiratory muscle work, and serves to illustrate the close integration of the respiratory and cardiovascular systems (see Fig. 3).

The group has also made major contributions to the understanding of the central and peripheral components of fatigue during exercise, especially in the presence of arterial hypoxaemia.

Our research on exercise-induced asthma (EIA) is also at the forefront, and extends from describing the prevalence of EIA in elite athletes, to understanding the pathophysiological mechanisms. In the applied context, we offer services to athletes with breathing-related problems (eg exercise-induced asthma screening), as well as those seeking to minimise respiratory limitations to their performance.

Fig. 3 Mechanisms by which Inspiratory Muscle Training Improves Exercise Performance

Guide to Breathing Training for Sport

Guide to Respiratory Muscle Training for Clinicians

CSMHP - Home | Biomechanics | Physiology | Psychology