Cardiac, respiratory and vascular aspects of performance

This issue of Experimental Physiology contains symposium papers from the conference The Biomedical Basis of Elite Performance held on the 19–21 March 2012 at The Queen Elizabeth II Conference Centre, London which covers the theme of Cardiac, respiratory and vascular aspects of performance. In the first of these, Green et al. (2012) asks the question, if there is an athletes heart, is there an athlete’s artery? They make a compelling case for training-induced remodelling of the vasculature at the conduit and resistance artery level in athletes. These adaptations are necessary to cope with the substantial cardiac output seen during heavy exercise and explain the well-known observation that, even with their exceptional cardiac output, athletes do not experience abnormally raised arterial blood pressure during maximal exercise. Green et al. (2012) also point to findings from the study of athletes as well as laboratory-based training studies on ‘lesser mortals’ that have led to better understanding of vascular adaptations to exercise. These have important implications for the health of the general populace. They speculate that intravascular laminar shear stress may be the key factor in causing the vascular adaptations they describe. As this is increased by exercise and experienced by the whole conduit and resistance artery network, there is potential for system-wide beneficial adaptation to exercise, not only in the vessels supplying the exercising muscle. DeVan & Seals (2012) extend the theme of vascular adaptation to exercise with their review of ‘vascular health in the ageing athlete’. As population statistics indicate a rapid worldwide increase in the number of older people, the topic is very timely. They explain that master athletes who perform endurance training-based activities demonstrate a more favourable arterial function–structure phenotype, including lower large elastic artery stiffness, enhanced vascular endothelial function and less arterial wall hypertrophy. Mechanisms behind these adaptations are still uncertain, but once again shear stress is a strong candidate. This combination of vascular traits is associated with a lower risk of clinical cardiovascular disease in endurance-trained master athletes. As such, DeVan & Seals (2012) suggest that this group may represent an exemplary model of healthy or ‘successful’ vascular ageing. In contrast, master athletes engaging in resistance-type exercise do not show this beneficial profile; indeed, they may exhibit less favourable arterial function–structure than their endurance-trained peers and, in some instances, untrained adults. These findings have obvious implications for ‘best advice’ to be given to those striving to reduce risk factors for cardiovascular disease in old age. Next, Amann (2012) shifts our attention to ‘pulmonary system limitations to endurance exercise performance in humans’. He emphasizes three respiratory system-related mechanisms which may limit performance by impairing oxygen transport to the locomotor musculature. In fact, two of these mechanisms operate by compromising cardiovascular system responses to exercise, which clearly illustrates the need for an integrative approach to the study of human exercise physiology. The first limitation to performance may be caused by a restriction of stroke volume and cardiac output during exercise, due to excessive intrathoracic pressure fluctuations during breathing. A second mechanism is reflex limb muscle vasoconstriction that is triggered by thin fibre muscle afferent activation in response to fatiguing respiratory muscle work. Both mechanisms can therefore compromise locomotor muscle blood flow. The third mechanism relates to the fact that in some endurance-trained athletes, and perhaps more commonly in female athletes, there is a susceptibility to arterial desaturation during exercise and, rather surprisingly, in some individuals this occurs at submaximal exercise intensities. The finding that this arterial