Exercise physiology and human performance: systems biology before systems biology!

In this edition of The Journal of Physiology we focus on issues related to how humans (and animals) meet the acute physiological demands of exercise and also on the factors that govern some of the long-terms adaptations to physical activity and exercise training. The fact that 2008 is an Olympic year was a stimulus for this general topic. Additionally, some of the most cited papers in the history of The Journal of Physiology have direct relevance to exercise, and many questions first raised over 100 years ago remain both unanswered and relevant today. Finally, the scientific basis of human performance and studies of how both athletes and ‘normal’ subjects respond to exercise is of interest to the general public and public policy makers. In this context, the field of ‘exercise’ is enormous and touches on every conceivable organ system and every level of biological organization. Thus, reviews in all of the key areas were not sought. Instead we sought to focus on areas with direct relevance to human athletic performance (fatigue, , world records, thermoregulation and ageing) and several newer or underappreciated areas (neural adaptations, genetics and evolution, and connective tissue). Since ‘fatigue’ is a key feature of athletic performance, this topic is reviewed by Enoka & Duchateau (2008). is covered by Levine (2008) in the context of what limits and also the continued relevance (or irrelevance) of this measure as an index of ‘maximal’ capacity. What world records and elite endurance performance tell us about integrative physiology is covered by Joyner & Coyle (2008). Since the Summer Olympic games are frequently associated with warm weather Gonzalez-Alonso et al. (2008) discuss how thermoregulation and dehydration can affect performance. Tanaka & Seals (2008) cover issues related to ageing and performance and especially what the older athlete tells us about successful physiological ageing. In an effort to expand beyond the ‘traditional’ areas of ‘exercise physiology’ we asked Nielsen & Cohen (2008) to discuss the neural adaptations to exercise and how the brain and spinal cord adapt to facilitate skill acquisition with practice. Magnusson et al. (2008) also present new ideas on connective tissues showing that in a variety of settings these tissues are far more dynamic than generally appreciated. Finally, much of exercise is about oxygen transport and Koch & Britton (2008) consider this question at levels of integration ranging from geophysics to evolution to disease. One general conclusion from all of the reviews and papers is that the main regulatory and adaptive responses to acute and chronic exercise defy simple reductionist explanations. A more provocative conclusion is that before the reductionist community naively concluded they needed to reinvent and rename physiology in the guise of ‘systems biology’, investigators interested in exercise were already committed to understanding the interactions of key biological responses at multiple levels of organization and integration. An even more provocative conclusion is that the systems biologists have much to learn from the successes of investigators interested in exercise and even more to learn from their continuing questions.