Transfer of momentum from different arm segments to a light movable target during a straight punch thrown by expert boxers |
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| Authors: | N C Spurway B Ekblom T D Noakes P D Wagner |
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| Institution: | 1. College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow , UK neil.spurway@glasgow.ac.uk;3. Department of Physiology and Pharmacology , Karolinska Institute , Stockholm , Sweden;4. Swedish School of Sport and Health Sciences , Stockholm , Sweden;5. Department of Human Biology and Sports Science Institute of South Africa , University of Cape Town , Newlands , South Africa;6. Department of Medicine , University of California San Diego , San Diego , California , USA |
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| Abstract: | Abstract Three modern views about the factors limiting oxygen uptake in healthy humans are set against the original (early 1920s) concept of A. V. Hill and colleagues. The majority view for most of the intervening time has been that cardiac output is the essential limiting function. Among recent research in support of this contention is that, in quadrupeds, pericardiectomy, which allows greater diastolic filling, elevates maximum oxygen uptake; however, the relevance to bipedal exercise can be questioned. In any case, algebraic analyses of model systems indicate that all identifiable stages on the oxygen transport pathway, from pulmonary diffusion to oxidative phosphorylation in skeletal muscle mitochondria, materially influence maximum uptake. Thus, if a high cardiac output is to be of benefit, all the other steps must function better too. Nevertheless, these two viewpoints concur that the limit to maximum oxygen uptake is somatic. In contrast, there are strong indications that at altitudes where oxygen availability is about half that at sea level, cerebral oxygenation is a limiting factor, and some recent experiments raise the possibility that it might be a substantial influence at sea level also. Clearly, consensus cannot yet be reached on the question posed in the title. |
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| Keywords: | Cardiac output gas exchange pulmonary oxygenation cerebral oxygenation muscle oxygen uptake maximum perfusion muscle |
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