Oxygen uptake kinetics during severe exercise: a comparison between young and older men
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This study examined the relationship between the slow component of oxygen uptake kinetics and muscle electromyography (EMG) during severe exercise in nine young (21.7ᰮ9 yr) and nine older (71.6ᰮ8 yr) men. Oxygen uptake and surface EMG activity of the left vastus lateralis muscle were measured during a 7-min square-wave bout of severe exercise on a cycle ergometer. The absolute amplitude of the oxygen uptake slow component was greater and occurred 60 s earlier in the young compared to older subjects. However, the rate of increase in the slow component, expressed as a percentage of the total oxygen uptake response per unit time, was not different between young and older subjects (young: 4.8ᰮ5% 砭in-1; older: 4.9ᰮ6% 砭in-1). The mean power frequency (MPF) of the EMG increased significantly during the slow component phase of exercise by 6.4ᱮ0% in the young and by 5.4ᰮ7% in the older group and this rise was not significantly different between the two groups. These results indicate that normal ageing may not alter the oxygen uptake slow component (measured as the rate of increase in oxygen uptake) and that this finding may be related to similar muscle fibre recruitment patterns in the two groups during severe-intensity exercise.
Respiratory Physiology and Neurobiology