Oxygen uptake kinetics during severe exercise: a comparison between young and older men

This study examined the relationship between the slow component of oxygen uptake ((V)over dot(O 2)) kinetics and muscle electromyography (EMG) during severe exercise in nine young (21.7+/-10.9 yr) and nine older (71.6+/-0.8 yr) men. Oxygen uptake ((V)over dot(O 2)) 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 (V)over dot(O 2) slow component was greater and occurred similar to60 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 (V)over dot(O 2) response per unit time, was not different between young and older subjects (young: 4.8+/-0.5%.min(-1); older: 4.9+/-10.6%.min(-1)). The mean power frequency (MPF) of the EMG increased significantly during the slow component phase of exercise by 6.4+/-1.0% in the young and by 5.4+/-0.7% 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 (V)over dot(O 2) slow component (measured as the rate of increase in (V)over dot(O 2)) and that this finding may be related to similar muscle fibre recruitment patterns in the two groups during severe-intensity exercise. (C) 2003 Elsevier B.V. All rights reserved.