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Med Sci Sports Exerc. 2010 Oct;42(10):1891-8. doi: 10.1249/MSS.0b013e3181dd0bba.

Mechanisms for increases in V˙O2max with endurance training in older and young women.

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Canadian Centre for Activity and Aging, University of Western Ontario, London, Ontario, Canada.



To examine the time course and mechanisms of cardiorespiratory fitness adaptation to training in older (O) and young (Y) women.


A total of six O (69 ± 7 yr) and eight Y (25 ± 5 yr) women were examined before training and after 3, 6, 9, and 12 wk of training. Training was performed on a cycle ergometer three times per week for 45 min at ∼70% of V˙O2max.


V˙O2max (mL·kg(-1)·min(-1)) increased within 3 wk, with further changes observed at weeks 6 and 9 in both O (17% ± 14%) and Y and also posttraining (12 wk) in Y (22% ± 6%, P < 0.05). Maximal cardiac output (Q˙max, open-circuit acetylene) and stroke volume increased only in Y after 9 wk of training (P < 0.05). Age × testing time interactions in maximal arterial-venous O2 difference (a-vO2diff) after 6 wk of training revealed a greater dependence on a-vO2diff in O compared with Y (P < 0.05); ∼65% of the change in V˙O2max from pretraining to posttraining was explained by a widened maximal a-vO2diff in O compared with almost equal increases in Q˙max and maximal a-vO2diff in Y. The early adaptations (first 3 wk) in O relied exclusively on a nonsignificant increase in Q˙max, whereas Y depended on a widened maximal a-vO2diff. Later changes in V˙O2max were explained exclusively by an improved maximal a-vO2diff in O and a larger Q˙max in Y.


O and Y women displayed a different time course of training adaptation in V˙O2max, with Y (after an initial improvement in maximal a-vO2diff) depending more on changes in Q˙max and O mostly relying on a widened maximal a-vO2diff.

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