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Metabolism. 2005 Nov;54(11):1411-9.

Substrate oxidation during exercise at moderate and hard intensity in middle-aged and young athletes vs sedentary men.

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Metabolic Unit, Service Central de Physiologie Clinique, Centre d'Exploration et de Réadaptation des Anomalies Métaboliques et Musculaires (CERAMM), 34295 Montpellier Cedex 5, France.


This study investigated the combined effects of endurance training and aging on substrate oxidation during exercise. Thirty-one healthy male subjects in 4 groups (8 middle-aged trained cyclists, 8 young trained cyclists, 7 middle-aged sedentary men, and 8 young sedentary men) performed 2 50-minute cycle ergometer exercise tests, below and above (+/-15%) their individual ventilatory threshold (VT). Substrate oxidation was evaluated by indirect calorimetry during the steady-state tests. Aging decreased carbohydrate (CHO) use (P<.05) in all subjects regardless of fitness status or exercise intensity. However, it declined 2-fold less in the trained men (P<.05) and was associated with a stronger epinephrine response (P<.05). During hard-intensity exercise, endurance training increased by 100% CHO use in the older men (P<.05). In the younger men, training increased fat oxidation but did not change CHO oxidation, resulting in a marked decrease in the ratio between CHO and fat used at high-intensity exercise (-93%; P<.05). These data suggest an age-related decline in the use of CHO as an energy source in exercising men, independent of intensity level. This decline, however, is attenuated in well-trained men for exercise intensities above the VT. In view of these findings, we hypothesize that cycling training performed at a specific exercise intensity (ie, 15% above VT) may improve CHO mobilization and use in middle-aged men.

[Indexed for MEDLINE]

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