title: Substrate oxidation during exercise at moderate and hard intensity in middle-aged and young athletes vs sedentary men.
abstract: 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.
authors.affiliation: Metabolic Unit, Service Central de Physiologie Clinique, Centre d'Exploration et de Réadaptation des Anomalies Métaboliques et Musculaires (CERAMM), 34295 Montpellier Cedex 5, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Manetta
authors.forename: Jean-Frédéric
authors.initials: JF
authors.lastname: Brun
authors.forename: Christian
authors.initials: C
authors.lastname: Prefaut
authors.forename: Jacques
authors.initials: J
authors.lastname: Mercier
mesh_terms: D000328:Adult; D000367:Age Factors; D001786:Blood Glucose; D002153:Calorimetry, Indirect; D004837:Epinephrine / Q000097:blood; D005080:Exercise Test; D006801:Humans; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology; D013177:Sports
chemical_list: D001786:Blood Glucose; D007328:Insulin; D019344:Lactic Acid; D009638:Norepinephrine; D004837:Epinephrine