This study examined whether increased plasma volume (PV) and albumin content (Albcont) in plasma for 23 h after exercise were attenuated in older subjects compared with in young adult subjects, and if this attenuation abated by supplementation with protein and carbohydrate (CHO) immediately after exercise. Eight moderately active older (∼68 yr) and 8 young (∼21 yr) men performed two trials: control (CNT) and Pro-CHO in which subjects consumed placebo (0.5 kcal, 0 g protein, 0.5 mg Na+ in 3.2 ml total fluid volume/kg body wt) or protein and CHO mixture (3.2 kcal, 0.18 g protein, 0.5 mg Na+ in 3.2 ml total fluid volume/kg body wt) supplementations, respectively, immediately after high-intensity interval exercise for 72 min [8 sets of 4 min at 70-80% peak oxygen consumption rate (V̇O2peak) intermitted by 5 min at 20% V̇O2peak]. PV, Albcont, and plasma globulin content (Glbcont) were measured before exercise, at the end of exercise, every hour from the 1st to the 5th hour after exercise, and at the 23rd hour after exercise. From 12 h before the start to the end of experiment, food intake was controlled to the age-matched recommended dietary allowances. We found that during the first 4 h after exercise in CNT, Alb cont recovered less in the older than the young group by ∼0.04 g/kg (P < 0.05), while it generally recovered more with Pro-CHO than CNT by ∼0.09 and ∼0.04 g/kg in the young and older group, respectively, accompanied by a greater increase in PV by ∼1 and ∼2 ml/kg, respectively, during the 23 h after exercise (P < 0.05). Glbcont remained constant throughout the experiment in both trials for both age groups. Thus the attenuated responses of Albcont and PV after exercise in older subjects were restored by protein and CHO supplementation immediately after exercise, similarly to young subjects.
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