Effects of exercise training on thermoregulatory responses and blood volume in older men

Abstract

We assessed the effects of aerobic and/or resistance training on thermoregulatory responses in older men and analyzed the results in relation to the changes in peak oxygen consumption rate (V˙o 2 peak) and blood volume (BV). Twenty-three older men [age, 64 ± 1 (SE) yr; V˙o 2 peak, 32.7 ± 1.1 ml · kg−1 · min−1] were divided into three training regimens for 18 wk: control (C; n = 7), aerobic training (AT; n = 8), and resistance training (RT; n = 8). Subjects in C were allowed to perform walking of ∼10,000 steps/day, 6–7 days/wk. Subjects in AT exercised on a cycle ergometer at 50–80%V˙o 2 peak for 60 min/day, 3 days/wk, in addition to the walking. Subjects in RT performed a resistance exercise, including knee extension and flexion at 60–80% of one repetition maximum, two to three sets of eight repetitions per day, 3 days/wk, in addition to the walking. After 18 wk of training,V˙o 2 peak increased by 5.2 ± 3.4% in C ( P > 0.07), 20.0 ± 2.5% in AT ( P < 0.0001), and 9.7 ± 5.1% in RT ( P < 0.003), but BV remained unchanged in all trials. In addition, the esophageal temperature (Tes) thresholds for forearm skin vasodilation and sweating, determined during 30-min exercise of 60% V˙o 2 peak at 30°C, decreased in AT ( P < 0.02) and RT ( P< 0.02) but not in C ( P > 0.2). In contrast, the slopes of forearm skin vascular conductance/Tes and sweat rate/Tes remained unchanged in all trials, but both increased in subjects with increased BV irrespective of trials with significant correlations between the changes in the slopes and BV ( P < 0.005 and P < 0.0005, respectively). Thus aerobic and/or resistance training in older men increased V˙o 2 peak and lowered Tes thresholds for forearm skin vasodilation and sweating but did not increase BV. Furthermore, the sensitivity of the increase in skin vasodilation and sweating at a given increase in Tes was more associated with BV than withV˙o 2 peak.