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

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) over dot O-2 (peak)) and blood volume (BV). Twenty-three older men [age, 64 +/- 1 (SE) yr; (V) over dot 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 similar to10,000 steps/day, 6-7 days/wk. Subjects in AT exercised on a cycle ergometer at 50-80% (V) over dot 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) over dot 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 (T-es) thresholds for forearm skin vasodilation and sweating, determined during 30-min exercise of 60% (V) over dot O-2 (peak) at 30degreesC, 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/T-es and sweat rate/T-es 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) over dot O-2 (peak) and lowered T-es 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 T-es was more associated with BV than with (V) over dot O-2 (peak).