A reduction in exercise efficiency with aging limits daily living activities. We examined whether 5-aminolevulinic acid (ALA) with sodium ferrous citrate (SFC) increased exercise efficiency and voluntary achievement of interval walking training (IWT) in older women. Ten women [65 ± 3(SD) yr] who had performed IWT for >12 mo and were currently performing IWT participated in this study. The study was conducted in a placebo-controlled, double-blind crossover design. All subjects underwent two trials for 7 days each in which they performed IWT with ALA+SFC (100 and 115 mg/day, respectively) or placebo supplement intake (CNT), intermittently with a 2-wk washout period. Before and after each trial, subjects underwent a graded cycling test at 27.0°C atmospheric temperature and 50% relative humidity, and oxygen consumption rate, carbon dioxide production rate, and lactate concentration in plasma were measured. Furthermore, for the first 6 days of each trial, exercise intensity for IWT was measured by accelerometry. We found that, in the ALA+SFC trial, oxygen consumption rate and carbon dioxide production rate during graded cycling decreased by 12% (P < 0.001) and 11% (P = 0.001) at every workload, respectively, accompanied by a 16% reduction in lactate concentration in plasma (P < 0.001), although all remained unchanged in the CNT trial (P > 0.2). All of the reductions were significantly greater in the ALA+SFC than the CNT trial (P < 0.05). Furthermore, the training days, impulse, and time at fast walking were 42% (P = 0.028), 102% (P = 0.027), and 69% (P = 0.039) higher during the ALA+SFC than the CNT intake period, respectively. Thus ALA+SFC supplementation augmented exercise efficiency and thereby improved IWT achievement in older women.
We have suggested that a component of skin sympathetic nerve activity (SSNA) synchronized with cardiac cycle might be an active cutaneous vasodilator. However, the possibility that the component involves signals of muscle sympathetic nerve activity (MSNA) was not completely excluded. Since head‐up tilt (HUT) suppresses cutaneous vasodilation in hyperthermia while increases heart rate and arterial pressure, we hypothesized that 30°HUT reduced the SSNA component while enhanced MSNA with reduced right atrial and carotid artery distensions. In 12 men (22–42yr), wearing a perfusion suit, we measured right atrial volume (VRA) and carotid artery diameter (CAD; echocardiography), esophageal temperature (Tes), SSNA and MSNA (microneurography; the peroneal nerve; N=7) during supine and also 30°HUT while Tes was increased by 0.7°C with 47‐°C water perfusion into the suit. We found that HUT reduced the SSNA component (P=0.003) while enhanced MSNA (P=0.007) with reduced right atrial and carotid artery distensions (both P<0.0001). The latency of the SSNA component from R‐wave was 1.0s, shorter than that of MSNA (1.2s; P<0.01). Moreover, the latency of the SSNA component from peak of VRA and that of MSNA from valley of CAD were almost constant, 0.7s and 1.2s, respectively, as reported previously. Thus, we successfully distinguished the SSNA component from MSNA, which might be an active cutaneous vasodilator.
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