Obese adolescents (OB) have an increased O2 cost of exercise, attributable in part to an increased O2 cost of breathing. In a previous work a short (3-week) program of respiratory muscle endurance training (RMET) slightly reduced in OB the O2 cost of high-intensity cycling and improved exercise tolerance. We hypothesized that during treadmill walking the effects of RMET would be more pronounced than those observed during cycling. Sixteen OB (age 16.0 +/- 0.8 years; body mass (BM) 127.7 +/- 14.2 kg; body mass index 40.7 +/- 4.0 kg/m2) underwent to 3-week RMET (n = 8) superimposed to a multidisciplinary BM reduction program, or (CTRL, n = 8) only to the latter. Heart rate (HR) and pulmonary O2 uptake (VO2) were measured during incremental exercise and 12-min constant work rate (CWR) walking at 60% (moderate-intensity, MOD) and 120% (heavy-intensity, HEAVY) of the gas exchange threshold (GET). The O2 cost of walking (aerobic energy expenditure per unit of covered distance) was calculated as VO2/velocity. BM decreased (approximately 4 to 5 kg) both in CTRL and in RMET. VO2peak and GET were not affected by both interventions; the time to exhaustion increased following RMET. During MOD and HEAVY RMET decreased VO2, the O2 cost of walking (MOD 0.130 +/- 0.033 mL/kg/m (before) versus 0.109 +/- 0.027 (after), p = 0.03; HEAVY: 0.196 +/- 0.031 (before) versus 0.180 +/- 0.025 (after), p = 0.02), HR and rates of perceived exertion; no significant changes were observed in CTRL. In OB a short RMET program lowered the O2 cost of MOD and HEAVY walking and improved exercise tolerance. RMET could represent a useful adjunct in the control of obesity.

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