Acute respiratory muscle unloading improves time-to-exhaustion during moderate- and heavy-intensity cycling in obese adolescent males

Abstract

Obesity significantly impairs breathing during exercise. The aim was to determine, in male obese adolescents (OB), the effects of acute respiratory muscle unloading, obtained by switching the inspired gas from ambient air (AIR) to a normoxic helium + oxygen gas mixture (HeO2) (AIR → HeO2) during moderate [below gas exchange threshold (GET)] and heavy [above GET] constant work rate cycling. Ten OB [age 16.0 ± 2.0 years (mean ± SD); body mass index (BMI) 38.9 ± 6.1 kg/m2] and ten normal-weight age-matched controls (CTRL) inspired AIR for the entire exercise task, or underwent AIR → HeO2 when they were approaching volitional exhaustion. In OB time to exhaustion (TTE) significantly increased in AIR → HeO2 vs. AIR during moderate [1524 ± 480 s vs. 1308 ± 408 (P = 0.024)] and during heavy [570 ± 306 s vs. 408 ± 150 (P = 0.0154)] exercise. During moderate exercise all CTRL completed the 40-min task. During heavy exercise no significant differences were observed in CTRL for TTE (582 ± 348 s [AIR → HeO2] vs. 588 ± 252 [AIR]). In OB, but not in CTRL, acute unloading of respiratory muscles increased TTE during both moderate- and heavy-exercise. In OB, but not in CTRL, respiratory factors limit exercise tolerance during both moderate and heavy exercise.

Energy cost of walking and body composition changes during a 9-month multidisciplinary weight reduction program and 4-month follow-up in adolescents with obesity

“…Therefore, previous studies showed that a 12-week diet and physical activity program, induced BM loss and reduction of trunk FM, which significantly enhanced breathing mechanics in men and women with obesity (Babb et al 2011;Bhammar et al 2016). Moreover, it was shown (Alemayehu et al 2020;Salvadego et al 2017) that a decrease in Cw was associated with a reduction of V'O 2 of respiratory muscles after 3 weeks of training of respiratory muscles, or acute respiratory muscle unloading. Potential mechanisms underlying the decrease of O 2 cost of breathing in adolescents with obesity are partially described by decreased FM and load on the trunk region (Babb et al 2011;Milic-Emili et al 2007), augmented efficiency of respiratory muscles thanks to an increase in both chest wall and compliance and lung compliance (Babb et al 2011;Pelosi et al), and decreased airway resistance (Babb et al 2011).…”