Three weeks of respiratory muscle endurance training improve the O₂ cost of walking and exercise tolerance in obese adolescents

Abstract

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 (trueV˙O2) 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 trueV˙O2/velocity. BM decreased (~4–5 kg) both in CTRL and in RMET. trueV˙O2peak and GET were not affected by both interventions; the time to exhaustion increased following RMET. During MOD and HEAVY RMET decreased trueV˙O2, the O2 cost of walking (MOD: 0.130 ± 0.033 mL/kg/m [before] vs. 0.109 ± 0.027 [after], P = 0.03; HEAVY: 0.196 ± 0.031 [before] vs. 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.

Breathing during exercise: There is no such thing as a free lunch

“…Although the specific mechanistic bases for the findings of Alemayehu et al. () are not necessarily known, they fit with our working hypothesis; namely, that the muscles of respiration have a preferentially important role in the response to exercise. Overall, it should be appreciated that breathing, although normally performed without conscious effort, should not be taken for granted.…”

“…The observations by Alemayehu et al. () are important, because improvements in exercise tolerance in obesity have the potential to be a relevant adjunct intervention in the control of obesity. Additional research should be targeted to gain an understanding of the underlying physiology of their observations and the efficacy of the intervention.…”

“…We read with interest the recent work of Alemayehu et al. (), who had obese male teenagers perform specific training of the respiratory muscles for 3 weeks during a weight‐loss programme. Respiratory muscle training reduced the O 2 cost of breathing during walking and improved exercise tolerance.…”

“…Several research groups have shown that the arms and legs cannot both be perfused maximally during heavy exercise. For example, Calbet et al (2004) showed that maximal blood flow conductance to the arms and legs of well-trained cross-country skiers must be constrained in order to maintain appropriate blood pressure. It is important to recognize that the act of breathing during exercise requires repeated forceful contractions of the respiratory musculature, which impose significant metabolic and blood flow demands.…”

“…It is also known that obesity is associated with altered respiratory mechanics and a higher O 2 cost of breathing, presumably related to fat mass on the chest wall. We read with interest the recent work ofAlemayehu et al (2018), who had obese male teenagers perform specific training of the respiratory muscles for 3 weeks during should not be taken for granted. The respiratory muscles will command their own share of the 'cardiac output pie' , and this impacts the integrative response to exercise.…”