Search

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 (HeO 2 ) (AIR → HeO 2 ) 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/m 2 ] and ten normal-weight age-matched controls (CTRL) inspired AIR for the entire exercise task, or underwent AIR → HeO 2 when they were approaching volitional exhaustion. In OB time to exhaustion (TTE) significantly increased in AIR → HeO 2 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 → HeO 2 ] 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.

Obese adolescents (OB) have an increased O 2 cost of exercise, attributable in part to an increased O 2 cost of breathing. In a previous work a short (3-week) program of respiratory muscle endurance training (RMET) slightly reduced in OB the O 2 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/m 2 ) 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 O 2 uptake ( V ˙ O 2 ) 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 O 2 cost of walking (aerobic energy expenditure per unit of covered distance) was calculated as V ˙ O 2 /velocity. BM decreased (~4-5 kg) both in CTRL and in RMET. V ˙ O 2 peak and GET were not affected by both interventions; the time to exhaustion increased following RMET. During MOD and HEAVY RMET decreased V ˙ O 2, the O 2 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 O 2 cost of MOD and HEAVY walking and improved exercise tolerance. RMET could represent a useful adjunct in the control of obesity., (© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

In obesity, the increased O 2 cost of breathing negatively affects the O 2 cost of exercise and exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, the addition of respiratory muscle endurance training (RMET) (isocapnic hyperpnea) to a standard body mass reduction program decreases the O 2 cost of exercise and perceived exertion. Nine male obese adolescents [16.0 ± 1.4 yr ( x ± SD), body mass 114.4 ± 22.3 kg] underwent 3 wk of RMET (5 days/week) in addition to a standard body mass reduction program. Eight age- and sex-matched obese adolescents underwent only the standard program (CTRL). Before and after interventions, patients performed on a cycle ergometer: incremental exercise; 12-min exercises at a constant work rate (CWR) of 65% and 120% at the gas exchange threshold (GET) determined before the intervention. Breath-by-breath pulmonary ventilation (V̇e) and O 2 uptake (V̇o 2 ), heart rate (HR), and ratings of perceived exertion for dyspnea/respiratory discomfort (RPE R ) and leg effort (RPE L ) were determined. Body mass decreased (by ~3.0 kg) after both RMET ( P = 0.003) and CTRL ( P = 0.002). Peak V̇o 2 was not affected by both interventions. Peak work rate was slightly, but significantly ( P = 0.04), greater after RMET but not after CTRL. During CWR < GET, no changes were observed after both interventions. During CWR > GET, the O 2 cost of cycling at the end of exercise ( P = 0.02), the slope of V̇o 2 vs. time (3-12 min) ( P = 0.01), RPE R ( P = 0.01), and RPE L ( P = 0.01) decreased following RMET, but not following CTRL. HR decreased after both RMET ( P = 0.02) and CTRL ( P = 0.03), whereas V̇e did not change. In obese adolescents RMET, superimposed on a standard body mass reduction program, lowered the O 2 cost of cycling and perceived exertion during constant heavy-intensity exercise., (Copyright © 2017 the American Physiological Society.)

Purpose: In obesity, an increased work of breathing contributes to a higher O2 cost of exercise and negatively affects exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, acute respiratory muscle unloading via normoxic helium-O2 breathing reduces the O2 cost of cycling and perceived exertion., Methods: Nine males [age 16.8 ± 1.6 (x ± SD) years, body mass 109.9 ± 15.0 kg] performed on a cycle ergometer, breathing room air (AIR) or a 21 % O2-79 % helium mixture (He-O2): an incremental exercise, for determination of [Formula: see text]O2 peak and gas exchange threshold (GET); 12 min constant work rate (CWR) exercises at 70 % of GET (GET) determined in AIR., Results: [Formula: see text]O2 peak was not different in the two conditions. From the 3rd to the 12th minute of exercise (both during CWR < GET and CWR > GET), [Formula: see text]O2 was lower in He-O2 vs. AIR (end-exercise values: 1.40 ± 0.14 vs. 1.57 ± 0.22 L min(-1) GET). During CWR > GET in AIR, [Formula: see text]O2 linearly increased from the 3rd to the 12th minute of exercise, whereas no substantial increase was observed in He-O2. The O2 cost of cycling was ~10 % (GET) lower in He-O2 vs. AIR. Heart rate and ratings of perceived exertion for dyspnea/respiratory discomfort and leg effort were lower in He-O2., Conclusions: In obese adolescents, acute respiratory muscle unloading via He-O2 breathing lowered the O2 cost of cycling and perceived exertion during submaximal moderate- and heavy-intensity exercise.

Repetition of voluntary exercise bouts and of different pharmacological GH-releasing stimuli at 2-h intervals is associated with a complete abolishment of GH responsiveness. By contrast, a different pattern is observed after repeated neuromuscular electrostimulation, which is characterized by preservation of GH responsiveness. Aim of the study was to evaluate GH responses to repeated bouts of respiratory muscle endurance training (RMET) by mean of a specific commercially available device (Spiro Tiger®). Eight healthy men underwent an incremental progressive RMET protocol of 11 daily sessions. Blood samplings for GH, cortisol and lactate (LA) determinations were collected during the 12th session, which was composed of two consecutive bouts of RMET (of identical intensity and duration: 1 min at a respiration rate of 28 acts/min, 5 min at 32 acts/min, 5 min at 34 acts/min, 4 min at 36 acts/min) at a 2 h interval. Baseline GH levels (mean: 0.9±0.4 ng/ml) significantly (p<0.01) increased after the first bout of RMET (peak: 15.7±4.0 ng/ml). The administration of the second bout of RMET resulted in a significantly lower (p<0.05) GH increase (peak: 3.9±0.8 ng/ml) in comparison with the first one. Baseline LA levels (mean: 1.2±0.1 mmol/l) significantly increased (p<0.001) after the first bout of RMET (peak: 2.3±0.2 mmol/l). The administration of the second RMET bout resulted in a comparable LA increase (from a basal value of 1.2±0.1 mmol/l up to a peak of 2.0±0.1 mmol/l, p<0.001). The first bout of RMET caused a significant increase of cortisol levels (p<0.01), starting from a basal mean value of 142.9±9.4 ng/ml up to a peak of 188.8±10.3 ng/ml. By contrast, the second bout of RMET did not induce any significant change of cortisol levels (basal: 149.1±9.0 ng/ml, peak: 168.5±5.1 ng/ml). In conclusion, a single bout of RMET is capable of stimulating GH and cortisol secretions and LA production. When a second bout is repeated after 2 h, there is a blunting of GH and cortisol responses with a preservation of LA release. Further studies are needed to schedule long-term RMET protocols capable of persistently stimulating GH-IGF-I release and to maximally enhance the ergogenic and metabolic benefits of this intervention either in normal subjects (e.g. athletes) or patients with an impairment of motor capabilities requested to perform normal daily activities (i.e. severely obese and elderly people).

Several studies have demonstrated that the obesity-related hyposomatropism is usually reversible after a consistent weight loss induced by diet and/or bariatric surgery. Recently, a single bout of respiratory muscle endurance training (RMET) by means of a specific commercially available device (Spiro Tiger ® ) has been reported to induce a marked GH response in obese adults, its GH-releasing effect being significantly lower in obese adolescents. The GH response disappeared in both obese adults and adolescents when RMET was repeated at 2-h intervals inbetween. The aim of the present study was to evaluate GH responses to repeated bouts of RMET administered before and after a 3-week in-hospital multidisciplinary body weight reduction program (entailing energy-restricted diet, 90 min/daily aerobic physical activity, psychological counseling, and nutritional education) combined with a progressively increasing RMET (15 daily sessions, 5 sessions per week) in 7 obese male adolescents [age: 12-17 years; body mass index (BMI): 38.5 ± 3.1 kg/m 2 ; percent fat mass (FM): 37.0 ± 2.0 %]. Blood samplings for GH determinations were collected during the 1 st and 15 th sessions, which were composed of 2 consecutive bouts of RMET (of identical intensity and duration) at 2-h interval in-between. At the beginning of the study, baseline GH levels significantly increased after the first bout of RMET in all subjects (p < 0.05). The administration of the second bout of RMET resulted in a significantly lower (p < 0.05) GH increase in comparison with the first one. Three weeks of the integrated intervention significantly reduced both body weight (from 115.3 ± 9.2 kg to 111.5 ± 8.7 kg, p < 0.05) and FM (from 43.1 ± 5.7 kg to 41.9 ± 5.3 kg, p < 0.05), these combined effects being, however, not sufficient to influence GH responsiveness to the 2 repeated bouts of RMET (GH peaks to the first bout: 4.8 ± 1.6 ng/ml vs. 4.8 ± 1.6 ng/ml; GH peaks to the second bout: 0.9 ± 0.2 ng/ml vs. 1.1 ± 0.1 ng/ ml, before and after 3 weeks of the treatment, respectively, p = NS). In conclusion, a 3-week incremental RMET combined with a body weight reduction intervention does not seem useful to positively influence the reduced GH responsiveness to 2 repeated RMET bouts in obese adolescents. More intensive and/or long-term RMET protocols, associated with energy-restricted diets, determining more consistent changes in body composition, are likely needed to restore the impaired GH-IGF-1 function of obese adolescents. [ABSTRACT FROM AUTHOR]

Repeated bouts of GH-releasing stimuli (both pharmacological and physiological, such as aerobic exercise) at 2-h intervals are associated with a blunting of somatotropic responsiveness in normal adults, while a persistent GH responsiveness to consecutive stimuli is reported to occur in children and adolescents. Recently, a single bout of respiratory muscle endurance training (RMET) by means of a specifi c commercially available device (Spiro Tiger ® ) has been shown to induce relevant GH responses in both normal-weighted and obese adult subjects. The aim of the present study was to evaluate GH responses to repeated bouts of RMET in obese adolescents and adults. Seven obese male adolescents (age: 15.7 ± 0.4 years; body mass index, BMI: 38.0 ± 3.3 kg/m ² ) and 10 obese adults (age: 22.2 ± 1.4 years; BMI: 39.9 ± 1.0 kg/m 2 ) underwent an incremental progressive RMET protocol of 11 daily sessions. Blood samplings for GH determinations were collected during the 12 th session, which was composed of 2 consecutive bouts of RMET (of identical intensity and duration: 1 min at a respiration rate of 28 acts/min, 5 min at 32 acts/min, 5 min at 34 acts/min, 4 min at 36 acts/min) at a 2-h interval in-between. Baseline GH levels significantly increased after the first bout of RMET in all subjects, higher GH peaks being found in obese adults than in obese adolescents (peaks: 14.3 ± 2.1 ng/ml vs. 4.8 ± 1.6 ng/ml, respectively, p < 0.05). The administration of the second bout of RMET resulted in signifi cantly lower (p < 0.05) GH increases in both obese adolescents and obese adults (peaks: 0.9 ± 0.2 ng/ml and 1.6 ± 0.2 ng/ml, respectively) in comparison with the first one. In conclusion, exercise protocols based on repeated bouts of RMET do not seem a valid strategy to persistently stimulate GH-IGF-1 release in obese adolescents, since GH responses to a single bout are actually modest in comparison with those of obese adults and completely abolished after repeated bouts at 2 h interval in-between. [ABSTRACT FROM AUTHOR]

It is well established that obese patients are hypo-responsive to classical GH-releasing stimuli, including aerobic exercise. Recently, we have demonstrated that whole body vibration was able to markedly stimulate GH secretion in obese patients, thus suggesting that this refractoriness is not absolute but dependent on the GH-releasing stimulus. Furthermore, we have shown the ability of a respiratory muscle endurance training (RMET) to stimulate GH and cortisol secretion in healthy subjects. The objective of this study was to evaluate the effects of RMET on GH and cortisol responses in severely obese patients. Eight severely obese patients (4 M/4 F, mean age ± SEM: 22.8 ± 1.6 years, body mass index, BMI: 39.9 ± 1.1 kg/m 2 ) underwent an incremental progressive RMET protocol of 11 daily sessions, obtained through the use of a specifically designed respiratory device (Spiro Tiger ® ). The 12th session of RMET (15 min duration: 1 min at a respiration rate of 28 acts/min, 5 min at 32 acts/ min, 5 min at 34 acts/min, 4 min at 36 acts/min) was associated with blood samplings for determination of GH, cortisol, and lactate (LA) levels. An age- and sex-matched normal-weighted control group (n = 7, 4 M/3 F, age: 26.1 ± 3.1 years, BMI: 22.4 ± 0.6 kg/m 2 ) was also recruited. In both normal-weighted subjects and obese patients, GH secretion significantly increased after a 15-min RMET session. Although serum GH levels at 30 min were higher in normal-weighted subjects than in obese patients, there was no statistically significant difference in either GH peaks or net GH areas under the curve between the 2 groups. RMET significantly increased serum cortisol levels in normal-weighted subjects, but was associated to a progressive cortisol decline in obese patients. RMET stimulated LA production, with no significant differences in normalweighted subjects and in obese patients. A 15-min RMET session was capable to induce a GH response in severely obese patients, which was comparable to that recorded in normalweighted subjects. A progressive decline in serum cortisollevels occurred in obese patients after RMET, while an opposite pattern (i. e., a significant cortisol increase) was found in normalweighted subjects. Optimization of long-term RMET protocols could represent a valid strategy to (physiologically) stimulate GH/IGF-I system in those GH hyposecretory states such as obesity. [ABSTRACT FROM AUTHOR]