The influence of breathing mechanics on the development of the slow component of O2 uptake

Respiratory Muscle Interval Training Improves Exercise Capacity in Obese Adolescents during a 3-Week In-Hospital Multidisciplinary Body Weight Reduction Program

The purpose of this study was to determine whether a novel approach of interval training targeted to the respiratory muscles (RMIT; normocapnic hyperpnea with resistance) in addition to a multidisciplinary in-hospital body weight reduction program (BWRP) was able to improve the integrative response to exercise in young patients with obesity. Nine male patients (17.9 ± 4.9 (x ± SD) years; 113.8 ± 16.3 kg) underwent 12 sessions of RMIT and eight age-and sex-matched patients underwent 12 sessions of a sham protocol (CTRL) during the same 3-week BWRP. Before and after the interventions the patients performed an incremental and a heavy-intensity constant work-rate (CWR>GET) cycling exercise to voluntary exhaustion. Body mass decreased by ~4.0 kg after both RMIT (p = 0.0001) and CTRL (p = 0.0002). Peak pulmonary O₂ uptake (V˙O₂) increased after RMIT (p = 0.02) and CTRL (p = 0.0007). During CWR>GET at ISO-time, V˙O₂ (p = 0.0007), pulmonary ventilation (p = 0.01), heart rate (p = 0.02), perceived respiratory discomfort (RPE_R; p = 0.03) and leg effort (p = 0.0003) decreased after RMIT; only RPE_R (p = 0.03) decreased after CTRL. Time to exhaustion increased after RMIT (p = 0.0003) but not after CTRL. In young patients with obesity, RMIT inserted in a 3-week BWRP reduced the cardiorespiratory burden, the metabolic cost, the perceived effort, and improved exercise tolerance during heavy-intensity cycling.

Respiratory muscle endurance training reduces the O2 cost of cycling and perceived exertion in obese adolescents

In obesity, the increased O2 cost of breathing negatively affects the O2 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 O2 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 O2 uptake (V̇o2), heart rate (HR), and ratings of perceived exertion for dyspnea/respiratory discomfort (RPER) and leg effort (RPEL) were determined. Body mass decreased (by ~3.0 kg) after both RMET ( P = 0.003) and CTRL ( P = 0.002). Peak V̇o2 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 O2 cost of cycling at the end of exercise ( P = 0.02), the slope of V̇o2 vs. time (3–12 min) ( P = 0.01), RPER ( P = 0.01), and RPEL ( 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 O2 cost of cycling and perceived exertion during constant heavy-intensity exercise.

Respiratory and locomotor muscle implications on the VO2 slow component and the VO2 excess in young trained cyclists

We investigated the impact of ramp and constant-load exercise on (i) respiratory muscle fatigue and locomotor muscle oxygenation, (ii) their relationship with the excess VO₂ and VO₂ slow component (SC). Fourteen male cyclists performed two tests to exhaustion: an incremental ramp and a constant-load exercise with continuous monitoring of expired gases and oxygenation of the vastus lateralis muscle on two separate days. Maximal inspiratory (MIP) and expiratory (MEP) pressure measurements were taken at rest and post- exercise. The VO₂ excess represents the difference between VO_2max observed and VO_2max expected using linear equation between the VO₂ and the intensity before gas-exchange threshold. During the ramp exercise, MIP and MEP declined by 13±8 and 19±10%, respectively (p<0.05). MIP and MEP were not correlated to the excess VO₂ (0.09±0.05lmin^-1). During the constant-load exercise, the VO₂ SC (0.70±0.22lmin^-1) was correlated (r=0.68, p<0.01) to deoxyhemoglobin SC (2.94±1.25AU) but not to the excess VO₂ (r=0.30, p=0.2). Additionally, the significant decrease in MIP (20±9%) and MEP (23±11%) was correlated (r=0.55, p<0.05 and r=0.75, p<0.05, respectively) to the VO₂ SC. Our results show that respiratory muscle fatigue was correlated to the VO₂ SC in the constant-load exercise, whereas it was not correlated to the excess VO₂ in ramp exercise may be because of our small excess VO₂.

Acute respiratory muscle unloading by normoxic helium-O₂ breathing reduces the O₂ cost of cycling and perceived exertion in obese adolescents

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) and 120 % 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, and 2.23 ± 0.31 vs. 2.54 ± 0.27 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) and ~15 % (>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.

Evidence of break-points in breathing pattern at the gas-exchange thresholds during incremental cycling in young, healthy subjects

The present study investigated whether 'break-points' in breathing pattern correspond to the first ([Formula: see text]) and second gas-exchange thresholds ([Formula: see text]) during incremental cycling. We used polynomial spline smoothing to detect accelerations and decelerations in pulmonary gas-exchange data, which provided an objective means of 'break-point' detection without assumption of the number and shape of said 'break-points'. Twenty-eight recreational cyclists completed the study, with five individuals excluded from analyses due to low signal-to-noise ratios and/or high risk of 'pseudo-threshold' detection. In the remaining participants (n = 23), two separate and distinct accelerations in respiratory frequency (f (R)) during incremental work were observed, both of which demonstrated trivial biases and reasonably small ±95% limits of agreement (LOA) for the [Formula: see text] (0.2 ± 3.0 ml O(2) kg(-1) min(-1)) and [Formula: see text] (0.0 ± 2.4 ml O(2) kg(-1) min(-1)), respectively. A plateau in tidal volume (V (T)) data near the [Formula: see text] was identified in only 14 individuals, and yielded the most unsatisfactory mean bias ±LOA of all comparisons made (-0.4 ± 5.3 ml O(2) kg(-1) min(-1)). Conversely, 18 individuals displayed V (T)-plateau in close proximity to the [Formula: see text] evidenced by a mean bias ± LOA of 0.1 ± 3.1 ml O(2) kg(-1) min(-1). Our findings suggest that both accelerations in f (R) correspond to the gas-exchange thresholds, and a plateau (or decline) in V (T) at the [Formula: see text] is a common (but not universal) feature of the breathing pattern response to incremental cycling.