Sex differences in the ventilatory responses to exercise in mild to moderate obesity.

NEW FINDINGS: What is the central question of the study? What are the sex differences in ventilatory responses during exercise in adults with obesity? What is the main finding and its importance? Tidal volume and expiratory flows are lower in females when compared with males at higher levels of ventilation despite small increases in end-expiratory lung volumes. Since dyspnoea on exertion is a frequent complaint, particularly in females with obesity, careful attention should be paid to unpleasant respiratory symptoms and mechanical ventilatory constraints while prescribing exercise. ABSTRACT: Obesity is associated with altered ventilatory responses, which may be exacerbated in females due to the functional consequences of sex-related morphological differences in the respiratory system. This study examined sex differences in ventilatory responses during exercise in adults with obesity. Healthy adults with obesity (n = 73; 48 females) underwent pulmonary function testing, underwater weighing, magnetic resonance imaging (MRI), a graded exercise test to exhaustion, and two constant work rate exercise tests; one at a fixed work rate (60 W for females and 105 W for males) and one at a relative intensity (50% of peak oxygen uptake, V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ ). Metabolic, respiratory and perceptual responses were assessed during exercise. Compared with males, females used a smaller proportion of their ventilatory capacity at peak exercise (69.13 ± 14.49 vs. 77.41 ± 17.06% maximum voluntary ventilation, P = 0.0374). Females also utilized a smaller proportion of their forced vital capacity (FVC) at peak exercise (tidal volume: 48.51 ± 9.29 vs. 54.12 ± 10.43%FVC, P = 0.0218). End-expiratory lung volumes were 2-4% higher in females compared with males during exercise (P < 0.05), while end-inspiratory lung volumes were similar. Since the males were initiating inspiration from a lower lung volume, they experienced greater expiratory flow limitation during exercise. Ratings of perceived breathlessness during exercise were similar between females and males at comparable levels of ventilation. In summary, sex differences in the manifestations of obesity-related mechanical ventilatory constraints were observed. Since dyspnoea on exertion is a common complaint in patients with obesity, particularly in females, exercise prescriptions should be tailored with the goal of minimizing unpleasant respiratory sensations.

High-intensity interval exercise attenuates but does not eliminate endothelial dysfunction after a fast food meal.

We investigated whether two different bouts of high-intensity interval exercise (HIIE) could attenuate postprandial endothelial dysfunction. Thirteen young (27 ± 1 yr), nonexercise-trained men underwent three randomized conditions: 1) four 4-min intervals at 85-95% of maximum heart rate separated by 3 min of active recovery (HIIE 4 × 4), 2) 16 1-min intervals at 85-95% of maximum heart rate separated by 1 min of active recovery (HIIE 16 × 1), and 3) sedentary control. HIIE was performed in the afternoon, ~18 h before the morning fast food meal (1,250 kcal, 63g of fat). Brachial artery flow-mediated dilation (FMD) was performed before HIIE ( baseline 1), during fasting before meal ingestion ( baseline 2), and 30 min, 2 h, and 4 h postprandial. Capillary glucose and triglycerides were assessed at fasting, 30 min, 1 h, 2 h, and 4 h (triglycerides only). Both HIIE protocols increased fasting FMD compared with control (HIIE 4 × 4: 6.1 ± 0.4%, HIIE 16 × 1: 6.3 ± 0.5%, and control: 5.1 ± 0.4%, P < 0.001). For both HIIE protocols, FMD was reduced only at 30 min postprandial but never fell below baseline 1 or FMD during control at any time point. In contrast, control FMD decreased at 2 h (3.8 ± 0.4%, P < 0.001) and remained significantly lower than HIIE 4 × 4 and 16 × 1 at 2 and 4 h. Postprandial glucose and triglycerides were unaffected by HIIE. In conclusion, HIIE performed ~18 h before a high-energy fast food meal can attenuate but not entirely eliminate postprandial decreases in FMD. This effect is not dependent on reductions in postprandial lipemia or glycemia. NEW & NOTEWORTHY Two similar high-intensity interval exercise (HIIE) protocols performed ∼18 h before ingestion of a high-energy fast food meal attenuated but did not entirely eliminate postprandial endothelial dysfunction in young men largely by improving fasting endothelial function. Both HIIE protocols produced essentially identical results, suggesting high reproducibility of HIIE effects.

Validity of SenseWear® Armband v5.2 and v2.2 for estimating energy expenditure.

We compared SenseWear Armband versions (v) 2.2 and 5.2 for estimating energy expenditure in healthy adults. Thirty-four adults (26 women), 30.1 ± 8.7 years old, performed two trials that included light-, moderate- and vigorous-intensity activities: (1) structured routine: seven activities performed for 8-min each, with 4-min of rest between activities; (2) semi-structured routine: 12 activities performed for 5-min each, with no rest between activities. Energy expenditure was measured by indirect calorimetry and predicted using SenseWear v2.2 and v5.2. Compared to indirect calorimetry (297.8 ± 54.2 kcal), the total energy expenditure was overestimated (P < 0.05) by both SenseWear v2.2 (355.6 ± 64.3 kcal) and v5.2 (342.6 ± 63.8 kcal) during the structured routine. During the semi-structured routine, the total energy expenditure for SenseWear v5.2 (275.2 ± 63.0 kcal) was not different than indirect calorimetry (262.8 ± 52.9 kcal), and both were lower (P < 0.05) than v2.2 (312.2 ± 74.5 kcal). The average mean absolute per cent error was lower for the SenseWear v5.2 than for v2.2 (P < 0.001). SenseWear v5.2 improved energy expenditure estimation for some activities (sweeping, loading/unloading boxes, walking), but produced larger errors for others (cycling, rowing). Although both algorithms overestimated energy expenditure as well as time spent in moderate-intensity physical activity (P < 0.05), v5.2 offered better estimates than v2.2.

Postexercise Hypotension After Continuous, Aerobic Interval, and Sprint Interval Exercise.

We examined the effects of 3 exercise bouts, differing markedly in intensity, on postexercise hypotension (PEH). Eleven young adults (age: 24.6 ± 3.7 years) completed 4 randomly assigned experimental conditions: (a) control, (b) 30-minute steady-state exercise (SSE) at 75-80% maximum heart rate (HRmax), (4) aerobic interval exercise (AIE): four 4-minute bouts at 90-95% HRmax, separated by 3 minutes of active recovery, and (d) sprint interval exercise (SIE): six 30-second Wingate sprints, separated by 4 minutes of active recovery. Exercise was performed on a cycle ergometer. Blood pressure (BP) was measured before exercise and every 15-minute postexercise for 3 hours. Linear mixed models were used to compare BP between trials. During the 3-hour postexercise, systolic BP (SBP) was lower (p < 0.001) after AIE (118 ± 10 mm Hg), SSE (121 ± 10 mm Hg), and SIE (121 ± 11 mm Hg) compared with control (124 ± 8 mm Hg). Diastolic BP (DBP) was also lower (p < 0.001) after AIE (66 ± 7 mm Hg), SSE (69 ± 6 mm Hg), and SIE (68 ± 8 mm Hg) compared with control (71 ± 7 mm Hg). Only AIE resulted in sustained (>2 hours) PEH, with SBP (120 ± 9 mm Hg) and DBP (68 ± 7 mm Hg) during the third-hour postexercise being lower (p ≤ 0.05) than control (124 ± 8 and 70 ± 7 mm Hg). Although all exercise bouts produced similar reductions in BP at 1-hour postexercise, the duration of PEH was greatest after AIE.

Using a Verification Test for Determination of V[Combining Dot Above]O2max in Sedentary Adults With Obesity.

A constant-load exercise bout to exhaustion after a graded exercise test to verify maximal oxygen uptake (V[Combining Dot Above]O2max) during cycle ergometry has not been evaluated in sedentary adults with obesity. Nineteen sedentary men (n = 10) and women (n = 9) with obesity (age = 35.8 ± 8.6 years; body mass index [BMI] = 35.9 ± 5.1 kg·m; body fat percentage = 44.9 ± 7.2) performed a ramp-style maximal exercise test (ramp), followed by 5-10 minutes of active recovery, and then performed a constant-load exercise bout to exhaustion (verification test) on a cycle ergometer for determination of V[Combining Dot Above]O2max and maximal heart rate (HRmax). V[Combining Dot Above]O2max did not differ between tests (ramp: 2.29 ± 0.71 L·min, verification: 2.34 ± 0.67 L·min; p = 0.38). Maximal heart rate was higher on the verification test (177 ± 13 b·min vs. 174 ± 16 b·min; p = 0.03). Thirteen subjects achieved a V[Combining Dot Above]O2max during the verification test that was ≥2% (range: 2.0-21.0%; 0.04-0.47 L·min) higher than during the ramp test, and 8 subjects achieved a HRmax during the verification test that was 4-14 b·min higher than during the ramp test. Duration of verification or ramp tests did not affect V[Combining Dot Above]O2max results, but the difference in HRmax between the tests was inversely correlated with ramp test duration (r = -0.57, p = 0.01). For both V[Combining Dot Above]O2max and HRmax, differences between ramp and verification tests were not correlated with BMI or body fat percentage. A verification test may be useful for identifying the highest V[Combining Dot Above]O2max and HRmax during cycle ergometry in sedentary adults with obesity.

Physiological Responses to High-Intensity Interval Exercise Differing in Interval Duration.

We determined the oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), and blood lactate responses to 2 high-intensity interval exercise protocols differing in interval length. On separate days, 14 recreationally active males performed a 4 × 4 (four 4-minute intervals at 90-95% HRpeak, separated by 3-minute recovery at 50 W) and 16 × 1 (sixteen 1-minute intervals at 90-95% HRpeak, separated by 1-minute recovery at 50 W) protocol on a cycle ergometer. The 4 × 4 elicited a higher mean V[Combining Dot Above]O2 (2.44 ± 0.4 vs. 2.36 ± 0.4 L·min) and "peak" V[Combining Dot Above]O2 (90-99% vs. 76-85% V[Combining Dot Above]O2peak) and HR (95-98% HRpeak vs. 81-95% HRpeak) during the high-intensity intervals. Average power maintained was higher for the 16 × 1 (241 ± 45 vs. 204 ± 37 W), and recovery interval V[Combining Dot Above]O2 and HR were higher during the 16 × 1. No differences were observed for blood lactate concentrations at the midpoint (12.1 ± 2.2 vs. 10.8 ± 3.1 mmol·L) and end (10.6 ± 1.5 vs. 10.6 ± 2.4 mmol·L) of the protocols or ratings of perceived exertion (7.0 ± 1.6 vs. 7.0 ± 1.4) and Physical Activity Enjoyment Scale scores (91 ± 15 vs. 93 ± 12). Despite a 4-fold difference in interval duration that produced greater between-interval transitions in V[Combining Dot Above]O2 and HR and slightly higher mean V[Combining Dot Above]O2 during the 4 × 4, mean HR during each protocol was the same, and both protocols were rated similarly for perceived exertion and enjoyment. The major difference was that power output had to be reduced during the 4 × 4 protocol to maintain the desired HR.

Predictors of fat mass changes in response to aerobic exercise training in women.

Aerobic exercise training in women typically results in minimal fat loss, with considerable individual variability. We hypothesized that women with higher baseline body fat would lose more body fat in response to exercise training and that early fat loss would predict final fat loss. Eighty-one sedentary premenopausal women (age: 30.7 ± 7.8 years; height: 164.5 ± 7.4 cm; weight: 68.2 ± 16.4 kg; fat percent: 38.1 ± 8.8) underwent dual-energy x-ray absorptiometry before and after 12 weeks of supervised treadmill walking 3 days per week for 30 minutes at 70% of (Equation is included in full-text article.). Overall, women did not lose body weight or fat mass. However, considerable individual variability was observed for changes in body weight (-11.7 to +4.8 kg) and fat mass (-11.8 to +3.7 kg). Fifty-five women were classified as compensators and, as a group, gained fat mass (25.6 ± 11.1 kg to 26.1 ± 11.3 kg; p < 0.001). The strongest correlates of change in body fat at 12 weeks were change in body weight (r = 0.52) and fat mass (r = 0.48) at 4 weeks. Stepwise regression analysis that included change in body weight and body fat at 4 weeks and submaximal exercise energy expenditure yielded a prediction model that explained 37% of the variance in fat mass change (R = 0.37, p < 0.001). Change in body weight and fat mass at 4 weeks were moderate predictors of fat loss and may potentially be useful for identification of individuals who achieve less than expected weight loss or experience unintended fat gain in response to exercise training.

Potential Therapeutic Role of Respiratory Muscle Training in Dyspnea Management of Cancer Survivors: A Narrative Review.

Dyspnea is a disabling symptom presented in approximately half of all cancer survivors. From a clinical perspective, despite the availability of pharmacotherapies, evidence-based effective treatments are limited for relieving dyspnea in cancer survivors. Preliminary evidence supports the potential of respiratory muscle training to reduce dyspnea in cancer survivors, although large randomized controlled studies are warranted. The aims of this article were to review the relevant scientific literature on the potential therapeutic role of respiratory muscle training in dyspnea management of cancer survivor, and to identify possible mechanisms, strengths and limitations of the evidence as well as important gaps for future research directions.

The Effect of Body Armor on Pulmonary Function Using Plethysmography.

Military tactical athletes face the unique task of performing physically demanding occupational duties, often while wearing body armor. Forced vital capacity and forced expiratory volume measured using spirometry have been shown to decrease, while wearing plate-carrier style body armor, little is known about the comprehensive effects of wearing body armor on pulmonary function, including lung capacities. Further, the effects of loaded body armor vs. unloaded on pulmonary function are also unknown. Therefore, this study examined how loaded and unloaded body armor affects pulmonary function. Twelve college-aged males performed spirometry and plethysmography under three conditions (basic athletic attire [CNTL], unloaded plate carrier [UNL], and loaded plate carrier [LOAD]). Compared to CNTL, LOAD and UNL conditions significantly reduced functional residual capacity by 14% and 17%, respectively. Compared with CNTL, LOAD condition also showed a small but statistically significant lowered forced vital capacity (P = .02, d = 0.3), a 6% lower total lung capacity (P < .01, d = 0.5), and lowered maximal voluntary ventilation (P = .04, d = 0.4). A loaded plate-carrier style body armor exerts a restrictive effect on total lung capacity, and both loaded and unloaded body armor affects functional residual capacity, which could impact breathing mechanics during exercise. Resulting endurance performance decreases may need to be factored based on the style and loading of body armor, especially for longer-duration operations.

Acute Effects of Albuterol on Ventilatory Capacity in Children with Asthma.

BACKGROUND: Children with asthma may have a reduced ventilatory capacity, which could lead to symptoms and early termination of a cardiopulmonary exercise test (CPET). The purpose of this study was to examine the effects of short-acting beta agonist (albuterol) administration on estimated ventilatory capacity in children with asthma. METHODS: Fifteen children (eleven boys, 10.6 ± 0.9 years) completed spirometry at baseline, after 180 µg of albuterol, and after the CPET in this cross-sectional study. Ventilatory capacity was calculated from forced vital capacity (FVC) and isovolume forced expiratory time from 25 to 75% of FVC (isoFET25-75) as follows: FVC/2 × [60/(2 × isoFET25-75)]. Differences in outcome variables between baseline, after albuterol administration, and after the CPET were detected with repeated measures mixed models with Bonferroni post hoc corrections. RESULTS: Estimated ventilatory capacity was higher after albuterol (68.7 ± 21.2 L/min) and after the CPET (75.8 ± 25.6 L/min) when compared with baseline (60.9 ± 22.0 L/min; P = 0.003). Because forced vital capacity did not change, the increased ventilatory capacity was primarily due to a decrease in isoFET25-75 (i.e., an increase in mid-flows or isoFEF25-75). CONCLUSION: Albuterol administration could be considered prior to CPET for children with asthma with relatively well-preserved FEV1 values to increase ventilatory capacity pre-exercise and potentially avoid symptom-limited early termination of testing.

A Randomized Trial of Inspiratory Training in Children and Adolescents With Obesity.

Introduction: Children with obesity suffer excess dyspnea that contributes to sedentariness. Developing innovative strategies to increase exercise tolerance and participation in children with obesity is a high priority. Because inspiratory training (IT) has reduced dyspnea, we sought to assess IT in children with obesity. Methods: We conducted a 6-week randomized IT trial involving 8- to 17-year-olds with obesity. Participants were randomized 1:1 to either high [75% of maximal inspiratory pressure (MIP)] or low resistance control (15% of MIP) three times weekly. Assessments included adherence, patient satisfaction, and changes in inspiratory strength and endurance, dyspnea scores and total activity level. Results: Among 27 randomized, 24 (89%) completed the intervention. Total session adherence was 72% which did not differ between treatment groups. IT was safe, and more than 90% felt IT benefitted breathing and general health. IT led to a mean improvement (95% CI) in inspiratory strength measured by MIP of 10.0 cm H2O (-3.5, 23.6; paired t-test, p = 0.139) and inspiratory endurance of 8.9 (1.0, 16.8; paired t-test, p = 0.028); however, there was no significant difference between high- and low-treatment groups. IT led to significant reductions in dyspnea with daily activity (p < 0.001) and in prospectively reported dyspnea during exercise (p = 0.024). Among the high- versus low-treatment group, we noted a trend for reduced dyspnea with daily activity (p = 0.071) and increased daily steps (865 vs. -51, p = 0.079). Discussion: IT is safe and feasible for children with obesity and holds promise for reducing dyspnea and improving healthy activity in children with obesity. Breathe-Fit trial NCT05412134.

Treadmill walking economy is not affected by body fat and body mass index in adults.

To determine whether body fat and body mass index (BMI) affect the energy cost of walking (Cw; J/kg/m), ventilation, and gas exchange data from 205 adults (115 females; percent body fat range = 3.0%-52.8%; BMI range = 17.5-43.2 kg/m2) were obtained at rest and during treadmill walking at 1.34 m/s to calculate gross and net Cw. Linear regression was used to assess relationships between body composition indices, Cw, and standing metabolic rate (SMR). Unpaired t-tests were used to assess differences between sex, and one-way ANOVA was used to assess differences by BMI categories: normal weight, <25.0 kg/m2; overweight, 25.0-29.9 km/m2; and obese, ≥30 kg/m2. Net Cw was not related to body fat percent, fat mass, or BMI (all R2 ≤ 0.011). Furthermore, mean net Cw was similar by sex (male: 2.19 ± 0.30 J/kg/m; female: 2.24 ± 0.37 J/kg/m, p = 0.35) and across BMI categories (normal weight: 2.23 ± 0.36 J/kg/m; overweight: 2.18 ± 0.33 J/kg/m; obese: 2.26 ± 0.31, p = 0.54). Gross Cw and SMR were inversely associated with percent body fat, fat mass, and BMI (all R2 between 0.033 and 0.270; all p ≤ 0.008). In conclusion, Net Cw is not influenced by body fat percentage, total body fat, and BMI and does not differ by sex.

Effects of Obesity and Sex on Ventilatory Constraints during a Cardiopulmonary Exercise Test in Children.

PURPOSE: Ventilatory constraints are common during exercise in children, but the effects of obesity and sex are unclear. The purpose of this study was to investigate the effects of obesity and sex on ventilatory constraints (i.e., expiratory flow limitation (EFL) and dynamic hyperinflation) during a maximal exercise test in children. METHODS: Thirty-four 8-12-year-old children without obesity (18 females) and 54 with obesity (23 females) completed pulmonary function testing and maximal cardiopulmonary exercise tests. EFL was calculated as the overlap between tidal flow-volume loops during exercise and maximal expiratory flow-volume loops. Dynamic hyperinflation was calculated as the change in inspiratory capacity from rest to exercise. RESULTS: Maximal minute ventilation was not different between children with and without obesity. Average end-inspiratory lung volumes (EILV) and end-expiratory lung volumes (EELV) were significantly lower during exercise in children with obesity (EILV: 68.8 ± 0.7%TLC; EELV: 41.2 ± 0.5%TLC) compared with children without obesity (EILV: 73.7 ± 0.8%TLC; EELV: 44.8 ± 0.6%TLC; P < 0.001). Throughout exercise, children with obesity experienced more EFL and dynamic hyperinflation compared with those without obesity (P < 0.001). Also, males experienced more EFL and dynamic hyperinflation throughout exercise compared with females (P < 0.001). At maximal exercise, the prevalence of EFL was similar in males with and without obesity, however the prevalence of EFL in females was significantly different with 57% of females with obesity experiencing EFL compared with 17% of females without obesity (P < 0.05). At maximal exercise, 44% of children with obesity experienced dynamic hyperinflation compared with 12% of children without obesity (P = 0.002). CONCLUSIONS: Obesity in children increases the risk of developing mechanical ventilatory constraints such as dynamic hyperinflation and EFL. Sex differences were apparent with males experiencing more ventilatory constraints compared with females.

Body composition in early pubescent children with obesity: effects following 1 year of nonintervention.

Little is known about whether body composition changes differently between children with and without obesity following 1 year of nonintervention. Therefore, we investigated body composition in early pubescent children (8-12 yr) with and without obesity before and after a period of 1 year of nonintervention. Early pubescent children (8-12 yr; Tanner stage ≤ 3) with (body mass index, BMI ≥ 95th percentile) and without obesity (15th < BMI < 85th percentile) were recruited. At baseline, 88 children (n = 25 without obesity) completed dual-energy X-ray absorptiometry imaging (DXA) for body composition measurements [%body fat, fat mass, fat-free mass (FFM)]. One year later, 47 participants (n = 15 without obesity) returned for repeat testing. The children without obesity were older (11.0 ± 1.0 vs. 10.0 ± 1.2 yr; means ± SD) (P = 0.013). There was no group difference in height, and both groups increased in height similarly after 1 year (147.7 ± 8.9 to 154.5 ± 9.2 cm without vs. 145.6 ± 5.8 to 152.5 ± 5.9 cm with obesity) (P < 0.001). Weight was greater (P < 0.001) in children with obesity at baseline as was the increase in weight after 1 yr (9.25 vs. 5.82 kg) (interaction, P = 0.005). Fat mass increased by 4.4 kg in children with obesity and by 1.1 kg in children without obesity (interaction, P < 0.001). However, there was no difference in fat-free mass between those with and without obesity at baseline (29.9 ± 5.9 vs. 31.6 ± 4.8 kg) (P = 0.206) with both groups increasing similarly over 1 year (gain of 4.87 vs. 4.85 kg with and without obesity, respectively). Without intervention, the increase in fat mass is four times greater in children with obesity after 1 year as compared with children without obesity.NEW & NOTEWORTHY Little is known about changes in body composition in children with and without obesity following 1 year of nonintervention. We report that without intervention, fat mass gain is significantly greater in children with obesity after 1 year compared with those without obesity. Body mass index (BMI) and %body fat measurements after 1 year yielded no significant increase suggesting that BMI and %fat alone are not suitable measures for tracking changes in adiposity among children.

Static respiratory mechanics are unaltered in males and females with obesity.

We tested the hypothesis that independent of the obesity-related shift in lung volume subdivisions, obesity would not reduce the interrelationships of expiratory flow, lung volume, and static lung elastic recoil pressure in males and females. Simultaneous measurements of expiratory flow, volume, and transpulmonary pressure were continuously recorded while flow-volume loops of varying expiratory efforts were performed in a pressure-corrected, volume-displacement body plethysmograph in males and females with obesity. Static compliance curves were collected using the occlusion technique. Flow-volume, static pressure-volume, and static pressure-flow relationships were examined. Isovolume pressure-flow curves were constructed for the determination of the critical pressure for maximal flow. Data were compared with that collected in lean males and females. Individuals with obesity displayed a notable decrease in functional residual capacity. The interrelationships of flow, lung volume, static elastic recoil pressure, and the minimum pressure required for maximal expiratory flow in males and females with obesity were not different from that in lean males and females (all P > 0.05). Obesity does not alter the interrelationships of flow-volume-pressure of the lung in adult males and females (all P > 0.05). We further explored potential sex differences in static mechanics independent of obesity and observed that females have lower maximal expiratory flow due to a combination of smaller lungs and greater upstream flow resistance compared with males (all P ≤ 0.05).NEW & NOTEWORTHY The potential influence of obesity on the interrelationships between maximal expiratory flow, lung volume, and static lung elastic recoil pressure is unclear. These data show that the presence of obesity does not alter the relationship of flow and pressure across the mid-expiratory range in males and females. In addition, independent of obesity, females have smaller lungs and greater upstream flow resistance, which contributes to reduced maximal flow, when compared with males.

Inspiratory Muscle Rehabilitation Training in Pediatrics: What Is the Evidence?

Pulmonary rehabilitation is typically used for reducing respiratory symptoms and improving fitness and quality of life for patients with chronic lung disease. However, it is rarely prescribed and may be underused in pediatric conditions. Pulmonary rehabilitation can include inspiratory muscle training that improves the strength and endurance of the respiratory muscles. The purpose of this narrative review is to summarize the current literature related to inspiratory muscle rehabilitation training (IMRT) in healthy and diseased pediatric populations. This review highlights the different methods of IMRT and their effects on respiratory musculature in children. Available literature demonstrates that IMRT can improve respiratory muscle strength and endurance, perceived dyspnea and exertion, maximum voluntary ventilation, and exercise performance in the pediatric population. These mechanistic changes help explain improvements in symptomology and clinical outcomes with IMRT and highlight our evolving understanding of the role of IMRT in pediatric patients. There remains considerable heterogeneity in the literature related to the type of training utilized, training protocols, duration of the training, use of control versus placebo, and reported outcome measures. There is a need to test and refine different IMRT protocols, conduct larger randomized controlled trials, and include patient-centered clinical outcomes to help improve the evidence base and support the use of IMRT in patient care.

Repeatability of dyspnea measurements during exercise in women with obesity.

While the 0-10 Borg scale to rate perceived breathlessness (RPB) is widely used to assess dyspnea on exertion, the repeatability of RPB in women with obesity is unknown. We examined the repeatability of RPB in women with obesity during submaximal constant-load cycling following at least 10 weeks of normal daily life. Seventeen women (37 ± 7 yr; 34.6 ± 4.5 kg/m2) who rated their breathlessness as 3 on the Borg scale (i.e., "moderate") during 60 W submaximal cycling repeated the same test following 19 ± 9 weeks of normal living. Mean body weight (93.8 ± 16.1 vs. 93.6 ± 116.8 kg, p = 0.94) and RPB (3.0 ± 0.0 vs. 3.1 ± 1.4, p = 0.80) did not differ between pre- and post-normal living periods. We demonstrate that subjective ratings of breathlessness are repeatable for the majority of subjects and can be used to accurately assess DOE during submaximal constant-load cycling in women with obesity.

Mechanical effects of obesity on central and peripheral airway resistance in nonasthmatic early pubescent children.

BACKGROUND: In children, obesity typically reduces functional residual capacity (FRC), which reduces airway caliber and increases airway resistance. Whether these obesity-related changes in respiratory function can alter bronchodilator responsiveness is unknown. OBJECTIVE: To investigate bronchodilator responsiveness in nonasthmatic children with and without obesity. METHODS: Seventy nonasthmatic children, 8-12 years old, without (n = 19) and with (n = 51) obesity, completed spirometry, impulse oscillometry, and airway resistance measurements through plethysmography pre/post 360 µg of inhaled albuterol. FRC was assessed pre albuterol. A two-way analysis of variance determined the effects of obesity (group) and inhaled albuterol (pre-post) on outcome measures. RESULTS: FRC (%total lung capacity) was 16% lower in children with obesity compared with those without obesity. There was no significant group by pre-post albuterol interaction on any outcome variables. Albuterol inhalation reduced total, central and peripheral airway resistance and increased airway reactance (i.e., less negative) to a similar degree in children with and without obesity. In children with obesity, airway resistance was increased whether measured by impulse oscillometry or plethysmography. However, once airway resistance was adjusted for lung volumes (i.e., specific airway resistance or sRaw ), there were no differences between children with and without obesity. In addition, significant but moderate associations were detected between chest mass and FRC (r = -0.566; p < 0.001), FRC and total airway resistance (i.e., Raw ; r = -0.445; p < 0.001). CONCLUSIONS: In nonasthmatic early pubescent children, obesity increases total, central, and peripheral respiratory system resistance. However, the added respiratory system resistance and low lung volume breathing with obesity are not sufficient to reduce bronchodilator responsiveness.

Quantification and Verification of Cardiorespiratory Fitness in Adults with Prehypertension.

BACKGROUND: Low cardiorespiratory fitness is associated with increased risk of hypertension and atherosclerosis in adults with prehypertension. The purpose of this study was to quantify cardiorespiratory fitness and to examine the utility of supramaximal constant-load verification testing for validating maximal oxygen uptake (VO2max) attainment in adults with prehypertension. METHODS: Eleven adults (four women) with prehypertension (22.5 ± 2.9 y; body mass index (BMI): 24.6 ± 3.2 kg·m2) underwent an incremental exercise test followed 15 min later by a verification test at 105% of maximal work rate on a cycle ergometer. RESULTS: There was no statistical difference in VO2 between the incremental (2.23 ± 0.54 L·min-1) and verification tests (2.28 ± 0.54 L·min-1; p = 0.180). Only three out of eleven participants had a higher VO2 during the verification when compared with the incremental test. If the verification test had not been conducted, one participant would have been incorrectly classified as having low cardiorespiratory fitness based on incremental test results alone. CONCLUSIONS: Verification testing validates the attainment of VO2max and can potentially reduce the over-diagnosis of functional impairment (i.e., deconditioning) in adults with prehypertension.