Maximal Minute Ventilation Research Articles

Effects of different exercise regimens on prognosis of patients with chronic obstructive pulmonary disease: a systematic reviews and meta-analysis

Introduction Skeletal muscle dysfunction is a significant factor contributing to exercise limitation in patients with chronic obstructive pulmonary disease (COPD). Although exercise training is often recommended to enhance patient outcomes, there continues to be ongoing debate regarding its exact effects. Objective The aim of this study is to evaluate the effectiveness of endurance exercise, strength training and combined exercise on cardiorespiratory fitness (including maximal oxygen uptake, maximal minute ventilation, and the 6-minute walk test), strength of lower limbs (measured by leg press), and quality of life (using the COPD Assessment Test) in patients with COPD. By conducting a systematic review and meta-analysis of randomized controlled trials (RCTs), our objective is to provide tailored training methods and intensity recommendations for patients with COPD in order to improve their quality of life. Methods The meta-analysis included 10 randomized controlled trials (RCTs) of exercise rehabilitation programs involving 180 patients with COPD that were retrieved from electronic databases (PubMed, Cochrane Library, and Embase). Two reviewers independently assessed the topical relevance, trial quality, and extracted data for the meta-analysis. Results Meta-analysis showed that primary outcomes representing exercise endurance were elevated under different exercise interventions compared to pre-test, such as maximal oxygen uptake (VO2max (ml/kg/min)) [SMD = 0.40, 95% CI (0.15, 0.64)] and the 6-min walk test (6MWT) [MD = 33.90, 95% CI (25.25, 42.55)], and primary outcomes representing strength also increased, such as leg press (1RM) [MD = 24.59, 95% CI (16.08, 33.11)], while secondary outcomes such as assessments of life such as the COPD Assessment Test (CAT) recovered [MD = 2.51, 95% CI (2.01, 3.00)], with all differences being statistically significant (p < 0.05). However, Maximum minute ventilation (VEmax (L)) [MD = 0.91, 95%CI (3.61, 5.43)] was not statistically significant (p > 0.05) when compared with the post-test data. The sensitivity test data were stable, and the results were reliable. We subgrouped the data from different types of exercise interventions and found that different types of exercise affected the experimental results. Conclusion Exercise interventions have a positive effect on the treatment of patients with COPD, significantly improving functional capacity, aerobic capacity, and exercise tolerance, but they should be individualized and developed according to the patient’s condition to achieve the best therapeutic effect.

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

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. Thirty-four 8- to 12-yr-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. 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). 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.

High-intensity interval training improves respiratory and cardiovascular adjustments before and after initiation of exercise.

Purpose: High-intensity interval training (HIIT) may induce training-specific physiological adaptations such as improved respiratory and cardiovascular adjustments before and after the onset of high-intensity exercise, leading to improved exercise performance during high-intensity exercise. The present study investigated the effects of HIIT on time-dependent cardiorespiratory adjustment during maximal exercise and before and after initiation of high-intensity exercise, as well as on maximal exercise performance. Methods: 21 healthy male college students were randomly assigned to HIIT group (n = 11) or control group (n = 10). HIIT group performed training on a cycle ergometer once a week for 8 weeks. The training consisted of three bouts of exercise at 95% maximal work rate (WRmax) until exhaustion. Before and after the HIIT program, dynamic cardiorespiratory function was investigated by ramp and step exercise tests, and HIIT-induced cardiac morphological changes were assessed using echocardiography. Results: HIIT significantly improved not only maximal oxygen uptake and minute ventilation, but also maximal heart rate (HR), systolic blood pressure (SBP), and time to exhaustion in both exercise tests (p < 0.05). Time-dependent increases in minute ventilation (VE) and HR before and at the start of exercise were significantly enhanced after HIIT. During high-intensity exercise, there was a strong correlation between percent change (from before to after HIIT program) in time to exhaustion and percent change in HRmax (r = 0.932, p < 0.001). Furthermore, HIIT-induced cardiac morphological changes such as ventricular wall hypertrophy was observed (p < 0.001). Conclusion: We have demonstrated that HIIT at 95% WRmax induces training-specific adaptations such as improved cardiorespiratory adjustments, not only during maximal exercise but also before and after the onset of high-intensity exercise, improvement of exercise performance mainly associated with circulatory systems.

Persistence of expiratory flow limitations between normoxia and hypoxia

Introduction&#x0D; Expiratory flow limitation (EFL) refers to the inability to generate higher airflow despite greater respiratory effort and is common in both men and women. In normoxic condition, EFL is contingent upon an imbalance between ventilatory demands and capacity. Since hypoxia is known to alter ventilatory drive and pattern, it may influence the development of EFL. Therefore, the aim of this study was to investigate the origin of EFL in hypoxia and its repeatability and persistence during exercise in hypoxia.&#x0D; Method&#x0D; Fifty-one healthy active individuals (27 men and 24 women) performed a lung function test and a maximal incremental exercise test on a cycle-ergometer in normoxia and hypoxia (inspired oxygen fraction = 0.14) on two separate visits. Ventilatory capacity, assessed using the slope ratio (SR), were evaluated from maximal flow volume curve analyses.&#x0D; Results&#x0D; During exercise in normoxia, 28 participants exhibited EFL (55%). Another set of 28 participants exhibited EFL in hypoxia but they were not all the same individuals as those in normoxia. In normoxia, both SR and maximum minute ventilation (V̇E) were higher in the EFL group than the non-EFL group (p = 0.029 and p &lt;0.001; respectively). However, in hypoxia, only maximum V̇E was higher in the EFL group compared to non-EFL group (p = 0.006).&#x0D; Participants were then classified into 4 groups according to the occurrence of EFL in both normoxia and hypoxia: non-EFL in both conditions (non-EFLN/H, n = 18), EFL in both conditions (EFLN/H, n = 23), EFL developed only in normoxia (EFLN+/H-, n = 5), EFL developed only in hypoxia (EFLN-/H+, n = 5).&#x0D; The EFLN+/H- group showed different V̇E changes between normoxia and hypoxia (-13.5 ± 7.8%) compared to the EFLN-/H+ (+6.7 ± 6.3%) and the non-EFLN/H groups (+5.1 ± 10.3%; p = 0.004 and p &lt; 0.001, respectively). The difference with the EFLN/H (-1.7 ± 8.0%) did not reach significance (p = 0.057). Breathing frequency changes between normoxia and hypoxia were different between the EFLN-/H+ group (+4.6 ± 12.9%) and the EFLN+/H- group (-11.7 ± 13.1%) (p = 0.039). Normoxia to hypoxia decrease in maximal oxygen uptake was not significantly larger in the EFL N+/H- group (-18.4 ± 3.4%) than in the EFL EFLN-/H+ group (-10.3 ± 5.4%; p = 0.087).&#x0D; Discussion/Conclusion&#x0D; Hypoxia altered EFL development since there was a shift in the individuals who exhibited flow limitation between normoxia and hypoxia. This can be attributed to the extent of ventilatory reserve utilization. Specifically, those who developed EFL exclusively in hypoxia exhibited a significant increase in V̇E whereas those with EFL only in normoxia experienced a significant decrease in V̇E. Notably in hypoxia, the ventilatory capacity did not differ between individuals with EFL and those without. This observation suggests that in hypoxia, the development of EFL relied more on ventilatory demands than on ventilatory capacity.

Effects of Different Warm-up Protocols on the Cardiopulmonary Responses to Exercise Testing in Youth

The aim of this study was to compare the warm-up effects of a treadmill walking warm-up (TW) with a dynamic warm-up (DW) on the responses to cardiopulmonary exercise testing (CPET) in youth. A sample of 16 active youth (age 13.6 ± 1.8 yr) were tested for peak oxygen uptake (VO2 peak) using the Fitkids treadmill test protocol on 2 nonconsecutive days following different 6-min warm-up procedures. The TW consisted of walking on a treadmill at 2.2 mph and 0% grade whereas the DW consisted of 12 bodyweight exercises with a 2 kg medicine ball. Maximal heart rate (HR) was significantly higher following DW vs TW (200.8 ± 6.16 vs. 197.9 ± 7.3 bpm, respectively; p &lt; 0.05), whereas no significant differences were found between DW and TW for VO2 peak (50.5 ± 9.9 vs 50.6 ± 11.1 ml/kg/min), maximal minute ventilation (VE; 93.0 ±21.4 vs. 92.7 ±21.2 L/min), maximal respiratory exchange ratio (1.19 ± 0.08 vs 1.22 ± 0.08), and total exercise test time (668.1 ± 103.5 vs 686.3 ± 97.0 s), respectively. During the Fitkids treadmill test protocol HR and VE were significantly higher following DW vs TW at stage 1, stage 2, stage 3 and stage 4, and oxygen uptake was significantly higher following DW vs TW during stage 1 (all p &lt; 0.05). Findings indicate a DW elicits a higher maximal HR and higher submaximal HR, VE, and oxygen uptake values than TW during CPET in youth, although no differences in VO2 peak were observed.

Ventilatory response to added dead space in infants exposed to second-hand smoke in pregnancy

Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. In utero nicotine exposure has been shown to blunt the infant ventilatory response to hypercapnia, which could increase the risk of sudden infant death syndrome. The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. The aim of this study was to assess ventilatory response to added dead-space (inducing hypercapnia) in infants with second-hand smoke exposure during pregnancy, in infants whose mothers smoked and in controls (non-smoke exposed). Infants breathed through a face mask and specialised “tube-breathing” circuit, incorporating a dead space of 4.4 ml/kg body weight. The maximum minute ventilation (MMV) during added dead space breathing was determined and the time taken to achieve 63% of the MMV calculated (the time constant (TC) of the response). Infants were studied on the postnatal ward prior to discharge home. Thirty infants (ten in each group) were studied with a median gestational age of 39 [range 37–41] weeks, birthweight of 3.1 [2.2–4.0] kg, and postnatal age of 33 (21–62) h. The infants whose mothers had second-hand smoke exposure (median TC 42 s, p = 0.001), and the infants of cigarette smoking mothers (median TC 37 s, p = 0.002) had longer time constants than the controls (median TC 29 s). There was no significant difference between the TC of the infants whose mothers had second-hand smoke exposure and those whose mothers smoked (p = 0.112). Conclusion: Second-hand smoke exposure during pregnancy was associated with a delayed newborn ventilatory response.What is Known:• Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control.• The potential impact of maternal second-hand smoke exposure, however, has not yet been determined.What is New:• We have assessed the ventilatory response to added dead-space (inducing hypercapnia) in newborns with second-hand smoke exposure during pregnancy, in infants whose mothers smoked, and in controls (non-smoke exposed).• Maternal second-hand smoke exposure, as well as maternal smoking, during pregnancy was associated with a delayed newborn ventilatory response.

The effects of cloth face masks on cardiorespiratory responses and VO2 during maximal incremental running protocol among apparently healthy men

We aimed to determine the effects of wearing a cloth face mask on cardiorespiratory response, peak oxygen uptake (Vo2), respiratory muscle effort, and exercise tolerance during incremental exercise. The study had a randomized crossover design: 11 apparently healthy young men performed the Bruce protocol treadmill test in two conditions, wearing a cloth face mask (CFM) and without CFM (CON), in random order. Minute ventilation and oxygen uptake were measured using a mass spectrometry metabolic analyzer; cardiac output (CO) was measured using an impedance CO monitor; and mouth pressure (Pm) was measured and calculated as an integral Pm to assess respiratory muscle effort. Maximal minute ventilation was 13.4 ± 10.7% lower in the CFM condition than in the CON condition (P < 0.001). The peak Vo2 (52.4 ± 5.6 and 55.0 ± 5.1 mL/kg/min in CFM and CON, respectively) and CO were not significantly different between the two conditions. However, the integral value of Pm was significantly higher (P = 0.02), and the running time to exhaustion was 2.6 ± 3.2% lower (P = 0.02) in the CFM condition than in the CON condition. Our results suggest that wearing a cloth face mask increased respiratory muscle effort and decreased ventilatory volume in healthy young men; however, Vo2 remained unchanged. Exercise tolerance also decreased slightly.

Abstract 13884: Cardiopulmonary Exercise Testing Delineates Underlying Mechanisms of “Good” and “Poor” Exercise Performance in Post-Fontan Patients

Background: Fontan patients have limited exercise capacity primarily due to an absence of subpulmonary ventricle by which ventricular filling is hindered in response to incremental exercise. Little is understood as to how to improve exercise performance in Fontan patients. Methods: Cardiopulmonary exercise testing (CPET) in Fontan patients were studied retrospectively. The patients were divided into “Good” and “Poor” performance by peak oxygen consumption (pVO2) at 35 and 30 ml/kg/min for males and females, respectively. Data are shown as mean ± standard deviation. Results: Table 1 presents demographic data and CPET results of males and females with “Good” and “Poor” exercise performance (total 36 patients). Ventilatory anaerobic threshold (VAT) and peak work rate (pWR) were significantly lower in male “Poor” group than in male “Good” group whereas no significant difference was noted in female groups other than pVO2. A specific trend of each group emerged when weight (kg)-pVO2 (L/min) and maximum minute ventilation (maxVE: L/min)-pVO2 (L/min) relationship were assessed, which indicated that “Good” Fontan had higher skeletal muscle mass effects in given weight and better ventilatory efficiency for oxygenation, respectively, than “Poor” group (Figure 1). Conclusions: Under the same single ventricle physiology which mitigates ventricular filling, some Fontan patients showed better exercise performance than others due to higher skeletal muscle mass effects and better ventilatory efficiency for oxygenation. A simple method of plotting of 2 CPET parameters may be useful in assessing improvement in exercise performance by muscle and breathing training in Fontan patients.

A Comparison of Warm-Up Effects on Maximal Aerobic Exercise Performance in Children.

The aim of this study was to compare the warm-up effects of treadmill walking (TW) with a dynamic (DY) bodyweight warm-up on maximal aerobic exercise performance in children. Sixteen children (10.9 ± 1.5 vrs) were tested for peak oxygen uptake (VO2 peak) on 2 nonconsecutive days following different 6 min warm-up protocols. TW consisted of walking on a motor-driven treadmill at 2.2 mph and 0% grade whereas the DY warm-up consisted of 9 body weight movements including dynamic stretches, lunges, and jumps. Maximal heart rate was significantly higher following DY than TW (193.9 ± 6.2 vs. 191.6 ± 6.1 bpm, respectively; p = 0.008). VO2 peak (54.8 ± 9.6 vs. 51.8 ± 8.7 mL/kg/min; p = 0.09), maximal minute ventilation (68.9 ± 14.8 vs. 64.9 ± 9.4 L/min; p = 0.27), maximal respiratory exchange ratio (1.12 ± 0.1 vs. 1.11 ± 0.1; p = 0.85) and total exercise time (614.0 ± 77.1 vs. 605 ± 95.0 s; p = 0.55) did not differ significantly between DY and TM warm-ups, respectively. These findings indicate that the design of the warm-up protocol can influence the heart rate response to maximal aerobic exercise and has a tendency to influence VO2 peak. A DY warm-up could be a viable alternative to a TW warm-up prior to maximal exercise testing in children.

The Evaluation of Functional Abilities Using the Modified Fullerton Functional Fitness Test Is a Valuable Accessory in Diagnosing Men with Heart Failure

The assessment of functional abilities reflects the ability to perform everyday life activities that require specific endurance and physical fitness. The Fullerton functional fitness test (FFFT) seems to be the most appropriate for assessing physical fitness in heart failure (HF) patients. The study group consisted of 30 consecutive patients hospitalized for the routine assessment of HF with a reduced ejection fraction (HFrEF). They formed the study group, and 24 healthy subjects formed the control group. Each patient underwent a cardiopulmonary exercise test (CPET), transthoracic echocardiography and FFFT modified by adding the measurement of the handgrip force of the dominant limb with the digital dynamometer. The HF patients had significantly lower peak oxygen uptake (peakVO2), maximal minute ventilation, and higher ventilatory equivalent (VE/VCO2). The concentrations of B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) were significantly higher in the study group. The results of all the FFFT items were significantly worse in the study group. FFFT parameters, together with the assessment of the strength of the handgrip, strongly correlated with the results of standard tests in HF. FFFT is an effective and safe tool for the functional evaluation of patients with HFrEF. Simple muscle strength measurement with a hand-held dynamometer can become a convenient and practical indicator of muscle strength in HF patients.

Effects of different exercise training programs on the functional performance in fibrosing interstitial lung diseases: A randomized trial.

We aimed to compare the effects of different aerobic exercise training (ET) programs on respiratory performance, exercise capacity, and quality of life in fibrosing interstitial lung diseases (f-ILD). A case-control study where 31 patients with f-ILD diagnosis based on chest high-resolution computed tomography were recruited from Main Alexandria University hospital-Egypt. Ten patients were randomly assigned for only lower limbs (LL) endurance training program, and 10 patients for upper limbs, lower limbs, and breathing exercises (ULB) program for consecutive 18 sessions (3 sessions/week for 6 consecutive weeks). Eleven patients who refused to participate in the ET program were considered as control. All patients were subjected for St George's respiratory questionnaire (SGRQ), 6-minute walk test (6-MWT), forced spirometry and cardiopulmonary exercise testing (CPET) before and after ET programs. Fibrosing non-specific interstitial pneumonia (NSIP) and collagenic associated-ILD were the commonest pathologies among the ET groups (30% each) with mean age of 44.4±12.25 and 41.90±7.58 years for LL and ULB groups respectively and moderate-to-severe lung restriction. 6-MWT and SGRQ significantly improved after both ET programs (p<0.001). Peak oxygen consumption (VO2) improved significantly after both LL training (median of 22 (interquartile range (IQR) = 17.0-24.0) vs. 17.5 (IQR = 13.0-23.0) ml/kg/min, p = 0.032) and ULB training (median of 13.5 (IQR = 11.0-21.0) vs. 10.5 (IQR = 5.0-16.0) ml/kg/min, p = 0.018). Further, maximal work load and minute ventilation (VE) significantly improved after both types of ET training (p<0.05); however, neither ventilation equivalent (VE/VCO2) nor FVC% improved after ET (p = 0.052 and 0.259 respectively). There were no statistically significant important differences between LL and ULB training programs regarding 6-MWT, SGRQ or CPET parameters (p>0.05). ET was associated with improvements in exercise capacity and quality of life in f-ILD patients irrespective of the type of ET program provided.

Exploring the Anthropometric, Cardiorespiratory, and Haematological Determinants of Marathon Performance

AimWe aimed to investigate the main anthropometric, cardiorespiratory and haematological factors that can determine marathon race performance in marathon runners.MethodsForty-five marathon runners (36 males, age: 42 ± 10 years) were examined during the training period for a marathon race. Assessment of training characteristics, anthropometric measurements, including height, body weight (n = 45) and body fat percentage (BF%) (n = 33), echocardiographic study (n = 45), cardiopulmonary exercise testing using treadmill ergometer (n = 33) and blood test (n = 24) were performed. We evaluated the relationships of these measurements with the personal best marathon race time (MRT) within a time frame of one year before or after the evaluation of each athlete.ResultsThe training age regarding long-distance running was 9 ± 7 years. Training volume was 70 (50–175) km/week. MRT was 4:02:53 ± 00:50:20 h. The MRT was positively associated with BF% (r = 0.587, p = 0.001). Among echocardiographic parameters, MRT correlated negatively with right ventricular end-diastolic area (RVEDA) (r = −0.716, p < 0.001). RVEDA was the only independent echocardiographic predictor of MRT. With regard to respiratory parameters, MRT correlated negatively with maximum minute ventilation indexed to body surface area (VEmax/BSA) (r = −0.509, p = 0.003). Among parameters of blood test, MRT correlated negatively with haemoglobin concentration (r = −0.471, p = 0.027) and estimated haemoglobin mass (Hbmass) (r = −0.680, p = 0.002). After performing multivariate linear regression analysis with MRT as dependent variable and BF% (standardised β = 0.501, p = 0.021), RVEDA (standardised β = −0.633, p = 0.003), VEmax/BSA (standardised β = 0.266, p = 0.303) and Hbmass (standardised β = −0.308, p = 0.066) as independent variables, only BF% and RVEDA were significant independent predictors of MRT (adjusted R2 = 0.796, p < 0.001 for the model).ConclusionsThe main physiological determinants of better marathon performance appear to be low BF% and RV enlargement. Upregulation of both maximum minute ventilation during exercise and haemoglobin mass may have a weaker effect to enhance marathon performance.Clinical Trial Registrationwww.ClinicalTrials.gov, identifier NCT04738877.

3-Week passive acclimation to extreme environmental heat (100± 3°C) in dry sauna increases physical and physiological performance among young semi-professional football players.

This manuscript aims to evaluate the influence of a novel passive heat acclimation program among human participants in the physical performance, as well as in several physiological parameters. 36 male football players were acclimated using a dry sauna bath to extreme hot (100±3°C), performing a total of nine sauna sessions with a weekly frequency of three sessions. The players were randomly into the sauna group (SG; n=18; age: 20.69±2.09 years) and the control group (CG; n=18; age: 20.23±1.98 years). All participants performed maximal effort test until exhaustion as well as hamstring flexibility test before and after the acclimation program. Anthropometric, respiratory, circulatory, hematological and physiological variables were evaluated at the beginning and at the end of the survey. Statistical analysis consisted of a Mann-Whitney U test to determine differences between groups at the beginning and at the end of the survey and a Wilcoxon test for paired samples to compare the differences for each group separately. Additionally, size effects of the pre-post acclimation changes were calculated. After the acclimation program SG participants experienced a diminution in body weight (p<0.01), body mass index (p<0.01), body fat (p<0.05) and fat percentage (p<0.05) decreased. Hamstring flexibility (p<0.05) and work capacity (p<0.05) increased. External basal temperature decreased (p<0.05) as well as post-exercise systolic and diastolic blood pressures (p<0.05). Finally, maximal oxygen uptake (ml Kg-1 min-1) (p<0.05), maximal minute ventilation (p<0.05) and maximal breath frequency (p<0.05) increased at the end of the intervention. There were no significant changes in the CG in any variable. Favorable adaptations have been observed in this survey, suggesting a beneficial effect of extreme heat acclimation on physical performance. Several of the observed responses seem interesting for sport performance and health promotion as well. However, this is a novel, extreme protocol which requires further research.

Exploring the physiological determinants of marathon performance

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ESPA 2014-2020 Background/Introduction: Long-time endurance exercise training leads to cardiovascular, respiratory, haematological and neuromuscular adaptations. The relative contribution of these adaptations to running performance in long-distance races remains to be elucidated in an integrative manner. Purpose The study of the relationship of marathon performance with anthropometric, cardiorespiratory and haematological adaptations. Methods Thirty-one marathon runners (26 males, age: 42 ± 9 years) were examined within 3 weeks before Athens marathon race (42.195 km). Assessment of training characteristics, anthropometric measurements, including height, body weight and body fat percentage, echocardiographic study, cardiopulmonary exercise testing using treadmill ergometer and blood test were performed. Results Training age was 11(1-39) years. Body fat percentage(BFP) was 17.3 ± 7.1% and body weight-indexed maximum oxygen uptake(VO2max) was 52.6 ± 8.9 mL/kg/min. Marathon race time(MRT) was 3:59:01(2:47:17-5:31:32). Among anthropometric measurements, MRT was positively associated with BFP(r= 0.561, p = 0.002) and body fat mass(r = 0.514, p = 0.005), even after adjustment for VO2max or oxygen uptake at first(VO2-VT1) or second(VO2-VT2) ventilatory threshold, implying an effect of BFP on running economy. Among echocardiographic parameters, MRT correlated negatively with right ventricular end-diastolic area(RVEDA) (r = -0.707, p &amp;lt; 0.001) and ratio of early to late diastolic transtricuspid flow velocity(TVE/A) (r= -0.430, p = 0.025). MRT correlated negatively with body weight-indexed VO2max (r= -0.692, p &amp;lt; 0.001), VO2-VT1 (r= -0.426, p = 0.019) and VO2-VT2 (r= -0.688, p &amp;lt; 0.001). MRT correlated negatively with maximum minute ventilation(VEmax) (r= -0.418, p = 0.022), VEmax indexed for body surface area(BSA) (r= -0.456, p= 0.011), maximum tidal volume(Vtmax) indexed for BSA(r= -0.436, p = 0.018) and oxygen uptake efficiency slope(OUES) (r= -0.529, p = 0.003). MRT was not associated with haemoglobin concentration. RVEDA correlated positively with maximum oxygen pulse (r = 0.653, p = 0.001), which is an estimate of stroke volume during exercise, and OUES(r = 0.534, p = 0.009). After performing multivariate linear regression analysis with MRT as dependent variable and BFP(standardized β=0.495, p = 0.001), RVEDA(standardized β= -0.550, p = 0.001) and Vtmax indexed for BSA(standardized β= -0.110, p = 0.418) as independent variables, only BFP and RVEDA were significant independent predictors of MRT(adjusted R2 = 0.667, p &amp;lt; 0.001 for the model). Conclusions The results of the present study demonstrated that the main cardiorespiratory adaptation that could predict a better marathon performance was right ventricular dilatation, through the increase in stroke volume during exercise, whereas upregulation of tidal volume during exercise was found to be a weaker predictor. The principal anthropometric determinant of marathon performance appears to be body fat percentage, via the influence on running economy. Abstract Figure 1

Effects of Weekly Interval Training at High Intensity interval training on Dynamic Cardiorespiratory Responses to Exercise

Purpose Previously we reported that high-intensity interval training (HIIT) at 80% maximal work-rate (WRmax), even when performed at a low frequency of once a week, markedly improves maximal cardiorespiratory function and maximal performance time (Med Sci Sports Exerc. 2015). However, it has not been determined whether more intense interval exercise training will have the similar effect on maximal oxygen uptake (VO2max) or alter the dynamics of the cardiorespiratory response during maximal exercise. The purpose of this study was to examine whether or not the same effect can be obtained, even with HIIT at 95%WRmax for 8 weeks which further increased exercise intensity than the previous study. Methods Seventeen healthy male college students were randomly assigned to one of the two following groups; high-intensity interval training group (HIT; n = 9) and control group (n = 8). HIT group performed the training on a cycle ergometer once a week for 8 weeks. The training was consisted of three bouts until volitional fatigue at 95%WRmax. Cardiorespiratory function during maximal ramp and step (high-intensity) exercise test was investigated before and after the intervention period. Results The training resulted in increased VO2max (+9%, p = 0.037), maximal heart rate (+4%, p = 0.023) and maximal minute ventilation (+19%, p = 0.007) during maximal ramp test, respectively. Significant changes in the dynamic response of heart rate and blood pressure at the onset of high-intensity exercise were observed after the training program compared with baseline, and improvement in exhaustion time was also observed (+ 93%, P < 0.001). In addition, increased left ventricular posterior wall thickness at rest was also observed after training (+12%, p = 0.004). Conclusion The present results indicate that more intense HIIT performed at a low frequency once a week not only increased maximal cardiorespiratory function and exercise performance, but also induced cardiovascular adaptation in the enhancement of heart rate and blood pressure response during step exercise, as well as induces cardiac morphological adaptations involving left ventricular hypertrophy, as we have already found in previous studies.

Elevated expression of miR-146 involved in regulating mice pulmonary dysfunction after exposure to PM2.5.

Exposure to atmospheric fine particulate matter has short-term and long-term adverse effects on pulmonary function, especially PM2.5; however, early lung function impairment is not easily detected in time. Notably, microRNAs (miRNAs) have been classified as novel biomarkers for diseases related to PM. Thus, the purpose of this study was to investigate whether miR-146 was related to the decline of lung function after exposure to air pollution. Thirty BALB/c mice were subjected to different concentrations of PM2.5 by noninvasive tracheal instillation for 56 days (two times one week), after which we detected the histopathological changes of mice lung, pulmonary functions, pro-inflammatory factors levels in bronchoalveolar lavage fluid (BALF) and lung tissue homogenate, and the relative expression of microRNA-146a and -146b. When BALB/c mice were exposed to 10 mg/kg PM2.5, severe changes such as widened alveolar interval and diffuse infiltration of macrophages with engulfed PM2.5 particles (dust cells) were found. Peak inspiratory flow (PIF) and peak expiratory flow (PEF) were decreased significantly. Expiratory resistance (Re) and inspiratory resistance (Ri) were increased significantly in the 5 mg/kg and 10 mg/kg PM2.5 groups, meanwhile lung resistance increased and MVV (maximum minute ventilation) decreased from the general tendency; however, pro-inflammatory factors interleukin-6 (IL-6), interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) were increased dramatically. MiR-146a and miR-146b were elevated remarkably in the PM2.5 groups compared to the NS group. We also found miR-146 had negative relationships with PIF and PEF, especially miR-146b. Thus, elevated miR-146a and miR-146b may have a relationship with pulmonary dysfunction after PM2.5 chronic exposure.

Ventilatory and chronotropic incompetence during incremental and constant load exercise in end-stage renal disease: a comparative physiology study.

Maximal O2 uptake is impaired in end-stage renal disease (ESRD), reducing quality of life and longevity. While determinants of maximal exercise intolerance are well defined, little is known of limitation during submaximal constant load exercise. By comparing individuals with ESRD and healthy controls, the aim of this exploratory study was to characterize mechanisms of exercise intolerance in participants with ESRD by assessing cardiopulmonary physiology at rest and during exercise. Resting spirometry and echocardiography were performed in 20 dialysis-dependent participants with ESRD (age: 59 ± 12 yr, 14 men and 6 women) and 20 healthy age- and sex-matched controls. Exercise tolerance was assessed with ventilatory gas exchange and central hemodynamics during a maximal cardiopulmonary exercise test and 30 min of submaximal constant load exercise. Left ventricular mass (292 ± 102 vs. 185 ± 83 g, P = 0.01) and filling pressure (E/e': 6.48 ± 3.57 vs. 12.09 ± 6.50 m/s, P = 0.02) were higher in participants with ESRD; forced vital capacity (3.44 ± 1 vs. 4.29 ± 0.95 L/min, P = 0.03) and peak O2 uptake (13.3 ± 2.7 vs. 24.6 ± 7.3 mL·kg-1·min-1, P < 0.001) were lower. During constant load exercise, the relative increase in the arterial-venous O2 difference (13 ± 18% vs. 74 ± 18%) and heart rate (32 ± 18 vs. 75 ± 29%) were less in participants with ESRD despite exercise being performed at a higher percentage of maximum minute ventilation (48 ± 3% vs. 39 ± 3%) and heart rate (82 ± 2 vs. 64 ± 2%). Ventilatory and chronotropic incompetence contribute to exercise intolerance in individuals with ESRD. Both are potential targets for medical and lifestyle interventions.

Bronchodilation Increases Estimated Ventilatory Capacity In Children With Mild Asthma

PURPOSE: Children with asthma experience reduced maximal expiratory flows, which can decrease ventilatory capacity and increase ventilatory limitations during exercise; however, the effects of mid-flow bronchodilation on these variables are underappreciated. The purpose of this study was to examine the effect of bronchodilation on ventilatory capacity and ventilatory limitations during a maximal exercise test. METHODS: Nine children with mild asthma (7 boys, 10±1 yr, BMI percentile: 66±30, forced expiratory volume in 1s, FEV1: 106±24 %predicted, Range 78-144) completed spirometry before and after 360μg of albuterol. On a separate visit, they completed an incremental exercise test to exhaustion. Estimated ventilatory capacity was calculated using the volume time curve from estimated maximal tidal volume (FVC/2) and estimated maximal total respiratory cycle time (2×FET25-75%) both before and after bronchodilator. Ventilatory limitation was defined as <10% of breathing reserve (Estimated ventilatory capacity - maximum minute ventilation). RESULTS: Estimated ventilatory capacity increased by 16% after bronchodilator (60±23 vs. 69±27 L/min; p=0.013). Measured maximal tidal volume was lower than estimated (1.12±0.32 vs. 1.33±0.25, p=0.002) but measured maximal total respiratory cycle time (TTot) was not different from estimated (1.41±0.36 vs. 1.47±0.46, p=0.792). In a subset of seven children who received 180μg albuterol before the incremental test, five would have been ventilatory limited (i.e., <10%breathing reserve) at maximal exercise using “before bronchodilator” estimated ventilatory capacity (breathing reserve range: -61 to +9%). However, only one child was ventilatory limited at maximal exercise using “after bronchodilator” estimated ventilatory capacity. CONCLUSIONS: Bronchodilator administration prior to maximal exercise testing may be necessary to increase estimated ventilatory capacity and reduce ventilatory limitations even in children with mild asthma.

A Focused Review on the Maximal Exercise Responses in Hypo- and Normobaric Hypoxia: Divergent Oxygen Uptake and Ventilation Responses.

The literature suggests that acute hypobaric (HH) and normobaric (NH) hypoxia exposure elicits different physiological responses. Only limited information is available on whether maximal cardiorespiratory exercise test outcomes, performed on either the treadmill or the cycle ergometer, are affected differently by NH and HH. A focused literature review was performed to identify relevant studies reporting cardiorespiratory responses in well-trained male athletes (individuals with a maximal oxygen uptake, VO2max > 50 mL/min/kg at sea level) to cycling or treadmill running in simulated acute HH or NH. Twenty-one studies were selected. The exercise tests in these studies were performed in HH (n = 90) or NH (n = 151) conditions, on a bicycle ergometer (n = 178) or on a treadmill (n = 63). Altitudes (simulated and terrestrial) varied between 2182 and 5400 m. Analyses (based on weighted group means) revealed that the decline in VO2max per 1000 m gain in altitude was more pronounced in acute NH vs. HH (−7.0 ± 1.4% vs. −5.6 ± 0.9%). Maximal minute ventilation (VEmax) increased in acute HH but decreased in NH with increasing simulated altitude (+1.9 ± 0.9% vs. −1.4 ± 1.8% per 1000 m gain in altitude). Treadmill running in HH caused larger decreases in arterial oxygen saturation and heart rate than ergometer cycling in acute HH, which was not the case in NH. These results indicate distinct differences between maximal cardiorespiratory responses to cycling and treadmill running in acute NH or HH. Such differences should be considered when interpreting exercise test results and/or monitoring athletic training.

Dynamic Warm-up Effects On Maximal Treadmill Exercise Performance In Children: A Pilot Study

Dynamic warm-up protocols (DWP) consisting of moderate- and high-intensity exercise movements have been found to enhance strength and power performance in youth; however, the effects of DWP on maximal treadmill exercise performance in children are unclear. Prior to pediatric exercise testing participants typically perform low-intensity treadmill walking (TW). PURPOSE: To compare the effects of a DWP with a TW warm-up protocol on maximal exercise performance in children. METHODS: 11 healthy children (10.8 ± 1.5 vrs) were tested for peak oxygen uptake (VO2 peak) on 2 nonconsecutive days following different 6 min warm-up protocols performed in random order. DWP consisted of 9 progressive body weight movements including dynamic stretches, lunges, hip bridges, and jumps whereas the TW protocol consisted of walking on a motor-driven treadmill at 2.2 mph and 0% grade. Comparisons between trials were made with a paired t-test. RESULTS: VO2 peak was significantly higher (p=0.04) following DWP than TW (56.9 ± 9.1 vs 52.7 ± 9.4 ml/kg/min) and a trend (p=0.08) towards greater maximal heart rate was noted following DWP vs TW (192.5 ± 7.5 vs 190.9 ± 7.1 bpm, respectively). No significant differences between DWP and TW trials were observed for maximal minute ventilation (70.7 ± 17.5 vs 64.0 ± 10.4 L/min, respectively), maximal respiratory exchange ratio (1.08 ± 0.05 vs 1.08 ± 0.07, respectively) and total exercise test time (640.9 ± 77.8 vs 638.0 ± 97.4 sec, respectively). No order effects between test day 1 and test day 2 were observed for any variable. CONCLUSIONS: These findings indicate that the design of the warm-up protocol can influence the cardiopulmonary responses to maximal treadmill exercise and that a DWP can result in a higher VO2 peak than a low intensity TW protocol in healthy children.