Differential Effects of Exercise Intensity and Tolerable Duration on Exercise-Induced Diaphragm and Expiratory Muscle Fatigue.

We investigated the effect of exercise intensity and tolerable duration on the development of exercise-induced diaphragm and expiratory muscle fatigue. Ten healthy adults (25 ± 5 y; 2 females) cycled to intolerance on three separate occasions: 1) 5% below critical power ( 0.05). In conclusion, the magnitude of exercise-induced diaphragm fatigue was greater after longer duration severe exercise than after shorter duration severe and heavy exercise. By contrast, the magnitude of exercise-induced expiratory muscle fatigue was unaffected by exercise intensity and tolerable duration.

Effect of Ultra-Marathon Trail Running at Sea Level and Altitude on Alveolar-Capillary Function and Lung Diffusion.

INTRODUCTION: Endurance exercise at altitude can increase cardiac output and pulmonary vascular pressure to levels that may exceed the stress-tolerability of the alveolar-capillary unit. This study examined the effect of ultra-marathon trail racing at different altitudes (ranging from <1000 m to between 1500 - 2700 m) on alveolar-capillary recruitment and lung diffusion. METHODS: Cardiac and lung function were examined before and after an ultra-marathon in 67 runners (age:41 ± 9y, BMI:23 ± 2 kg/m2, 10 females), and following 12-24 h of recovery in a subset (n = 27). Cardiac biomarkers (cTnI & BNP) were assessed from whole blood, while lung fluid accumulation (comet tails), stroke volume (SV) and cardiac output (Q) were quantified via echocardiography. Lung diffusing capacity for carbon monoxide (DLco) and its components, alveolar membrane conductance (Dm) and capillary blood volume (Vc), were determined via a single-breath method at rest and during three stages of submaximal semi-recumbent cycling (20, 30, & 40 W). RESULTS: Average race time was 25 ± 12 h. From pre- to post-race, there was an increase in cardiac biomarkers (cTnI: 0.04 ± .02 vs 0.13 ± .03 ng/ml; BNP: 20 ± 2 vs 112 ± 21 pg/ml, p < 0.01) and lung comet tails (2 ± 1 vs 7 ± 6, p < 0.01), a decrease in resting and exercise SV (76 ± 2 vs 69 ± 2 ml; 40 W: 93 ± 2 vs 88 ± 2 ml, p < 0.01), and an elevation in Q at rest (4.1 ± 0.1 vs 4.6 ± 0.2 l/min, p < 0.01; 40 W: 7.3 ± 0.2 vs 7.4 ± 0.3 l/min, p = 0.899). Resting DLco and Vc decreased after the race (p < 0.01), while Dm was unchanged (p = 0.465); however, during the three stages of exercise DLco, Vc and Dm were all reduced from pre- to post-race (40 W: 36.3 ± 0.9 vs 33.0 ± 0.8 mL/min/mmHg; 83 ± 3 vs 73 ± 2 mL; 186 ± 6 vs 170 ± 7 mL/min/mmHg, respectively, p < 0.01). When corrected for alveolar volume and Q, DLco decreased from pre- to post-race (p < 0.01), and changes in DLco were similar for all ultra-marathon events (p > 0.05). CONCLUSIONS: Competing in an ultra-marathon leads to a transient increase in cardiac injury biomarkers, mild lung-fluid accumulation, and impairments in lung diffusion. Reductions in DLco are predominantly caused by a reduced Vc and possible pulmonary capillary de-recruitment at rest. However, impairments in alveolar-capillary recruitment and Dm both contribute to a fall in exertional DLco following an ultra-marathon. Perturbations in lung diffusion were evident across a range of event distances and varying environmental exposures.

Does COVID-19 impair V̇o2peak in patients with cardiorespiratory disease? Insight from cardiopulmonary responses to maximal exercise pre- and post-illness.

Reduced exercise capacity has been suggested as a cardinal sequela of COVID-19. However, only cross-sectional approaches that either do not consider individuals with concomitant cardiorespiratory disease or account for exercise capacity before infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) support this assumption. Is reduced exercise capacity a sequela of SARS-CoV-2 infection in patients with concomitant cardiorespiratory disease? We retrospectively reviewed cardiopulmonary exercise testing (CPET) data collected across three hospitals between October 2018 and March 2022. Forty-two patients who completed a CPET before and after COVID-19 and 25 patients who performed two separate CPETs but did not contract COVID-19 (CTL) were included. Within each patient, the same test protocol was performed at the first and second CPETs. The time between CPETs was similar between the groups (COVID-19 489 ± 534 vs. CTL 534 ± 257 days, P = 0.662). The COVID-19 group performed the CPETs 312 ± 232 days before and 176 ± 110 days after infection. Exercise time, peak heart rate, peak systolic pressure, oxygen uptake (V̇o2) at anaerobic threshold, peak ventilation, and ventilatory efficiency were not different between the CPETs in both groups. Peak V̇o2 was reduced from before to after SARS-CoV-2 infection. However, the change in V̇o2peak from the first to the second CPET was not different between COVID-19 vs. CTL. Accounting for V̇o2peak before COVID-19 and including a group of control patients, we find limited evidence for reduced exercise capacity as a sequela of SARS-CoV-2 infection in patients with concomitant cardiorespiratory disease.NEW & NOTEWORTHY There is accumulating evidence that reduced exercise capacity is, or can be, an outcome following COVID-19. However, evidence to date relies upon cross-sectional approaches that either do not consider patients with concomitant cardiorespiratory disease or account for pre-infection exercise capacity data. Accounting for V̇o2peak before COVID-19 and including a group of control patients, we find limited evidence for reduced exercise capacity as a sequela of SARS-CoV-2 infection in patients with concomitant cardiorespiratory disease.

Lung "Comet Tails" in Healthy Individuals: Accumulation or Clearance of Extravascular Lung Water?

Parks, Jordan K, Courtney M. Wheatley-Guy, Glenn M. Stewart, Caitlin C. Fermoyle, Bryan J. Taylor, Jesse Schwartz, Briana Ziegler, Kay Johnson, Alice Gavet, Loïc Chabridon, Paul Robach, and Bruce D. Johnson. Lung "Comet Tails" in healthy individuals: accumulation or clearance of extravascular lung water? High Alt Med Biol. 24:230-233, 2023-Ultrasound lung comet tails (or B-lines) tend to be limited in number (<5) or absent under ultrasound examination, and the appearance of diffuse B-lines with lung sliding has been suggested to identify pulmonary edema. Clinical evaluation of B-lines has been utilized as a bedside test to assess pulmonary congestion in patients with heart failure. Exposure to altitude or prolonged exercise can alter fluid regulation and can lead to pulmonary congestion or edema. As such, B-lines have been utilized in the field to monitor for pathological lung fluid accumulation. However, ultrasound lung comet lines might not be as reliable for identifying extravascular lung water (EVLW) as previously thought in healthy individuals exercising at altitude where an increase in the number of ultrasound lung comets would reflect fluid buildup in the interstitial space of the alveoli and pulmonary capillaries. This report will focus on reviewing the literature and our data from a group of ultraendurance runners that completed the Ultra Trail Mont Blanc race that demonstrates that lung comet tails may not always be evidence of pathological fluid accumulation in healthy individuals and as such should be used to assess EVLW in concert with other diagnostic testing.

Pneumatic stenting in the surgical candidacy assessment for cough variant expiratory central airway collapse.

Expiratory Central Airway Collapse (ECAC) is a multifactorial, underdiagnosed entity that poses unique challenges. Airway stenting is used as a predictor for successful outcomes after central airway stabilization surgery via tracheobronchoplasty (TBP). This approach may pose suboptimal performance in certain ECAC variants. We hypothesize that Continuous Positive Airway Pressure (CPAP), used as a pneumatic stent, could be a non-invasive alternative to evaluate surgical candidacy in cough-predominant ECAC presentations. We report on a 67-year-old female with a history of chronic cough and confirmed ECAC. After optimization of medical therapy without significant relief and unsuccessful stent trial. We opted to perform CPAP trial during exercise, the patient exercised on a treadmill, and CPAP was applied at two levels (9 cmH2O, 11 cmH2O). The use of CPAP was associated with resolution of cough and a decrease in exercise-related perceived exertion. Applying CPAP during exercise may be a promising alternative to stent trials to determine patients' candidacy for surgical management of cough-predominant ECAC.

Pulmonary Capillary Recruitment Is Attenuated Post Left Ventricular Assist Device Implantation.

There is limited knowledge of pulmonary physiology and pulmonary function after continuous flow-left ventricular assist device (CF-LVAD) implantation. Therefore, this study investigated whether CF-LVAD influenced pulmonary circulation by assessing pulmonary capillary blood volume and alveolar-capillary conductance in addition to pulmonary function in patients with heart failure. Seventeen patients with severe heart failure who were scheduled for CF-LVAD implantation (HeartMate II, III, Abbott, Abbott Park, IL or Heart Ware, Medtronic, Minneapolis, MN) participated in the study. They underwent pulmonary function testing (measures of lung volumes and flow rates) and unique measures of pulmonary physiology using a rebreathe technique that quantified the diffusing capacity of the lungs for carbon monoxide (DLCO) and diffusing capacity of the lungs for nitric oxide before and 3 months after CF-LVAD implantation. After CF-LVAD, pulmonary function was not significantly changed (p >0.05). For lung diffusing capacity, alveolar volume (VA) was not changed (p = 0.47), but DLCO was significantly reduced (p = 0.04). After correcting for VA, DLCO/VA showed a trend toward reduction (p = 0.08). For the alveolar-capillary component, capillary blood volume (Vc) was significantly reduced (p = 0.04), and alveolar-capillary membrane conductance trended toward a reduction (p = 0.06). However, alveolar-capillary membrane conductance/Vc was not altered (p = 0.92). In conclusion, soon after CF-LVAD implantation, Vc is reduced likely because of pulmonary capillary derecruitment, which contributes to the decrease in lung diffusing capacity.

Sex-Specific Physiological Responses to Ultramarathon.

PURPOSE: Despite a growing body of literature on the physiological responses to ultramarathon, there is a paucity of data in females. This study assessed the female physiological response to ultramarathon and compared the frequency of perturbations to a group of race- and time-matched males. METHODS: Data were collected from 53 contestants of an ultramarathon trail race at the Ultra-Trail du Mont-Blanc (UTMB®) in 2018/19. Before and within 2 h of the finish, participants underwent physiological assessments, including blood sampling for biomarkers (creatine kinase-MB isoenzyme [CK-MB], cardiac troponin I [cTnI], brain natriuretic peptide [BNP], and creatinine [Cr]), pulmonary function testing (spirometry, exhaled NO, diffusing capacities, and mouth pressures), and transthoracic ultrasound (lung comet tails, cardiac function). Data from eight female finishers (age = 36.6 ± 6.9 yr; finish time = 30:57 ± 11:36 h:min) were compared with a group of eight time-matched males (age = 40.3 ± 8.3 yr; finish time = 30:46 ± 10:32 h:min). RESULTS: Females exhibited significant pre- to postrace increases in BNP (25.8 ± 14.6 vs 140.9 ± 102.7 pg·mL -1 ; P = 0.007) and CK-MB (3.3 ± 2.4 vs 74.6 ± 49.6 IU·L -1 ; P = 0.005), whereas males exhibited significant pre- to postrace increases in BNP (26.6 ± 17.5 vs 96.4 ± 51.9 pg·mL -1 ; P = 0.002), CK-MB (7.2 ± 3.9 vs 108.8 ± 37.4 IU·L -1 ; P = 0.002), and Cr (1.06 ± 0.19 vs 1.23 ± 0.24 mg·dL -1 ; P = 0.028). Lung function declined in both groups, but males exhibited additional reductions in lung diffusing capacities (DL CO = 34.4 ± 5.7 vs 29.2 ± 6.9 mL⋅min -1 ⋅mm Hg -1 , P = 0.004; DL NO = 179.1 ± 26.2 vs 152.8 ± 33.4 mL⋅min -1 ⋅mm Hg -1 , P = 0.002) and pulmonary capillary blood volumes (77.4 ± 16.7 vs 57.3 ± 16.1 mL; P = 0.002). Males, but not females, exhibited evidence of mild postrace pulmonary edema. Pooled effect sizes for within-group pre- to postrace changes, for all variables, were generally larger in males versus females ( d = 0.86 vs 0.63). CONCLUSIONS: Ultramarathon negatively affects a range of physiological functions but generally evokes more frequent perturbations, with larger effect sizes, in males compared to females with similar race performances.

Inspiratory muscle weakness in cardiovascular diseases: Implications for cardiac rehabilitation.

Exercise limitation is a cardinal manifestation of many cardiovascular diseases (CVD) and is associated with poor prognosis. It is increasingly well understood that exercise-based cardiac rehabilitation (CR) is an intervention that portends favorable clinical outcomes, including improvements in exercise capacity. The etiology of exercise limitation in CVD is multifactorial but is typically governed by terminal sensations of pain, fatigue, and/or breathlessness. A known but perhaps underestimated complication of CVD that contributes to breathlessness and exercise intolerance in such patients is inspiratory muscle dysfunction. For example, inspiratory muscle dysfunction, which encompasses a loss in muscle mass and/or pressure generating capacity, occurs in up to ~40% of patients with chronic heart failure and is associated with breathlessness, exertional intolerance, and worse survival in this patient population. In this review, we define inspiratory muscle weakness, detail its prevalence in a range of CVDs, and discuss how inspiratory weakness impacts physiological function and clinical outcomes in patients with CVD often referred to CR. We also evaluate the available evidence addressing the effects of exercise-based CR with and without concurrent specific inspiratory muscle training (IMT) on inspiratory muscle function, general physiological function, and clinical outcomes in patients with CVD. Finally, we consider whether the assessment of global respiratory muscle function should become standard as part of the patient intake assessment for phase II CR programs, giving practical guidance on the implementation of such measures as well as IMT as part of phase II CR.

Cardiac structure and function in elite female athletes: A systematic review and meta-analysis.

We conducted a meta-analysis to synthesize the best available evidence comparing cardiac biventricular structure and function using cardiac magnetic resonance imaging (CMR) and transthoracic echocardiography (TTE) in elite female athletes and healthy controls (HC). Chronic exposure to exercise may induce cardiac chamber enlargement as a means to augment stroke volume, a condition known as the "athlete's heart." These changes have not been clearly characterized in female athletes. Multiple databases were searched from inception to June 18, 2019. Outcomes of interest included left ventricular (LV) and right ventricular (RV) dimensional, volumetric, mass, and functional assessments in female athletes. Most values were indexed to body surface area. The final search yielded 22 studies, including 1000 female athletes from endurance, strength, and mixed athletic disciplines. CMR-derived LV end-diastolic volume (LVEDV) and RV end-diastolic volume (RVEDV) were greater in endurance athletes (EA) versus HC (17.0% and 18.5%, respectively; both p < 0.001). Similarly, TTE-derived LVEDV and RVEDV were greater in EA versus HC (16.8% and 28.0%, respectively; both p < 0.001). Both LVEF and RVEF were lower in EA versus HC, with the most pronounced difference observed in RVEF via TTE (9%) (p < 0.001). LV stroke volume was greater in EA versus HC via both CMR (18.5%) and TTE (13.2%) (both p < 0.05). Few studies reported data for the mixed athlete (MA) population and even fewer studies reported data for strength athletes (SA), therefore a limited analysis was performed on MA and no analysis was performed on SA. This evidence-synthesis review demonstrates the RV may be more susceptible to ventricular enlargement. General changes in LV and RV structure and function in female EA mirrored changes observed in male counterparts. Further studies are needed to determine if potential adverse outcomes occur secondary to these changes.

Facemasks and Walk Distance in Pulmonary Arterial Hypertension Patients.

Little is known about the effect of wearing a facemask on the physiological and perceptual responses to exercise in patients with pulmonary arterial hypertension (PAH). We performed a single-center retrospective study to evaluate whether facemask wearing impacted distanced covered, rating of perceived exertion (RPE), and arterial oxygen saturation (SpO2) during a 6-minute walk test (6MWT) in PAH patients. Forty-five patients being treated for group 1 PAH and who performed a 6MWT before and after implementation of a facemask mandate were included in the analysis. Each included patient performed a 6MWT without (test 1) and with (test 2) a facemask between October 1, 2019, and October 31, 2020. At both time points, all patients also underwent a submaximal cardiopulmonary exercise test, echocardiogram, and blood laboratory tests, with a Registry to Evaluate Early and Long-Term PAH Disease Management Lite 2.0 score calculated. The two 6MWTs were performed 81±51 days apart, and all patients were clinically stable at both testing timepoints. Six-minute walk test distance was not different between test 1 and test 2 (405±108 m vs 400±103 m, P=.81). Similarly, both end-test RPE and lowest SpO2 during the 6MWT were not different in test 1 and test 2 (RPE: 2.5±1.7 vs 2.5±2.1, P=.91; SpO2 nadir: 92.8±3.4% vs 93.3±3.3%, P=.55). Our findings show that wearing a facemask has no discernable impact on the arterial oxygen saturation and perceptual responses to exercise or exercise capacity in patients with moderate-to-severe PAH. This study reinforces the evidence that wearing a facemask is safe in PAH patients, even during exercise.

The Influence of Social Distancing Behaviors and Psychosocial Factors on Physical Activity During the COVID-19 Pandemic: Cross-sectional Survey Study.

BACKGROUND: The COVID-19 pandemic has arguably facilitated a shift toward increased sedentariness and reduced physical activity. Moreover, there is mounting evidence that mental health has also declined during the pandemic. However, it remains unknown to what extent social distancing (SD) behaviors and mental health have affected the physical activity levels of the general population. OBJECTIVE: The purpose of this study was to determine the influence of SD behaviors and prevailing mental health on the odds of being physically active during the early COVID-19 pandemic response. METHODS: A total of 4819 adults (2474/4819, 51.3%, female) from the US population with a median age of 46 (IQR 35-59) completed an online survey during the early pandemic response (April-June 2020). The survey included questions on adherence to 11 SD behaviors, and validated questionnaires which assessed self-reported physical activity, depression, anxiety, and mental well-being. Respondents were categorized into 2 physical activity groups: inactive (0-599 metabolic equivalent of task [MET]-minutes/week) and active (≥600 MET-minutes/week). A logistic generalized additive model (GAM) was used to determine which SD factors and mental health outcomes were associated with physical activity level. RESULTS: The GAM analysis revealed that wearing a facemask in public (odds ratio [OR] 1.46, 95% CI 1.14-1.79; P=.003), limiting the use of public transport (OR 1.47, 95% CI 1.19-1.83; P=.001), and restricting travel outside the house (OR 1.56, 95% CI 1.19-2.05; P=.002) were SD behaviors associated with higher odds of being more physically active. Conversely, avoiding physical activity outside the house was associated with higher odds of being inactive (OR 0.52, 95% CI 0.46-0.63; P<.001). Leaving the house more frequently, and a higher mental well-being were associated with increasing odds of being physically active (P<.001). Engaging with a moderate number of SD behaviors (3-7 total) was positively associated with physical activity, whereas a very high SD vigilance (ie, engaging with ≥10 total behaviors) decreased the odds of being active during the early pandemic response. CONCLUSIONS: Based on the findings of our study, we suggest that future public health messaging of SD guidelines should include (1) a clear portrayal of the benefits of regular exercise on mental health; and (2) a specific focus on how to be physically active outdoors in a COVID-safe manner.

Self-reported physical activity before a COVID-19 'lockdown': is it just a matter of opinion?

There are growing concerns that the COVID-19 pandemic has facilitated a sedentary shift in our physical activity habits. A reduction in physical activity during the pandemic may be secondary to restrictive policies implemented at the government-level, typically those policies which limit interpersonal contact; for example, physical/social distancing. It is without question that social distancing is a necessary measure to mitigate community transmission of the novel virus; however, these policies often limit the public's opportunities to engage in physical activity. The strictest enforcement of social distancing occurs during an authority-mandated 'lockdown' (also known as a 'shelter-in-place' or 'stay-at-home' order). This Viewpoint focuses on the current evidence demonstrating that physical activity declines during a COVID-19 'lockdown'. We highlight the point that most of the available evidence stems from investigations using non-validated, self-reported measures of physical activity and discuss the caveats therewith. This Viewpoint explores whether current evidence reflects an 'actual' or rather a 'perceived' reduction in physical activity, and raises the question of whether this distinction matters in the end.

Characterizing Particulate Generation During Cardiopulmonary Rehabilitation Classes With Patients Wearing Procedural Masks.

BACKGROUND: The clinical benefits of cardiopulmonary rehabilitation are extensive, including improvements in health-related quality of life, emotional condition, physical function, and overall mortality. The COVID-19 pandemic continues to have a negative impact on center-based cardiopulmonary rehabilitation. Justifiable concern exists that the exercise-related increase in pulmonary ventilation within the rehabilitation classes may lead to the generation of infectious respiratory particles. RESEARCH QUESTION: Is cardiopulmonary rehabilitation while wearing a procedural mask a particle-generating procedure? STUDY DESIGN AND METHODS: Data were collected prospectively at a cardiopulmonary rehabilitation facility with all patients wearing a procedural mask. Small (0.3-4.9 µm) and large (5-10 µm) particle generation was quantified using a light-scattering particle counter. Data were analyzed by time, exertion level, and number of participants. RESULTS: A total of 24 distinct patients attended two or more of the cardiopulmonary rehabilitation classes tested. Most of the patients were men (n = 16 [67%]) and were in rehabilitation because of cardiac disease. During the cardiopulmonary rehabilitation class, small and large micrometer-size particles increased with increasing class size. In classes with four patients or more, a significant increase was found from ambient levels in both small (four patients, P < .01; and five patients, P < .01) and large (four patients, P < .01; and five patients, P < .01) particle count that peaked at about 35 to 40 min during each class. INTERPRETATION: Using an airborne particle counter, we found significant exercise-related increases in both small and large micrometer-size particle generation during cardiopulmonary rehabilitation classes, with larger class sizes (ie, more patients), despite participants wearing a procedural mask.

The Effect of Preexercise Expiratory Muscle Loading on Exercise Tolerance in Healthy Men.

PURPOSE: Acute nonfatiguing inspiratory muscle loading transiently increases diaphragm excitability and global inspiratory muscle strength and may improve subsequent exercise performance. We investigated the effect of acute expiratory muscle loading on expiratory muscle function and exercise tolerance in healthy men. METHODS: Ten males cycled at 90% of peak power output to the limit of tolerance (TLIM) after 1) 2 × 30 expiratory efforts against a pressure-threshold load of 40% maximal expiratory gastric pressure (PgaMAX) (EML-EX) and 2) 2 × 30 expiratory efforts against a pressure-threshold load of 10% PgaMAX (SHAM-EX). Changes in expiratory muscle function were assessed by measuring the mouth pressure (PEMAX) and PgaMAX responses to maximal expulsive efforts and magnetically evoked (1 Hz) gastric twitch pressure (Pgatw). RESULTS: Expiratory loading at 40% of PgaMAX increased PEMAX (10% ± 5%, P = 0.001) and PgaMAX (9% ± 5%, P = 0.004). Conversely, there was no change in PEMAX (166 ± 40 vs 165 ± 35 cm H2O, P = 1.000) or PgaMAX (196 ± 38 vs 192 ± 39 cm H2O, P = 0.215) from before to after expiratory loading at 10% of PgaMAX. Exercise time was not different in EML-EX versus SHAM-EX (7.91 ± 1.96 vs 8.09 ± 1.77 min, 95% CI = -1.02 to 0.67, P = 0.651). Similarly, exercise-induced expiratory muscle fatigue was not different in EML-EX versus SHAM-EX (-28% ± 12% vs -26% ± 7% reduction in Pgatw amplitude, P = 0.280). Perceptual ratings of dyspnea and leg discomfort were not different during EML-EX versus SHAM-EX. CONCLUSION: Acute expiratory muscle loading enhances expiratory muscle function but does not improve subsequent severe-intensity exercise tolerance in healthy men.

The cardiovascular consequences of fatiguing expiratory muscle work in otherwise resting healthy humans.

In 11 healthy adults (25 ± 4 yr; 2 female, 9 male subjects), we investigated the effect of expiratory resistive loaded breathing [65% maximal expiratory mouth pressure (MEP), 15 breaths·min-1, duty cycle 0.5; ERLPm] on mean arterial pressure (MAP), leg vascular resistance (LVR), and leg blood flow ([Formula: see text]). On a separate day, a subset of five male subjects performed ERL targeting 65% of maximal expiratory gastric pressure (ERLPga). ERL-induced expiratory muscle fatigue was confirmed by a 17 ± 5% reduction in MEP (P < 0.05) and a 16 ± 12% reduction in the gastric twitch pressure response to magnetic nerve stimulation (P = 0.09) from before to after ERLPm and ERLPga, respectively. From rest to task failure in ERLPm and ERLPga, MAP increased (ERLPm = 31 ± 10 mmHg, ERLPga = 18 ± 9 mmHg, both P < 0.05), but group mean LVR and [Formula: see text] were unchanged (ERLPm: LVR = 0.78 ± 0.21 vs. 0.97 ± 0.36 mmHg·mL-1·min, [Formula: see text] = 133 ± 34 vs. 152 ± 74 mL·min-1; ERLPga: LVR = 0.70 ± 0.21 vs. 0.84 ± 0.33 mmHg·mL-1·min, [Formula: see text] = 160 ± 48 vs. 179 ± 110 mL·min-1) (all P ≥ 0.05). Interestingly, [Formula: see text] during ERLPga oscillated within each breath, increasing (∼66%) and decreasing (∼50%) relative to resting values during resisted expirations and unresisted inspirations, respectively. In conclusion, fatiguing expiratory muscle work did not affect group mean LVR or [Formula: see text] in otherwise resting humans. We speculate that any sympathetically mediated peripheral vasoconstriction was counteracted by transient mechanical effects of high intra-abdominal pressures during ERL.NEW & NOTEWORTHY Fatiguing expiratory muscle work in otherwise resting humans elicits an increase in sympathetic motor outflow; whether limb blood flow ([Formula: see text]) and leg vascular resistance (LVR) are affected remains unknown. We found that fatiguing expiratory resistive loaded breathing (ERL) did not affect group mean [Formula: see text] or LVR. However, within-breath oscillations in [Formula: see text] may reflect a sympathetically mediated vasoconstriction that was counteracted by transient increases in [Formula: see text] due to the mechanical effects of high intra-abdominal pressure during ERL.

Exercise intolerance in heart failure: The important role of pulmonary hypertension.

NEW FINDINGS: What is the topic of this review? This review concerns the negative impact of pulmonary hypertension (PH) on the pulmonary haemodynamic and gas exchange responses to exercise, considering the mechanisms by which PH plays a role in exercise intolerance in heart failure (HF) patients. What advances does it highlight? The hallmark limited pulmonary vascular 'reserve' and impaired pulmonary gas exchange responses to exercise in HF are worsened by the development of PH; these are key determinants of exercise intolerance. Even HF patients who present with 'normal' pulmonary vascular function experience exercise-induced PH, which plays a role in exercise intolerance. ABSTRACT: Patients with heart failure universally complain of exertional intolerance, but the underlying cause(s) of this intolerance may differ between patients with different disease phenotypes. Exercise introduces an impressive stress to the lungs, where elevations in venous return and cardiac output engender substantial increases in pulmonary blood volume and flow. Relative to healthy individuals, the pulmonary vascular reserve to accept this increase in pulmonary perfusion is compromised in heart failure, with a growing body of evidence suggesting that the development of pulmonary hypertension (PH), and in particular a precapillary component of PH, worsens the pulmonary haemodynamic response to exercise in these patients. Characterized by an exaggerated increase in pulmonary arterial pressure and an elevation in pulmonary vascular resistance, this dysfunctional pulmonary haemodynamic response plays a role in exercise intolerance, probably through an impairment of right ventricular function, underperfusion of the pulmonary circulation and a subsequent reduction in systemic blood flow and oxygen delivery. The hallmark abnormalities in ventilatory and pulmonary gas exchange that accompany heart failure, including a greater ventilatory equivalent for carbon dioxide, are also worsened by the development of PH. This raises the possibility that measures of exercise pulmonary gas exchange might help to 'describe' underlying PH in heart failure; however, several fundamental issues and questions need to be addressed before such gas exchange measures could truly be considered efficacious measures used to differentiate the type of PH and track the severity of PH in heart failure. exercise intolerance, heart failure, pulmonary gas exchange, pulmonary haemodynamics, pulmonary hypertension.

Exercise Intolerance in Heart Failure: Central Role for the Pulmonary System.

We propose that abnormalities of the pulmonary system contribute significantly to the exertional dyspnea and exercise intolerance observed in patients with chronic heart failure. Interventions designed to address the deleterious pulmonary manifestations of heart failure may, therefore, yield promising improvements in exercise tolerance in this population.

Pulmonary and respiratory muscle function in response to 10 marathons in 10 days.

PURPOSE: Marathon and ultramarathon provoke respiratory muscle fatigue and pulmonary dysfunction; nevertheless, it is unknown how the respiratory system responds to multiple, consecutive days of endurance exercise. METHODS: Nine trained individuals (six male) contested 10 marathons in 10 consecutive days. Respiratory muscle strength (maximum static inspiratory and expiratory mouth-pressures), pulmonary function (spirometry), perceptual ratings of respiratory muscle soreness (Visual Analogue Scale), breathlessness (dyspnea, modified Borg CR10 scale), and symptoms of Upper Respiratory Tract Infection (URTI), were assessed before and after marathons on days 1, 4, 7, and 10. RESULTS: Group mean time for 10 marathons was 276 ± 35 min. Relative to pre-challenge baseline (159 ± 32 cmH2O), MEP was reduced after day 1 (136 ± 31 cmH2O, p = 0.017), day 7 (138 ± 42 cmH2O, p = 0.035), and day 10 (130 ± 41 cmH2O, p = 0.008). There was no change in pre-marathon MEP across days 1, 4, 7, or 10 (p > 0.05). Pre-marathon forced vital capacity was significantly diminished at day 4 (4.74 ± 1.09 versus 4.56 ± 1.09 L, p = 0.035), remaining below baseline at day 7 (p = 0.045) and day 10 (p = 0.015). There were no changes in FEV1, FEV1/FVC, PEF, MIP, or respiratory perceptions during the course of the challenge (p > 0.05). In the 15-day post-challenge period, 5/9 (56%) runners reported symptoms of URTI, relative to 1/9 (11%) pre-challenge. CONCLUSIONS: Single-stage marathon provokes acute expiratory muscle fatigue which may have implications for health and/or performance, but 10 consecutive days of marathon running does not elicit cumulative (chronic) changes in respiratory function or perceptions of dyspnea. These data allude to the robustness of the healthy respiratory system.