Work Rate Test Research Articles

Proportional Assist Ventilation Improves Leg Muscle Reoxygenation After Exercise in Heart Failure With Reduced Ejection Fraction.

BackgroundRespiratory muscle unloading through proportional assist ventilation (PAV) may enhance leg oxygen delivery, thereby speeding off-exercise oxygen uptake () kinetics in patients with heart failure with reduced left ventricular ejection fraction (HFrEF).MethodsTen male patients (HFrEF = 26 ± 9%, age 50 ± 13 years, and body mass index 25 ± 3 kg m2) underwent two constant work rate tests at 80% peak of maximal cardiopulmonary exercise test to tolerance under PAV and sham ventilation. Post-exercise kinetics of , vastus lateralis deoxyhemoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy, and cardiac output (QT) by impedance cardiography were assessed.ResultsPAV prolonged exercise tolerance compared with sham (587 ± 390 s vs. 444 ± 296 s, respectively; p = 0.01). PAV significantly accelerated recovery (τ = 56 ± 22 s vs. 77 ± 42 s; p < 0.05), being associated with a faster decline in Δ[deoxy-Hb + Mb] and QT compared with sham (τ = 31 ± 19 s vs. 42 ± 22 s and 39 ± 22 s vs. 78 ± 46 s, p < 0.05). Faster off-exercise decrease in QT with PAV was related to longer exercise duration (r = −0.76; p < 0.05).ConclusionPAV accelerates the recovery of central hemodynamics and muscle oxygenation in HFrEF. These beneficial effects might prove useful to improve the tolerance to repeated exercise during cardiac rehabilitation.

Ramp vs. step tests: valid alternatives to determine the maximal lactate steady-state intensity?

The aims of this study were (1) to investigate if the respiratory compensation point (RCP) as derived from ramp incremental (RI) exercise could accurately predict the power output (PO) at the maximal lactate steady state (MLSS), and (2) to compare its accuracy with the second lactate threshold (LT2) obtained from step incremental (SI) exercise. Nineteen participants performed a RI test (30W·min-1) to determine RCP, a SI test (30 or 40W·3min-1) to determine LT2, and two or more constant work rate (CWR) tests to determine MLSS. For each participant, the [Formula: see text]O2/PO relationship for RI and CWR exercise was established. The ramp-identified PO at RCP was corrected by accounting for the gap between these relationships using the individually determined [Formula: see text] O2/PO regression above GET (RCPcorr-1) or usinga fixed regression slope (RCPcorr-2). LT2 was determined using four methods: Dmax, modified Dmax (ModDmax), 4-mM threshold (LT4mM) and an expert-determined LT2 (LT2-expert). RCPcorr-1 (235 ± 69W), RCPcorr-2 (228 ± 58W) and LT2-expert (227 ± 61W) were not different from MLSS (225 ± 60W). Dmax (203 ± 53W) underestimated MLSS, while RCP (280 ± 60W), ModDmax (235 ± 67W) and LT4mM (234 ± 68W) overestimated MLSS. The [Formula: see text]O2 at RCP (3.13 ± 0.79L·min-1) and LT2-expert (2.99 ± 0.19L·min-1) did not differ from MLSS (3.05 ± 0.72L·min-1). This study demonstrated that RCP as derived from RI exercise and LT2 as derived from SI exercise can be equally accurate to determine the PO associated with MLSS. Although these results confirmed the suitability of RI and SI tests for this purpose, they also highlighted the importance of an appropriate threshold method selection and the eye of the expert.

Physiological Changes Differ between Responders and Nonresponders to Pulmonary Rehabilitation in COPD.

Not all patients with chronic obstructive pulmonary disease (COPD) experience similar benefits after pulmonary rehabilitation (PR). This pre-post PR study used a large sample of patients with COPD to determine whether PR-induced changes of oxygen uptake (V˙O2) kinetics and exercise responses of V˙O2, carbon dioxide output (V˙CO2), minute ventilation (V˙E), V˙E/V˙CO2, breathing frequency, and tidal volume differed between responders and nonresponders to PR. Responders to PR were defined as patients with a minimal clinically important increase in endurance time of 105 s. Isotime (=180 s) values of V˙O2, V˙CO2, V˙E, V˙E/V˙CO2, breathing frequency, and tidal volume; gains of V˙O2, V˙CO2, and V˙E; and V˙O2 mean response time of 183 patients with COPD (forced expiratory volume in 1 s: 56% ± 19% predicted) were compared between pre- and post-PR constant work rate tests. After PR, only the group of responders significantly decreased V˙O2 mean response time (P < 0.05), V˙CO2 gain, V˙E gain, and isotime values of V˙CO2, V˙E, and V˙E/V˙CO2 (all, P < 0.001), while also improving their breathing pattern (e.g., decreased breathing frequency isotime value; P < 0.0001). These changes were not observed in the group of nonresponders. Changes in physiological exercise responses were correlated with changes in physical performance (e.g., correlation between changes in V˙O2 mean response time and endurance time: P = 0.0002, r = -0.32). PR-induced changes in physiological exercise responses differed between responders and nonresponders. Physiological changes are relevant to explain the variable improvements of physical performance after PR in patients with COPD.

Effect of normobaric hypoxic exercise on blood pressure in old individuals

PurposeTo test the hypothesis that the combination of endurance training and hypoxia leads to greater improvements in resting and exercise blood pressure in old sedentary individuals compared to endurance training only.MethodsWe randomly assigned 29 old overweight participants (age: 62 ± 6 years, body mass index (BMI): 28.5 ± 0.5 kg/m2, 52% men) to single blind 8-week bicycle exercise in hypoxia (fraction of inspired oxygen (FIO2) = 0.15) or normoxia (FIO2 = 0.21). Brachial blood pressure was measured at rest, during maximal incremental exercise testing, and during a 30 min constant work rate test, at baseline and after the training period.ResultsWork rate, heart rate and perceived exertion during training were similar in both groups, with lower oxygen saturation for participants exercising under hypoxia (88.7 ± 1.5 vs. 96.2 ± 1.2%, t(27) = − 13.04, p < 0.001, |g|= 4.85). Office blood pressure and blood pressure during incremental exercise tests did not change significantly in either group after the training program. Systolic blood pressure during the constant work rate test was reduced after training in hypoxia (160 ± 18 vs. 151 ± 14 mmHg, t(13) = 2.44 p < 0.05, |d|= 0.55) but not normoxia (154 ± 22 vs. 150 ± 16 mmHg, t(14) = 0.75, p = 0.46, |d|= 0.18) with no difference between groups over time (F = 0.08, p = 0.77, η2 = 0.01).ConclusionIn old individuals hypoxia in addition to exercise does not have superior effects on office or exercise blood pressure compared to training in normoxia.Trial registration numberClinicalTrials.gov No. NCT02196623 (registered 22 July 2014).

Role of Respiratory Buffering in the Relationship Between Recovery and Performance Fatigability Following Aerobic Exercise Training: A Longitudinal, Observational, Pilot Study.

Purpose: This study characterized the influence of excess expired carbon dioxide (excess V̇co 2) in the relationship between recovery and fatigability. Methods: Twenty healthy adults completed peak cardiopulmonary exercise tests (CPXs) and constant work rate tests before and after a vigorous, 4-week aerobic exercise training (AET) regimen. Each test was followed by 10 minutes of recovery and an endurance test at 70% of peak watts attained during CPX. Fatigability was assessed by measures of time to exhaustion and power output. Metabolic and recovery capacity indices were obtained. Data were analyzed using correlations and regressions and compared pre/post AET using paired t tests. Results: Significant improvements in recovery and fatigability were observed after AET, along with significant increases in total and excess V̇co 2. Relationships between measures of recovery and fatigability were observed, although strengths of the relationships were diminished after controlling analyses for the effect of excess V̇co 2. Conclusions: This study suggests that the ionic buffering capacity may moderate the relationship between recovery and fatigability. These results could have implications regarding AET-induced buffering dynamics, and its role in fatigue resistance when performing activities above moderate intensities. This may be of particular importance in patients with cardiopulmonary complications, unable to improve peak aerobic capacity.

Inspiratory Muscle Training Potentiates the Beneficial Effects of Proportional Assisted Ventilation on Exertional Dyspnea and Exercise Tolerance in COPD: A Proof-of-Concept Randomized and Controlled Trial

During pulmonary rehabilitation, a subset of subjects with COPD requires adjunct therapy to achieve high-intensity training. Both noninvasive ventilation (NIV) and inspiratory muscle training (IMT) are available to assist these subjects. We aimed to prime the respiratory muscles before NIV with IMT, anticipating additive effects for maximal exercise tolerance (T lim) and dyspnea/leg fatigue relief throughout the exercise as primary outcomes. Changes in the respiratory pattern were secondary outcomes. COPD subjects performed a total of four identical constant work rate tests on a cycle ergometer at 75% of maximum work rate, under control ventilation (SHAM, 4 cm H2O) or proportional assisted ventilation (PAV, individually adjusted), before and after 10 sessions of high-intensity IMT (three times/week) during 30 days. Two-way RM ANOVA with appropriate corrections were performed. Final analysis in nine subjects showed improved T lim (Δ = 111 s) and lower minute-ventilation (Δ = 4 L.min−1) at exhaustion, when comparing the IMT effects within the PAV modality (p = 0.001 and p = 0.036, respectively) and improved T lim for PAV vs. SHAM (PAV main-effect, p = 0.001; IMT main-effect, p = 0.006; PAV vs. IMT interaction, p = 0.034). In addition, IMT + PAV association, compared to PAV alone, resulted in lower respiratory frequency (IMT main-effect, p = 0.009; time main-effect, p < 0.0001; IMT vs. time interaction, p = 0.242) and lower inspiratory time related to duty cycle (IMT main-effect, p = 0.018; time main-effect, p = 0.0001; IMT vs. time interaction, p = 0.004) throughout exercise. The addition of IMT prior to a PAV-supported aerobic bout potentiates exercise tolerance and dyspnea relief and induces favourable changes in ventilatory pattern in severe COPD during high-intensity training (Brazilian Registry of Clinical Trials, number RBR-6n3dzz).

Vitamin B12 Supplementation and NT-proBNP Levels in COPD Patients: A Secondary Analysis of a Randomized and Controlled Study in Rehabilitation.

PurposeThere is evidence of complex interaction between vitamin B12 (vB12) level, hyperhomocysteinemia (HyCy), and natriuretic peptide secretion. Exercise training could also modulate such interaction. In this secondary analysis of a Randomized Clinical Trial performed in a chronic obstructive pulmonary disease (COPD) rehabilitation setting, our primary objective was to investigate the interaction between vB12 supplementation, exercise training, and changes in NT-proBNP levels after 8 weeks of intervention. Secondary objectives were to explore the correlations between acute changes in NT-proBNP levels with (i) acute exercise and (ii) oxygen uptake (V’O2) kinetics during rest-to-exercise transition.MethodsThirty-two subjects with COPD were randomized into four groups: Rehabilitation+vB12 (n = 8), Rehabilitation (n = 8), vB12 (n = 8), or Maltodextrin(n = 8). They were evaluated at baseline and after 8 weeks, during resting and immediately after maximal exercise constant work-rate tests (CWTs, Tlim), for NT-proBNP plasmatic levels.ResultsAfter interaction analysis, the supplementation with vB12 significantly changed the time course of NT-proBNP responses during treatment (p = 0.048). However, the final analysis could not support a significant change in NT-proBNP levels owing to high-intensity constant work-rate exercise (p-value > 0.05). There was a statistically significant correlation between V’O2 time constant and ΔNT-proBNP values (Tlim – rest) at baseline (p = 0.049) and 2 months later (p = 0.015), considering all subjects (n = 32).ConclusionWe conclude that vB12 supplementation could modulate NT-proBNP secretion. Moreover, possibly, the slower the initial V’O2 adjustments toward a steady-state during rest-to-exercise transitions, the more severe the ventricular chamber volume/pressure stress recruitment, expressed through higher NT-proBNP secretion in subjects with larger V’O2 time constants, despite unchanged final acute exercise-induced neurohormone secretion.

Non-metabolic VCO 2, Recovery Off-kinetics, And Performance Fatigability Following Chronic Exercise

PURPOSE: This study characterized the role of non-metabolic expired carbon dioxide (nm-VCO2) in the relationship between recovery and performance fatigability (PF). METHODS: Twenty adults (men, n=9, age=44.7±13.9 years; women, n=11, age=50.3±11.1 years) completed peak cardiopulmonary exercise tests (CPET) and submaximal constant work rate tests (CWRT) on the cycle ergometer on separate days before and after a vigorous, 4-week aerobic exercise training (AET) regimen. Each test was followed by a 10-minute passive recovery and endurance test at 70% of peak watts attained during CPET. PF was indexed by endurance test duration following both peak CPET (End1) and CWRT (End2), peak CPET time (pk-Time) and watts (pk-Watts). Metabolic indices were total VCO2 (tVCO2), metabolic VCO2 (m-VCO2), nm-VCO2, and recovery VO2 and VCO2 off-kinetics response indices (ORI). Data were analyzed using paired t-tests and correlations and compared before and after AET. RESULTS: Significant improvements in recovery and PF measures were observed after AET, along with significant increases in tVCO2 and nm-VCO2. No significant change in m-VCO2 was observed.Relationships between measures of recovery and PF were observed, though the strength of the relationships were diminished (pk-Time, pk-Watts) or became non-significant (End1, End2) after controlling analyses for the effect of nm-VCO2.CONCLUSION: The current study suggests nm-VCO2 may moderate the relationship between recovery and PF and may have implications regarding AET induced buffering dynamics and its role in fatigue resistance during activity above moderate intensities.

Characterization of CO2 Expiration and its Relationship with Performance Fatigability in Adaptation to Chronic Exercise Perturbation

PurposeThis study characterized components of carbon dioxide expiration (VCO2) and their relationship with performance fatigability (PF) in adaptation to chronic exercise perturbation.Methods20 healthy men (n=9, age=44.7±13.9 ) and women (n=11, age=50.3±11.1) completed peak cardiopulmonary exercise (CPET) and constant work rate tests (CWRT) on separate days before and after a vigorous, 4‐week aerobic exercise training (AET) regimen. Each test was followed by 10‐minutes of passive recovery and an endurance test at 70% of the peak watts attainted during the CPET. PF was indexed by the endurance test durations following both the peak CPET (End1) and CWRT (End2), peak CPET time (pk‐Time), and peak CPET watts (pk‐Watts). Metabolic indices were calculated as total VO2 (tVO2), total VCO2 (tVCO2), metabolic VCO2 (m‐VCO2), and non‐metabolic VCO2 (nm‐VCO2). Data were analyzed for significant (p&lt;0.05) changes and determinant relationships using paired t‐tests, and Pearson coefficients of determination (r2).ResultsSignificant reductions (Table ) in PF measures along with significant increases in tVO2, tVCO2, and nm‐VCO2 were observed after AET. A change in m‐VCO2 was not observed. End1 (s) End2 (s) pk‐Time (s) pk‐Watts tVO2 (ml) tVCO2 (ml) m‐VCO2 (ml) nm‐VCO2 (ml) 265±337 p&lt;0.01* 321±392 p&lt;0.01* 63±40 p&lt;0.001* 24±19 p&lt;0.001* 1127±1569 p&lt;0.01* 1512±2225 p&lt;0.01* 904±2255 p=0.089 608±666 p&lt;0.001* nm‐VCO2 was strongly determinant of performance fatigability (pk‐Time r2=0.858, pk‐Watts r2=0.832, end1 r2=0.533, end2 r2=0.682, p&lt;0.001*).ConclusionThe current study demonstrated significant increases in the buffering component of total carbon dioxide expiration but not in the component associated with energy repletion. The buffering component was directly associated with measures of performance, providing plausibility that the buffering component may be a determinant of performance fatigability. End1 (s) End2 (s) pk‐Time (s) pk‐Watts tVO2 (ml) tVCO2 (ml) m‐VCO2 (ml) nm‐VCO2 (ml) 265±337 321±392 63±40 24±19 1127±1569 1512±2225 904±2255 608±666 p&lt;0.01* p&lt;0.01* p&lt;0.001* p&lt;0.001* p&lt;0.01* p&lt;0.01* p=0.089 p&lt;0.001*

Changes in oxygen uptake kinetics after exercise caused by differences in loading pattern and exercise intensity.

AimsThe kinetics of recovery‐period oxygen uptake (VO2) are affected by the O2 deficit generated during exercise. However, studies using ramp tests (RTs) and constant work rate tests (CT) have differently characterized VO2 responses to increased exercise intensity differently. We used these two types of loading patterns to investigate the effects of low‐intensity, medium‐intensity, and high‐intensity exercises on the half time (T1/2) of recovery‐period VO2 and the mechanism.Methods and resultsTen healthy men aged 21.2 ± 0.9 years underwent symptom‐limited cardiopulmonary exercise tests with the ramp protocol to determine their anaerobic threshold. All subjects subsequently underwent three submaximal RT and CT at low, moderate, and high intensities. In all RTs, subjects began exercise by warming up (20 W). In CT, T1/2 was significantly lengthened as exercise intensity increased (CT‐low: 34.0 ± 3.9 s, CT‐moderate: 39.5 ± 3.5 s, CT‐high:44.6 ± 4.2 s; P < 0.01, ANOVA), whereas no significant change was observed in RT, which began with the same work rate (RT‐low: 46.0 ± 5.7 s, RT‐moderate: 45.7 ± 4.8 s, RT‐high: 44.6 ± 3.5 s, RT‐max: 44.8 ± 3.2 s; P = 0.868, ANOVA). Only high‐intensity exercise resulted in two components (the fast and slow components) of VO2 decay, reflecting the increased O2 deficit by anaerobic metabolism.ConclusionsThe exercise intensity at the beginning of an exercise affects early recovery‐period VO2, which is a fast component. The T1/2 of recovery‐period VO2 occurs during the fast component, and an increase in O2 deficit affects both the fast and slow components, lengthening the T1/2. The T1/2 of recovery‐period VO2 in CT at moderate or high intensities, even if not symptom limited, can be used to evaluate exercise intolerance and early occurrence of anaerobic metabolism. Submaximal exercise tests may be considered as convenient methods for evaluating exercise tolerance in patients with cardiac failure.

Kinetic analyses as a tool to examine physiological exercise responses in a large sample of patients with COPD.

Kinetic features such as oxygen uptake (V̇o2) mean response time (MRT), and gains of V̇o2, carbon dioxide output (V̇co2), and minute ventilation (V̇e) can describe physiological exercise responses during a constant work rate test of patients with chronic obstructive pulmonary disease (COPD). This study aimed to establish simple guidelines that can identify COPD patients for whom kinetic analyses are (un)likely to be reliable and examined whether slow V̇o2 responses and gains of V̇o2, V̇co2, and V̇e are associated with ventilatory, cardiovascular, and/or physical impairments. Kinetic features were examined for 265 COPD patients [forced expiratory volume in 1 s (FEV1): 54 ± 19%predicted] who performed a constant work rate test (duration > 180 s) with breath-by-breath measurements of V̇o2, V̇co2, and V̇e. Negative/positive predictive values were used to define cutoff values of relevant clinical variables below/above which kinetic analyses are (un)likely to be reliable. Kinetic feature values were unreliable for 21% (= 56/265) of the patients and for 79% (= 19/24) of the patients with a peak work rate (WRpeak)< 45 W. Kinetic feature values were considered reliable for 94% (= 133/142) of the patients with an FEV1 > 1.3 L. For patients exhibiting reliable kinetic feature values, V̇o2 MRT was associated with ventilatory (e.g., FEV1 %predicted: P < 0.001; r = -0.35) and physical (e.g., V̇o2peak %predicted: P = 0.009; r = -0.18) impairments. Gains were mainly associated with cardiac function and ventilatory constraints, representing both response efficiency and limitation. Kinetic analyses are likely to be unreliable for patients with a WRpeak < 45 W. Whereas gains enrich analyses of physiological exercise responses, V̇o2 MRT shows potential to serve as a motivation-independent, physiological indicator of physical performance.NEW & NOTEWORTHY A constant work rate test that is standardly performed during a prerehabilitation assessment is unable to provide reliable kinetic feature values for chronic obstructive pulmonary disease (COPD) patients with a peak work rate below 45 W. For patients suffering from less severe impairments, kinetic analyses are a powerful tool to examine physiological exercise responses. Especially oxygen uptake mean response time can serve as a motivation-independent, physiological indicator of physical performance in patients with COPD.

Effect of High-Intensity Training and Asthma on the V˙O2 Kinetics of Adolescents

High-intensity interval training (HIIT) represents a potent stimulus to the dynamic oxygen uptake (V˙O2) response in adults, but whether the same is evident in youth is unknown. HIIT has also been suggested to place a lower demand on the respiratory system, decreasing the likelihood of exacerbation in those with respiratory conditions, such as asthma. Sixty-nine adolescents (13.6 ± 0.9 yr; 36 asthma) took part, 35 of which (17 asthma) participated in a 30-min HIIT intervention three times a week for 6 months. Each participant completed an incremental ramp test to volitional exhaustion and three heavy-intensity constant work rate tests to determine the dynamic V˙O2, heart rate, and deoxyhemoglobin response at baseline, midintervention, postintervention and at a 3-month follow-up. There was no influence of asthma at baseline or in response to the intervention. Participants in the intervention group demonstrated a faster V˙O2 time constant (τp) after intervention (intervention: 29.2 ± 5.7 s vs control: 34.2 ± 6.5 s; P = 0.003), with these differences maintained at follow-up (intervention: 32.5 ± 5.5 s vs control: 37.3 ± 8.7 s; P = 0.008). The intervention was associated with a speeding of the concentration of deoxyhemoglobin τ (pre: 20.1 ± 4.7 s vs post: 18.2 ± 4.1 s; P = 0.05) compared with a slowing over the same time period in the control participants (pre: 17.9 ± 4.9 s vs post: 20.1 ± 4.6 s; P = 0.012). Heart rate kinetics were not altered (pre: 46.5 ± 12.2 s vs post: 47.7 ± 11.1 s; P = 0.98). These findings highlight the potential utility of school-based HIIT as a strategy to enhance the V˙O2 kinetics of youth, regardless of the presence of asthma.

Fatigue Evaluation through Machine Learning and a Global Fatigue Descriptor.

Research in physiology and sports science has shown that fatigue, a complex psychophysiological phenomenon, has a relevant impact in performance and in the correct functioning of our motricity system, potentially being a cause of damage to the human organism. Fatigue can be seen as a subjective or objective phenomenon. Subjective fatigue corresponds to a mental and cognitive event, while fatigue referred as objective is a physical phenomenon. Despite the fact that subjective fatigue is often undervalued, only a physically and mentally healthy athlete is able to achieve top performance in a discipline. Therefore, we argue that physical training programs should address the preventive assessment of both subjective and objective fatigue mechanisms in order to minimize the risk of injuries. In this context, our paper presents a machine-learning system capable of extracting individual fatigue descriptors (IFDs) from electromyographic (EMG) and heart rate variability (HRV) measurements. Our novel approach, using two types of biosignals so that a global (mental and physical) fatigue assessment is taken into account, reflects the onset of fatigue by implementing a combination of a dimensionless (0-1) global fatigue descriptor (GFD) and a support vector machine (SVM) classifier. The system, based on 9 main combined features, achieves fatigue regime classification performances of 0.82 ± 0.24, ensuring a successful preventive assessment when dangerous fatigue levels are reached. Training data were acquired in a constant work rate test (executed by 14 subjects using a cycloergometry device), where the variable under study (fatigue) gradually increased until the volunteer reached an objective exhaustion state.

Uncovering the mechanisms of exertional dyspnoea in combined pulmonary fibrosis and emphysema.

The prevailing view is that exertional dyspnoea in patients with combined idiopathic pulmonary fibrosis (IPF) and emphysema (CPFE) can be largely explained by severe hypoxaemia. However, there is little evidence to support these assumptions.We prospectively contrasted the sensory and physiological responses to exercise in 42 CPFE and 16 IPF patients matched by the severity of exertional hypoxaemia. Emphysema and pulmonary fibrosis were quantified using computed tomography. Inspiratory constraints were assessed in a constant work rate test: capillary blood gases were obtained in a subset of patients.CPFE patients had lower exercise capacity despite less extensive fibrosis compared to IPF (p=0.004 and 0.02, respectively). Exertional dyspnoea was the key limiting symptom in 24 CPFE patients who showed significantly lower transfer factor, arterial carbon dioxide tension and ventilatory efficiency (higher minute ventilation (V'E)/carbon dioxide output (V'CO2 ) ratio) compared to those with less dyspnoea. However, there were no between-group differences in the likelihood of pulmonary hypertension by echocardiography (p=0.44). High dead space/tidal volume ratio, low capillary carbon dioxide tension emphysema severity (including admixed emphysema) and traction bronchiectasis were related to a high V'E/V'CO2 ratio in the more dyspnoeic group. V'E/V'CO2 nadir >50 (OR 9.43, 95% CI 5.28-13.6; p=0.0001) and total emphysema extent >15% (2.25, 1.28-3.54; p=0.01) predicted a high dyspnoea burden associated with severely reduced exercise capacity in CPFEContrary to current understanding, hypoxaemia per se is not the main determinant of exertional dyspnoea in CPFE. Poor ventilatory efficiency due to increased "wasted" ventilation in emphysematous areas and hyperventilation holds a key mechanistic role that deserves therapeutic attention.

Standardized measurement of breathlessness during exercise.

Exertional breathlessness is common and pervasive across various chronic disease populations. To accurately assess response to intervention and optimize clinical (symptom) management, detailed assessment of exertional breathlessness is imperative. This review provides an update on current approaches to assess exertional breathlessness and presents the need for individualized assessment of breathlessness standardized for the level of exertion. Breathlessness assessment tools commonly invite people to recall their breathlessness while at rest with reference to activities of daily living. To directly quantify breathlessness, however, requires assessment of the dimensions of breathlessness (e.g., sensory intensity, quality, and unpleasantness) in response to a standardized exercise stimulus. Different exercise stimuli (e.g., self-paced, incremental, and constant work rate exercise tests) have been used to elicit a breathlessness response. Self-paced (e.g., 6-min walk test) and incremental exercise tests assess exercise tolerance or endurance, and are not recommended for assessment of exertional breathlessness. Constant work rate tests, however, including recently validated 3-min constant-rate stair stepping and walking tests, standardize the exercise stimulus to enable the breathlessness response to be directly quantified and monitored over time. To adequately guide symptom management and assess intervention efficacy, clinicians and researchers should assess breathlessness with multidimensional assessment tools in response to a standardized and individualized exercise stimulus.

Role Of Gender In Anti-oxidant Response To A Bout Of Aerobic Exercise In Healthy Adults

Aerobic exercise acutely increases the production of reactive oxygen species (ROS), which creates an imbalance between free radicals and the body’s antioxidant defenses, resulting in increased oxidative stress. Oxidative stress levels are reportedly higher in males compared to females, however there is limited knowledge regarding the role of gender in the antioxidant response following an acute bout of aerobic exercise. PURPOSE: To determine whether changes in serum antioxidant levels after an acute aerobic exercise bout differed between genders. METHODS: The study comprised of 15 healthy adults (9 females, 6 males; age 27±8 years; BMI 24±3 kg/m2) enrolled in the NIH Fatigue in Healthy Individuals Protocol (NCT00888563). During the first visit, subjects completed a treadmill cardiopulmonary exercise test (CPET) to volitional exhaustion. On a separate visit, subjects performed a vigorous-intensity continuous work rate (WR) test, to volitional exhaustion on the treadmill. Serum samples were collected before and immediately after the vigorous exercise bout. A Human Oxidative Stress Multiplex panel was used to determine serum peroxidase (PRX2) and catalase levels. Student’s t-tests were performed between genders for WR and antioxidant levels. RESULTS: Males performed vigorous-intensity exercise at a higher WR than females (p<0.0001). No difference was found in baseline PRX2 and catalase levels between males and females. Relative change in PRX2 (+32% in males; -17% in females) and catalase (+18% in males; -11% in females) was different between genders after a vigorous bout of aerobic exercise (p=0.0136, p=0.0344, respectively). This difference became insignificant when WR was accounted for. CONCLUSION: This study suggests that higher levels of oxidative stress in males may be explained by higher work rates. However, response to exercise-induced oxidative stress demonstrated that males (6 of 6) increased anti-oxidant levels, while females (8 out of 9) showed decreased levels. Previous studies have suggested that gender differences in oxidative stress may be related to an increased production of ROS by NADPH-oxidase in males, or antioxidant properties of estrogen which may assist in minimizing oxidative stress in females. Funding: National Institute of Nursing Research, Division of Intramural Research

Box-Jenkins Transfer Function Modelling for Reliable Determination of VO2 Kinetics in Patients with COPD

Oxygen uptake (VO2) kinetics provide information about the ability to respond to the increased physical load during a constant work rate test (CWRT). Box-Jenkins transfer function (BJ-TF) models can extract kinetic features from the phase II VO2 response during a CWRT, without being affected by unwanted noise contributions (e.g., phase I contribution or measurement noise). CWRT data of 18 COPD patients were used to compare model fits and kinetic feature values between BJ-TF models and three typically applied exponential modelling methods. Autocorrelation tests and normalised root-mean-squared error values (BJ-TF: 2.8 ± 1.3%; exponential methods A, B and C: 10.5 ± 5.8%, 11.3 ± 5.2% and 12.1 ± 7.0%; p &lt; 0.05) showed that BJ-TF models, in contrast to exponential models, could account for the most important noise contributions. This led to more reliable kinetic feature values compared to methods A and B (e.g., mean response time (MRT), BJ-TF: 74 ± 20 s; methods A-B: 100 ± 56 s–88 ± 52 s; p &lt; 0.05). Only exponential modelling method C provided kinetic feature values comparable to BJ-TF features values (e.g., MRT: 75 ± 20 s). Based on theoretical considerations, we recommend using BJ-TF models, rather than exponential models, for reliable determinations of VO2 kinetics.

The Reconstitution of W' Depends on Both Work and Recovery Characteristics.

This study aimed to investigate the effects of different work and recovery characteristics on the W' reconstitution and to test the predictive capabilities of the W'BAL model. Eleven male participants (22 ± 3 yr, 55 ± 4 mL·kg⋅min) completed three to five constant work rate tests to determine CP and W'. Subsequently, subjects performed 12 experimental trials, each comprising two exhaustive constant work rate bouts (i.e., WB1 and WB2), interspersed by an active recovery interval. In each trial, work bout characteristics (P4 or P8, i.e., the work rate predicted to result in exhaustion in 4 and 8 min, respectively), recovery work rate (33% CP or 66% CP), and recovery duration (2, 4, or 6 min) were varied. Actual (W'ACT) and model-predicted (W'PRED) reconstitution values of W' were calculated. After 2, 4, and 6 min recovery, W'ACT averaged 46% ± 2.7%, 51.2% ± 3.3%, and 59.4% ± 4.1%, respectively (P = 0.003). W'ACT was 9.4% higher after recovery at 33% CP than at 66% CP (56.9% ± 3.9% vs 47.5% ± 3.2%) (P = 0.019). P4 exercise yielded a 11.3% higher W'ACT than P8 exercise (57.8% ± 3.9% vs 46.5% ± 2.7%) (P = 0.001). W'ACT was higher than W'PRED in the conditions P4-2 min (+29.7%), P4-4 min (+18.4%), and P8-2 min (+18%) (P < 0.01). A strong correlation (R = 0.68) between the rate of W' depletion and W' recovery was found (P = 0.001). This study demonstrated that both the work and recovery characteristics of a prior exhaustive exercise bout can affect the W' reconstitution. Results revealed a slower W' reconstitution when the rate of W' depletion was slower as well. Furthermore, it was shown that the current W'BAL model underestimates actual W' reconstitution, especially after shorter recovery.

Methodological Approaches and Related Challenges Associated With the Determination of Critical Power and Curvature Constant.

Muniz-Pumares, D, Karsten, B, Triska, C, and Glaister, M. Methodological approaches and related challenges associated with the determination of critical power and W'. J Strength Cond Res 33(2): 584-596, 2019-The relationship between exercise intensity and time to task failure (P-T relationship) is hyperbolic, and characterized by its asymptote (critical power [CP]) and curvature constant (W'). The determination of these parameters is of interest for researchers and practitioners, but the testing protocol for CP and W' determination has not yet been standardized. Conventionally, a series of constant work rate (CWR) tests to task failure have been used to construct the P-T relationship. However, the duration, number, and recovery between predictive CWR and the mathematical model (hyperbolic or derived linear models) are known to affect CP and W'. Moreover, repeating CWR may be deemed as a cumbersome and impractical protocol. Recently, CP and W' have been determined in field and laboratory settings using time trials, but the validity of these methods has raised concerns. Alternatively, a 3-minute all-out test (3MT) has been suggested, as it provides a simpler method for the determination of CP and W', whereby power output at the end of the test represents CP, and the amount of work performed above this end-test power equates to W'. However, the 3MT still requires an initial incremental test and may overestimate CP. The aim of this review is, therefore, to appraise current methods to estimate CP and W', providing guidelines and suggestions for future research where appropriate.

A randomized cross-over trial on the direct effects of oxygen supplementation therapy using different devices on cycle endurance in hypoxemic patients with Interstitial Lung Disease

BackgroundIn patients with interstitial lung disease (ILD) a cardinal feature is exercise intolerance, often associated with significant dyspnea and severe hypoxemia. Supplemental oxygen therapy may be offered during exercise. The Oxymizer is a nasal cannula with an incorporated reservoir with the potential to deliver higher oxygen doses to the patient.ObjectiveThe primary aim was to investigate the effect of supplemental oxygen delivered via Oxymizer compared to a conventional nasal cannula (CNC) in patients with ILD during constant work rate tests (CWRT). Secondary aim was to evaluate effects on oxygen saturation (SpO2), dyspnea and heart rate at isotime.MethodsIn this randomized crossover study 24 ILD patients established on long-term oxygen treatment were included. Patients performed four cycling CWRT at 70% of their peak work rate; twice with the Oxymizer and twice with the CNC.ResultsTwenty-one patients finished all CWRTs (age 60 ± 10.9 years, VC 55.4 ± 23.0%predicted). Cycle endurance time was significantly higher while using the Oxymizer compared to CNC (718 ± 485 vs. 680 ± 579 seconds, p = 0.02), and SpO2 at isotime was significantly higher while using the Oxymizer (85.5 ± 6.7 vs. 82.8± 7.2, p = 0.01). Fifteen of the 21 (71%) patients cycled longer with the Oxymizer. There were no significant differences for dyspnea and heart rate.ConclusionsSupplemental oxygen provided by the Oxymizer significantly, but modestly, improved cycle endurance time and SpO2 at isotime in ILD patients compared to CNC.