Effects of surgical masks on the responses to constant work‐rate cycling performed at different intensity domains

AbstractThe purpose of this study was to investigate whether a tethered-swimming incremental test comprising small increases in resistive force applied every 60 seconds could delineate the isocapnic region during rapidly-incremented exercise. Sixteen competitive swimmers (male, n = 11; female, n = 5) performed: (a) a test to determine highest force during 30 seconds of all-out tethered swimming (Favg) and the ΔF, which represented the difference between Favg and the force required to maintain body alignment (Fbase), and (b) an incremental test beginning with 60 seconds of tethered swimming against a load that exceeded Fbase by 30% of ΔF followed by increments of 5% of ΔF every 60 seconds. This incremental test was continued until the limit of tolerance with pulmonary gas exchange (rates of oxygen uptake and carbon dioxide production) and ventilatory (rate of minute ventilation) data collected breath by breath. These data were subsequently analyzed to determine whether two breakpoints defining the isocapnic region (i.e., gas exchange threshold and respiratory compensation point) were present. We also determined the peak rate of O2 uptake and exercise economy during the incremental test. The gas exchange threshold and respiratory compensation point were observed for each test such that the associated metabolic rates, which bound the heavy-intensity domain during constant-work-rate exercise, could be determined. Significant correlations (Spearman’s) were observed for exercise economy along with (a) peak rate of oxygen uptake (ρ = .562; p < 0.025), and (b) metabolic rate at gas exchange threshold (ρ = −.759; p < 0.005). A rapidly-incremented tethered-swimming test allows for determination of the metabolic rates that define zones for domain-specific constant-work-rate training.

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O2 Uptake in hyperthyroidism during constant work rate and incremental exercise

European Journal of Applied Physiology and Occupational Physiology ◽

10.1007/bf00571550 ◽

1991 ◽

Vol 62 (4) ◽

pp. 261-267 ◽

Cited By ~ 8

Author(s):

I. Ben-Dov ◽

K. E. Sietsema ◽

K. Wasserman

Keyword(s):

Work Rate ◽

Incremental Exercise ◽

O2 Uptake ◽

Constant Work Rate

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Muscle fatigue and exhaustion during dynamic leg exercise in normoxia and hypobaric hypoxia

Journal of Applied Physiology ◽

10.1152/jappl.1996.81.5.1891 ◽

1996 ◽

Vol 81 (5) ◽

pp. 1891-1900 ◽

Cited By ~ 51

Author(s):

Charles S. Fulco ◽

Steven F. Lewis ◽

Peter N. Frykman ◽

Robert Boushel ◽

Sinclair Smith ◽

...

Keyword(s):

Muscle Fatigue ◽

Hypobaric Hypoxia ◽

Knee Extension ◽

Work Rate ◽

Dynamic Exercise ◽

Time To Exhaustion ◽

Electromyographic Activity ◽

Constant Work Rate ◽

Generating Capacity ◽

Leg Exercise

Fulco, Charles S., Steven F. Lewis, Peter N. Frykman, Robert Boushel, Sinclair Smith, Everett A. Harman, Allen Cymerman, and Kent B. Pandolf. Muscle fatigue and exhaustion during dynamic leg exercise in normoxia and hypobaric hypoxia. J. Appl. Physiol. 81(5): 1891–1900, 1996.—Using an exercise device that integrates maximal voluntary static contraction (MVC) of knee extensor muscles with dynamic knee extension, we compared progressive muscle fatigue, i.e., rate of decline in force-generating capacity, in normoxia (758 Torr) and hypobaric hypoxia (464 Torr). Eight healthy men performed exhaustive constant work rate knee extension (21 ± 3 W, 79 ± 2 and 87 ± 2% of 1-leg knee extension O2 peak uptake for normoxia and hypobaria, respectively) from knee angles of 90–150° at a rate of 1 Hz. MVC (90° knee angle) was performed before dynamic exercise and during ≤5-s pauses every 2 min of dynamic exercise. MVC force was 578 ± 29 N in normoxia and 569 ± 29 N in hypobaria before exercise and fell, at exhaustion, to similar levels (265 ± 10 and 284 ± 20 N for normoxia and hypobaria, respectively; P > 0.05) that were higher ( P < 0.01) than peak force of constant work rate knee extension (98 ± 10 N, 18 ± 3% of MVC). Time to exhaustion was 56% shorter for hypobaria than for normoxia (19 ± 5 vs. 43 ± 7 min, respectively; P < 0.01), and rate of right leg MVC fall was nearly twofold greater for hypobaria than for normoxia (mean slope = −22.3 vs. −11.9 N/min, respectively; P < 0.05). With increasing duration of dynamic exercise for normoxia and hypobaria, integrated electromyographic activity during MVC fell progressively with MVC force, implying attenuated maximal muscle excitation. Exhaustion, per se, was postulated to relate more closely to impaired shortening velocity than to failure of force-generating capacity.

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Muscle metabolic responses to exercise above and below the “critical power” assessed using 31P-MRS

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00731.2007 ◽

2008 ◽

Vol 294 (2) ◽

pp. R585-R593 ◽

Cited By ~ 246

Author(s):

Andrew M. Jones ◽

Daryl P. Wilkerson ◽

Fred DiMenna ◽

Jonathan Fulford ◽

David C. Poole

Keyword(s):

Critical Power ◽

Quadriceps Muscle ◽

High Energy ◽

Knee Extension ◽

Work Rate ◽

Metabolic Responses ◽

Time To Exhaustion ◽

Resonance Spectroscopy ◽

High Energy Phosphates ◽

Constant Work Rate

We tested the hypothesis that the asymptote of the hyperbolic relationship between work rate and time to exhaustion during muscular exercise, the “critical power” (CP), represents the highest constant work rate that can be sustained without a progressive loss of homeostasis [as assessed using 31P magnetic resonance spectroscopy (MRS) measurements of muscle metabolites]. Six healthy male subjects initially completed single-leg knee-extension exercise at three to four different constant work rates to the limit of tolerance (range 3–18 min) for estimation of the CP (mean ± SD, 20 ± 2 W). Subsequently, the subjects exercised at work rates 10% below CP (<CP) for 20 min and 10% above CP (>CP) for as long as possible, while the metabolic responses in the contracting quadriceps muscle, i.e., phosphorylcreatine concentration ([PCr]), Pi concentration ([Pi]), and pH, were estimated using 31P-MRS. All subjects completed 20 min of <CP exercise without duress, whereas the limit of tolerance during >CP exercise was 14.7 ± 7.1 min. During <CP exercise, stable values for [PCr], [Pi], and pH were attained within 3 min after the onset of exercise, and there were no further significant changes in these variables (end-exercise values = 68 ± 11% of baseline [PCr], 314 ± 216% of baseline [Pi], and pH 7.01 ± 0.03). During >CP exercise, however, [PCr] continued to fall to the point of exhaustion and [Pi] and pH changed precipitously to values that are typically observed at the termination of high-intensity exhaustive exercise (end-exercise values = 26 ± 16% of baseline [PCr], 564 ± 167% of baseline [Pi], and pH 6.87 ± 0.10, all P < 0.05 vs. <CP exercise). These data support the hypothesis that the CP represents the highest constant work rate that can be sustained without a progressive depletion of muscle high-energy phosphates and a rapid accumulation of metabolites (i.e., H+ concentration and [Pi]), which have been associated with the fatigue process.

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Establishing the V̇o2 versus constant-work-rate relationship from ramp-incremental exercise: simple strategies for an unsolved problem

Journal of Applied Physiology ◽

10.1152/japplphysiol.00508.2019 ◽

2019 ◽

Vol 127 (6) ◽

pp. 1519-1527 ◽

Cited By ~ 13

Author(s):

Danilo Iannetta ◽

Rafael de Almeida Azevedo ◽

Daniel A. Keir ◽

Juan M. Murias

Keyword(s):

Lactate Threshold ◽

Unsolved Problem ◽

Critical Power ◽

Work Rate ◽

Incremental Exercise ◽

Mean Response Time ◽

Constant Work Rate ◽

Ramp Exercise ◽

The Mean ◽

Highly Correlated

The dissociation between constant work rate of O2 uptake (V̇o2) and ramp V̇o2 at a given work rate might be mitigated during slowly increasing ramp protocols. This study characterized the V̇o2 dynamics in response to five different ramp protocols and constant-work-rate trials at the maximal metabolic steady state (MMSS) to characterize 1) the V̇o2 gain (G) in the moderate, heavy, and severe domains, 2) the mean response time of V̇o2 (MRT), and 3) the work rates at lactate threshold (LT) and respiratory compensation point (RCP). Eleven young individuals performed five ramp tests (5, 10, 15, 25, and 30 W/min), four to five time-to-exhaustions for critical power estimation, and two to three constant-work-rate trials for confirmation of the work rate at MMSS. G was greatest during the slowest ramp and progressively decreased with increasing ramp slopes (from ~12 to ~8 ml·min−1·W−1, P < 0.05). The MRT was smallest during the slowest ramp slopes and progressively increased with faster ramp slopes (1 ± 1, 2 ± 1, 5 ± 3, and 10 ± 4, 15 ± 6 W, P < 0.05). After “left shifting” the ramp V̇o2 by the MRT, the work rate at LT was constant regardless of the ramp slope (~150 W, P > 0.05). The work rate at MMSS was 215 ± 55 W and was similar and highly correlated with the work rate at RCP during the 5 W/min ramp ( P > 0.05, r = 0.99; Lin’s concordance coefficient = 0.99; bias = −3 W; root mean square error = 6 W). Findings showed that the dynamics of V̇o2 (i.e., G) during ramp exercise explain the apparent dichotomy existing with constant-work-rate exercise. When these dynamics are appropriately “resolved”, LT is constant regardless of the ramp slope of choice, and RCP and MMSS display minimal variations between each other. NEW & NOTEWORTHY This study demonstrates that the dynamics of V̇o2 during ramp-incremental exercise are dependent on the characteristics of the increments in work rate, such that during slow-incrementing ramp protocols the magnitude of the dissociation between ramp V̇o2 and constant V̇o2 at a given work rate is reduced. Accurately accounting for these dynamics ensures correct characterizations of the V̇o2 kinetics at ramp onset and allows appropriate comparisons between ramp and constant-work-rate exercise-derived indexes of exercise intensity.

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Sensory-mechanical relationships during high-intensity, constant-work-rate exercise in COPD

Journal of Applied Physiology ◽

10.1152/japplphysiol.01470.2005 ◽

2006 ◽

Vol 101 (4) ◽

pp. 1025-1035 ◽

Cited By ~ 141

Author(s):

Denis E. O’Donnell ◽

Alan L. Hamilton ◽

Katherine A. Webb

Keyword(s):

Chronic Obstructive Pulmonary Disease ◽

Pulmonary Disease ◽

Esophageal Pressure ◽

Work Rate ◽

Chronic Obstructive ◽

Dynamic Hyperinflation ◽

Obstructive Pulmonary Disease ◽

Displacement Ratio ◽

Constant Work Rate ◽

Anticholinergic Bronchodilator

During constant-work-rate exercise in chronic obstructive pulmonary disease, dyspnea increases steeply once inspiratory reserve volume (IRV) falls to a critical level that prevents further expansion of tidal volume (Vt). We studied the effects of this mechanical restriction on the quality and intensity of exertional dyspnea and examined the impact of an anticholinergic bronchodilator. In a randomized, double-blind, crossover study, 18 patients with chronic obstructive pulmonary disease (forced expiratory volume in 1 s = 40 ± 3%predicted; mean ± SE) inhaled tiotropium 18 μg or placebo once daily for 7–10 days each. Pulmonary function tests and symptom-limited cycle exercise at 75% of each patient’s maximal work capacity were performed 2 h after dosing. Dyspnea intensity (Borg scale), operating lung volumes, breathing pattern, and esophageal pressure ( n = 11) were measured during exercise. Dynamic hyperinflation reached its maximal value early in exercise and was associated with only mild increases in dyspnea intensity and the effort-displacement ratio, which is defined as the ratio between tidal swings of esophageal pressure (expressed relative to maximum inspiratory pressure) and Vt (expressed relative to predicted vital capacity). After a minimal IRV of 0.5 ± 0.1 liter was reached, both dyspnea and the effort-displacement ratio rose steeply until an intolerable level was reached. Tiotropium did not alter dyspnea-IRV relationships, but the increase in resting and exercise inspiratory capacity was associated with an improved effort-displacement ratio throughout exercise. Once a critically low IRV was reached during exercise, dyspnea rose with the disparity between respiratory effort and the Vt response. Changes in dyspnea intensity after tiotropium were positively correlated with changes in this index of neuromechanical coupling.

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Effects of separate rib cage and abdominal restriction on exercise performance in normal humans

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.6.2020 ◽

1985 ◽

Vol 58 (6) ◽

pp. 2020-2026 ◽

Cited By ~ 25

Author(s):

S. N. Hussain ◽

B. Rabinovitch ◽

P. T. Macklem ◽

R. L. Pardy

Keyword(s):

Minute Ventilation ◽

Normal Subjects ◽

Cycle Ergometer ◽

Abdominal Muscle ◽

Work Rate ◽

Abdominal Pressure ◽

Transdiaphragmatic Pressure ◽

Rib Cage ◽

Constant Work Rate ◽

And Control

We assessed the effects of selective restriction of movements of the rib cage (Res,rc) and abdomen (Res,ab) on ventilatory pattern, transdiaphragmatic pressure (Pdi), and electrical activity of the diaphragm (Edi) in five normal subjects exercising at a constant work rate (80% of maximum power output) on a cycle ergometer till exhaustion. Restriction of movements was achieved by an inelastic corset applied tightly around the rib cage or abdomen. Edi was recorded by an esophageal electrode, rectified, and then integrated, and peak values during inspiration were measured. Each subject exercised at the same work rate on 3 days: with Res,rc, with Res,ab, and without restriction (control). Res,rc but not Res,ab reduced exercise time (tlim). Up to tlim, minute ventilation (VE) was similar in all three conditions. At any level of VE, however, Res,rc decreased tidal volume and inspiratory and expiratory time, whereas Res,ab had no effect on the pattern of breathing. Res,ab was associated with higher inspiratory Pdi swings at any level of VE, whereas peak Edi was similar to control. Inspiratory Pdi swings were the same with Res,rc as control, but the peak Edi for a given Pdi was greater with Res,rc (P less than 0.05). During Res,rc the abdominal pressure swings in expiration were greater than with Res,ab and control. We conclude that Res,rc altered the pattern of breathing in normal subjects in high-intensity exercise, decreased diaphragmatic contractility, increased abdominal muscle recruitment in expiration, and reduced tlim. On the other hand, Res,ab had no effect on breathing pattern or tlim but was associated with increased diaphragmatic contractility.

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The relationship between oxygen uptake reserve and heart rate reserve is affected by intensity and duration during aerobic exercise at constant work rate

Applied Physiology Nutrition and Metabolism ◽

10.1139/h11-100 ◽

2011 ◽

Vol 36 (6) ◽

pp. 839-847 ◽

Cited By ~ 8

Author(s):

Felipe A. Cunha ◽

Adrian W. Midgley ◽

Walace D. Monteiro ◽

Felipe K. Campos ◽

Paulo T.V. Farinatti

Keyword(s):

Heart Rate ◽

Oxygen Uptake ◽

Exercise Testing ◽

Exercise Intensity ◽

Maximal Exercise ◽

Work Rate ◽

Heart Rate Reserve ◽

Constant Work Rate ◽

The Stability ◽

The Relationship

The relationship between the percentage of heart rate reserve (%HRR) and percentage of oxygen uptake reserve (%VO2R) has been recommended for prescribing aerobic exercise intensity. However, this relationship was derived from progressive maximal exercise testing data, and the stability of the relationship during prolonged exercise at a constant work rate has not been established. The main aim of this study was to investigate the stability of the %VO2R–%HRR relationship during prolonged treadmill exercise bouts performed at 3 different constant work rates. Twenty-eight men performed 4 exercise tests: (i) a ramp-incremental maximal exercise test to determine maximal heart rate (HRmax) and maximal oxygen uptake (VO2max) and (ii) three 40-min exercise bouts at 60%, 70%, and 80% VO2R. HR and VO2 significantly increased over time and were influenced by exercise intensity (p < 0.001 and p = 0.004, respectively). A 1:1 relationship between %HRR and %VO2R, and between %HRR and %VO2max, was not observed, with mean differences of 8% (t = 5.2, p < 0.001) and 6% (t = 4.8, p < 0.001), respectively. The VO2 values predicted from the ACSM running equation were all significantly higher than the observed VO2 values (p < 0.001 for all comparisons), whereas a difference for HR was observed only for the tenth min of exercise at 80% VO2R (p = 0.041). In conclusion, the main finding of this study was that the %HRR–%VO2R relationship determined by linear regression, obtained from progressive maximal exercise testing, did not apply to prolonged treadmill running performed at 3 work rates.

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Predictors of low endurance time in constant work rate cycle testing in COPD

10.1183/13993003.congress-2019.oa3812 ◽

2019 ◽

Cited By ~ 1

Author(s):

Richard Casaburi ◽

Alan Hamilton ◽

Martijn Spruit ◽

Debora Merrill ◽

Gale Harding ◽

...

Keyword(s):

Work Rate ◽

Endurance Time ◽

Constant Work Rate

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