An Exercise Model to Study Progressive Muscle Fatigue During Constant Work Rate Exercise on a Cycle Ergometer

2003 ◽  
Author(s):  
Charles S. Fulco ◽  
Paolo Bonato ◽  
Don Gilmore ◽  
Steven F. Lewis
Keyword(s):  
Muscle Fatigue ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Constant Work Rate

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

1996 ◽  
Vol 81 (5) ◽  
pp. 1891-1900 ◽  
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.

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

1985 ◽  
Vol 58 (6) ◽  
pp. 2020-2026 ◽  
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.

Lactic acidosis as a facilitator of oxyhemoglobin dissociation during exercise

1994 ◽  
Vol 76 (4) ◽  
pp. 1462-1467 ◽  
Author(s):  
W. Stringer ◽  
K. Wasserman ◽  
R. Casaburi ◽  
J. Porszasz ◽  
K. Maehara ◽  
...  
Keyword(s):  
Lactic Acidosis ◽  
Femoral Vein ◽  
Lactate Concentration ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Exercise Tests ◽  
Ergometer Exercise ◽  
Constant Work Rate ◽  
Slow Rise ◽  
Lactic Acidosis Threshold

The slow rise in O2 uptake (VO2), which has been shown to be linearly correlated with the increase in lactate concentration during heavy constant work rate exercise, led us to investigate the role of H+ from lactic acid in facilitating oxyhemoglobin (O2Hb) dissociation. We measured femoral venous PO2, O2Hb saturation, pH, PCO2, lactate, and standard HCO3- during increasing work rate and two constant work rate cycle ergometer exercise tests [below and above the lactic acidosis threshold (LAT)] in two groups of five healthy subjects. Mean end-exercise femoral vein blood and VO2 values for the below- and above-LAT square waves and the increasing work rate protocol were, respectively, PO2 of 19.8 +/- 2.1 (SD), 18.8 +/- 4.7, and 19.8 +/- 3.3 Torr; O2 saturation of 22.5 +/- 4.1, 13.8 +/- 4.2, and 18.5 +/- 6.3%; pH of 7.26 +/- 0.01, 7.02 +/- 0.11, and 7.09 +/- 0.07; lactate of 1.9 +/- 0.9, 11.0 +/- 3.8, and 8.3 +/- 2.9 mmol/l; and VO2 of 1.77 +/- 0.24, 3.36 +/- 0.4, and 3.91 +/- 0.68 l/min. End-exercise femoral vein PO2 did not differ statistically for the three protocols, whereas O2Hb saturation continued to decrease for work rates above LAT. We conclude that decreasing capillary PO2 accounted for most of the O2Hb dissociation during below-LAT exercise and that acidification of muscle capillary blood due to lactic acidosis accounted for virtually all of the O2Hb dissociation above LAT.

PROGRESSIVE QUADRICEPS FEMORIS MUSCLE FATIGUE DURING CONSTANT WORK RATE DYNAMIC EXERCISE

1995 ◽  
Vol 27 (Supplement) ◽  
pp. S79
Author(s):  
S. F. Lewis ◽  
C. S. Fulco ◽  
P. Frykman ◽  
R. Boushel ◽  
S. Smith ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Quadriceps Femoris ◽  
Work Rate ◽  
Dynamic Exercise ◽  
Quadriceps Femoris Muscle ◽  
Constant Work Rate ◽  
Rate Dynamic ◽  
Femoris Muscle

Ventilatory response to helium-oxygen breathing during exercise: effect of airway anesthesia

1997 ◽  
Vol 83 (1) ◽  
pp. 82-88 ◽  
Author(s):  
Bharath S. Krishnan ◽  
Ron E. Clemens ◽  
Trevor A. Zintel ◽  
Martin J. Stockwell ◽  
Charles G. Gallagher
Keyword(s):  
Ventilatory Response ◽  
Breathing Circuit ◽  
Minute Ventilation ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Upper Airways ◽  
Warm Up ◽  
Oxygen Breathing ◽  
Exercise Effect ◽  
Constant Work Rate

Krishnan, Bharath S., Ron E. Clemens, Trevor A. Zintel, Martin J. Stockwell, and Charles G. Gallagher. Ventilatory response to helium-oxygen breathing during exercise: effect of airway anesthesia. J. Appl. Physiol. 83(1): 82–88, 1997.—The substitution of a normoxic helium mixture (HeO2) for room air (Air) during exercise results in a sustained hyperventilation, which is present even in the first breath. We hypothesized that this response is dependent on intact airway afferents; if so, airway anesthesia (Anesthesia) should affect this response. Anesthesia was administered to the upper airways by topical application and to lower central airways by aerosol inhalation and was confirmed to be effective for over 15 min. Subjects performed constant work-rate exercise (CWE) at 69 ± 2 (SE) % maximal work rate on a cycle ergometer on three separate days: twice after saline inhalation ( days 1 and 3) and once after Anesthesia ( day 2). CWE commenced after a brief warm-up, with subjects breathing Air for the first 5 min (Air-1), HeO2 for the next 3 min, and Air again until the end of CWE (Air-2). The resistance of the breathing circuit was matched for Air and HeO2. Breathing HeO2 resulted in a small but significant increase in minute ventilation (V˙i) and decrease in alveolar [Formula: see text] in both the Saline (average of 2 saline tests; not significant) and Anesthesia tests. Although Anesthesia had no effect on the sustained hyperventilatory response to HeO2breathing, theV˙i transients within the first six breaths of HeO2 were significantly attenuated with Anesthesia. We conclude that theV˙i response to HeO2 is not simply due to a reduction in external tubing resistance and that, in humans, airway afferents mediate the transient but not the sustained hyperventilatory response to HeO2 breathing during exercise.

Quantitation of progressive muscle fatigue during dynamic leg exercise in humans

1995 ◽  
Vol 79 (6) ◽  
pp. 2154-2162 ◽  
Author(s):  
C. S. Fulco ◽  
S. F. Lewis ◽  
P. N. Frykman ◽  
R. Boushel ◽  
S. Smith ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Quadriceps Femoris ◽  
Work Rate ◽  
Myoelectric Activity ◽  
Work Intensity ◽  
O2 Uptake ◽  
Constant Work Rate ◽  
Leg Exercise

There is virtually no published information on muscle fatigue, defined as a gradual decline in force-generating capacity, during conventional dynamic (D) leg exercise. To quantitate progression of fatigue, we developed 1) a model featuring integration of maximal voluntary static contraction (MVC) of knee extension (KE) muscles with ongoing DKE and 2) a device that allows frequent rapid transfer between DKE isolated to the quadriceps femoris muscles and measurement of KE MVC. Eight healthy men performed graded and submaximal constant work rate one-leg DKE to exhaustion while seated. Work rate, a product of a contraction rate (1 Hz), force measured at the ankle, and distance of ankle movement from 90 degrees to 150 degrees of KE, was precisely controlled. Lack of rise in myoelectric activity in biceps femoris of the active leg during DKE and MVC was consistent with restriction of muscle action to quadriceps femoris. The slope of the linear relationship between O2 uptake and work rate was 13.7 ml O2/W (r = 0.93). This slope and the increase of heart rate relative to increasing work intensity agreed with published values for D leg exercise. Test-retest values for O2 uptake were similar (P > 0.05) for matched DKE work rates. To track fatigue, MVC (90 degrees knee angle) was performed every 2 min of DKE. After 4 min of DKE at work rates corresponding to (mean +/- SE) 66 +/- 2, 78 +/- 2, and 100% of peak DKE O2 uptake, MVC fell to 95 +/- 3, 90 +/- 5, and 65 +/- 7%* of MVC of rested muscle, respectively (*P < 0.01 from previous work rates). Virtually identical declines in MVC were observed by the end of graded work rate DKE and submaximal constant work rate DKE tests. Quantitation of progressive muscle fatigue during D leg exercise provides a framework to study the effects of a variety of interventions on the fatigue process and may permit unique insights into the involved mechanisms.

Effect of beta-adrenergic blockade on respiratory and metabolic responses to exercise

1981 ◽  
Vol 51 (4) ◽  
pp. 788-793 ◽  
Author(s):  
O. P. Twentyman ◽  
A. Disley ◽  
H. R. Gribbin ◽  
K. G. Alberti ◽  
A. E. Tattersfield
Keyword(s):  
Venous Blood ◽  
Normal Subjects ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Adrenergic Blockade ◽  
Early Exercise ◽  
Co2 Output ◽  
Initial Reduction ◽  
Progressive Exercise ◽  
Constant Work Rate

The responses to oral propranolol (80 mg) and placebo were compared in normal subjects during three studies on a cycle ergometer (progressive exercise and two 5-min constant work rate studies at 50 and 70% maximum). Heart rate (HR), ventilation (VE), CO2 output (VCO2) and O2 uptake (VO2) were measured in each study and metabolites in venous blood in the 70% study. Propranolol reduced HR in all studies and endurance time during progressive exercise. During constant-work-rate exercise the changes with propranolol depended on time and work rate. At 50% max, VO2, VCO2, and VE were reduced in early exercise but were similar by min 5. At 70% max, VO2 and VCO2 were again lower initially with propranolol but then rose more rapidly. By min 5 VE was greater with propranolol, coinciding with a rapidly rising venous lactate. We interpret the initial reduction in VO2 and VCO2 to reduced cardiac output and muscle perfusion with propranolol. The resulting increase in anaerobic metabolism during heavy exercise would explain the increased VE at min 5. The metabolic data are compatible with glycogen being the predominant muscle fuel.

scholarly journals Oxygen uptake dynamics during high-intensity exercise in children and adults

1991 ◽  
Vol 70 (2) ◽  
pp. 841-848 ◽  
Author(s):  
Y. Armon ◽  
D. M. Cooper ◽  
R. Flores ◽  
S. Zanconato ◽  
T. J. Barstow
Keyword(s):  
High Intensity ◽  
Cycle Ergometer ◽  
Work Rate ◽  
High Intensity Exercise ◽  
O2 Uptake ◽  
Low Intensity ◽  
Ergometer Exercise ◽  
Constant Work Rate ◽  
The Difference ◽  
Low Intensity Exercise

We hypothesized that the O2 uptake (Vo2) response to high-intensity exercise would be different in children than in adults. To test this hypothesis, 22 children (6-12 yr old) and 7 adults (27-40 yr old) performed 6 min of constant-work-rate cycle-ergometer exercise. Sixteen children performed a single test above their anaerobic threshold (AT). In a separate protocol, six children and all adults exercised at low and high intensity. Low-intensity exercise corresponded to the work rate at 80% of each subject's AT. High-intensity exercise (above the AT) was determined first by calculating the difference in work rate between the AT and the maximal Vo2 (delta). Twenty-five, 50, and 75% of this difference were added to the work rate at the subject's AT, and these work rates were referred to as 25% delta, 50% delta, and 75% delta. For exercise at 50% delta and 75% delta, Vo2 increased throughout exercise (O2 drift, linear regression slope of Vo2 as a function of time from 3 to 6 min) in all the adults, and the magnitude of the drift was correlated with increasing work rates in the above-AT range (r = 0.91, P less than 0.0001). In contrast, no O2 drift was observed in over half of the children during above-AT exercise. The O2 drifts were much higher in adults (1.76 +/- 0.63 ml O2.kg-1.min-2 at 75% delta) than in children (0.20 +/- 0.42, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative Measurement Properties of Constant Work-Rate Cycling and Endurance Shuttle Walking in Patients with COPD: Data from the TORRACTO Study

Pneumologie ◽  
2018 ◽  
Vol 72 (S 01) ◽  
pp. S90-S90
Author(s):  
K Siemon ◽  
F Maltais ◽  
DE O'Donnell ◽  
A Hamilton ◽  
Y Zhao ◽  
...  
Keyword(s):  
Work Rate ◽  
Measurement Properties ◽  
Comparative Measurement ◽  
Constant Work Rate

scholarly journals Confinement, partial sleep deprivation and defined physical activity–influence on cardiorespiratory regulation and capacity

2021 ◽  
Author(s):  
Jessica Koschate ◽  
Uwe Drescher ◽  
Uwe Hoffmann
Keyword(s):  
Physical Activity ◽  
Cardiorespiratory Fitness ◽  
Space Mission ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Binary Sequences ◽  
Kinetics Parameters ◽  
Slow Heart Rate ◽  
Partial Sleep Deprivation ◽  
Sleep Schedule

Abstract Introduction Adequate cardiorespiratory fitness is of utmost importance during spaceflight and should be assessable via moderate work rate intensities, e.g., using kinetics parameters. The combination of restricted sleep, and defined physical exercise during a 45-day simulated space mission is expected to slow heart rate (HR) kinetics without changes in oxygen uptake ($${\dot{\text{V}}\text{O}}_{{2}}$$ V ˙ O 2 ) kinetics. Methods Overall, 14 crew members (9 males, 5 females, 37 ± 7 yrs, 23.4 ± 3.5 kg m−2) simulated a 45-d-mission to an asteroid. During the mission, the sleep schedule included 5 nights of 5 h and 2 nights of 8 h sleep. The crew members were tested on a cycle ergometer, using pseudo-random binary sequences, changing between 30 and 80 W on day 8 before (MD-8), day 22 (MD22) and 42 (MD42) after the beginning and day 4 (MD + 4) following the end of the mission. Kinetics information was assessed using the maxima of cross-correlation functions (CCFmax). Higher CCFmax indicates faster responses. Results CCFmax(HR) was significantly (p = 0.008) slower at MD-8 (0.30 ± 0.06) compared with MD22 (0.36 ± 0.06), MD42 (0.38 ± 0.06) and MD + 4 (0.35 ± 0.06). Mean HR values during the different work rate steps were higher at MD-8 and MD + 4 compared to MD22 and MD42 (p < 0.001). Discussion The physical training during the mission accelerated HR kinetics, but had no impact on mean HR values post mission. Thus, HR kinetics seem to be sensitive to changes in cardiorespiratory fitness and may be a valuable parameter to monitor fitness. Kinetics and capacities adapt independently in response to confinement in combination with defined physical activity and sleep.

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