A phenomenological model of muscle fatigue and the power-endurance relationship

2012 ◽  
Vol 113 (10) ◽  
pp. 1643-1651 ◽  
Author(s):  
A. James ◽  
S. Green
Keyword(s):  
Phenomenological Model ◽  
Power Output ◽  
Goodness Of Fit ◽  
Maximal Exercise ◽  
Muscle Power ◽  
Motor Units ◽  
Time Profile ◽  
Human Power ◽  
Power Outputs ◽  
The Relationship

The relationship between power output and the time that it can be sustained during exercise (i.e., endurance) at high intensities is curvilinear. Although fatigue is implicit in this relationship, there is little evidence pertaining to it. To address this, we developed a phenomenological model that predicts the temporal response of muscle power during submaximal and maximal exercise and which was based on the type, contractile properties (e.g., fatiguability), and recruitment of motor units (MUs) during exercise. The model was first used to predict power outputs during all-out exercise when fatigue is clearly manifest and for several distributions of MU type. The model was then used to predict times that different submaximal power outputs could be sustained for several MU distributions, from which several power-endurance curves were obtained. The model was simultaneously fitted to two sets of human data pertaining to all-out exercise (power-time profile) and submaximal exercise (power-endurance relationship), yielding a high goodness of fit ( R2 = 0.96–0.97). This suggested that this simple model provides an accurate description of human power output during submaximal and maximal exercise and that fatigue-related processes inherent in it account for the curvilinearity of the power-endurance relationship.

Design and Evaluation of a Modified Underwater Cycle Ergometer

1996 ◽  
Vol 21 (2) ◽  
pp. 134-148 ◽  
Author(s):  
An A. Chen ◽  
Glen P. Kenny ◽  
Chad E. Johnston ◽  
Gordon G. Giesbrecht
Keyword(s):  
Power Output ◽  
Maximal Exercise ◽  
Exercise Duration ◽  
Cycle Ergometer ◽  
Gear Ratio ◽  
Upright Position ◽  
Exercise Tests ◽  
Maximal Power Output ◽  
Power Outputs ◽  
Key Words Core Temperature

An underwater cycle ergometer was designed consisting of an aluminum cycle frame in water connected with a 1:1 gear ratio to a mechanically braked standard cycle ergometer supported above the water. Three progressive maximal exercise tests were performed (n = 10): (a) the underwater ergometer in water (UEW), (b) underwater ergometer in air (UEA), and (c) a standard cycle ergometer in air (SEA). At submaximal power outputs, oxygen consumption [Formula: see text] and heart rate (HR) were generally lower in the SEA condition (p <.05), indicating that exercise in the upright position was more efficient. Exercise in water (UEW) resulted in lower total exercise duration, maximal HR, and maximal Tes than in air conditions. The upright position (SEA) resulted in greater total exercise duration and maximal power output than the semirecumbent positions. Because of positional differences between the standard and underwater ergometers, air-water comparisons should be made by using the underwater ergometer in water and on land. Key words: core temperature, esophageal temperature, skin temperature, exercise, resistance, work, power output, heat balance, heat loss, heat production, thermoregulation

scholarly journals Muscle power output limits fast-start performance in fish.

1998 ◽  
Vol 201 (10) ◽  
pp. 1505-1526 ◽  
Author(s):  
J M Wakeling ◽  
I A Johnston
Keyword(s):  
Muscle Mass ◽  
Power Output ◽  
White Muscle ◽  
Muscle Power ◽  
Specific Power ◽  
Muscle Dynamics ◽  
Power Outputs ◽  
Work Loop ◽  
Muscle Power Output

Fast-starts associated with escape responses were filmed at the median habitat temperatures of six teleost fish: Notothenia coriiceps and Notothenia rossii (Antarctica), Myoxocephalus scorpius (North Sea), Scorpaena notata and Serranus cabrilla (Mediterranean) and Paracirrhites forsteri (Indo-West-Pacific Ocean). Methods are presented for estimating the spine positions for silhouettes of swimming fish. These methods were used to validate techniques for calculating kinematics and muscle dynamics during fast-starts. The starts from all species show common patterns, with waves of body curvature travelling from head to tail and increasing in amplitude. Cross-validation with sonomicrometry studies allowed gearing ratios between the red and white muscle to be calculated. Gearing ratios must decrease towards the tail with a corresponding change in muscle geometry, resulting in similar white muscle fibre strains in all the myotomes during the start. A work-loop technique was used to measure mean muscle power output at similar strain and shortening durations to those found in vivo. The fast Sc. notata myotomal fibres produced a mean muscle-mass-specific power of 142.7 W kg-1 at 20 degrees C. Velocity, acceleration and hydrodynamic power output increased both with the travelling rate of the wave of body curvature and with the habitat temperature. At all temperatures, the predicted mean muscle-mass-specific power outputs, as calculated from swimming sequences, were similar to the muscle power outputs measured from work-loop experiments.

Slow muscle power output of yellow- and silver-phase European eels (Anguilla anguilla L.): changes in muscle performance prior to migration

2001 ◽  
Vol 204 (7) ◽  
pp. 1369-1379 ◽  
Author(s):  
D.J. Ellerby ◽  
I.L. Spierts ◽  
J.D. Altringham
Keyword(s):  
Life History ◽  
Power Output ◽  
Muscle Power ◽  
Anguilla Anguilla ◽  
Slow Muscle ◽  
The Body ◽  
Body Axis ◽  
Power Outputs ◽  
Stimulus Offset ◽  
Muscle Power Output

Eels swim in the anguilliform mode in which the majority of the body axis undulates to generate thrust. For this reason, muscle function has been hypothesised to be relatively uniform along the body axis relative to some other teleosts in which the caudal fin is the main site of thrust production. The European eel (Anguilla anguilla L.) has a complex life cycle involving a lengthy spawning migration. Prior to migration, there is a metamorphosis from a yellow (non-migratory) to a silver (migratory) life-history phase. The work loop technique was used to determine slow muscle power outputs in yellow- and silver-phase eels. Differences in muscle properties and power outputs were apparent between yellow- and silver-phase eels. The mass-specific power output of silver-phase slow muscle was greater than that of yellow-phase slow muscle. Maximum slow muscle power outputs under approximated in vivo conditions were 0.24 W kg(−)(1) in yellow-phase eel and 0.74 W kg(−)(1) in silver-phase eel. Power output peaked at cycle frequencies of 0.3-0.5 Hz in yellow-phase slow muscle and at 0.5-0.8 Hz in silver-phase slow muscle. The time from stimulus offset to 90 % relaxation was significantly greater in yellow- than in silver-phase eels. The time from stimulus onset to peak force was not significantly different between life-history stages or axial locations. Yellow-phase eels shifted to intermittent bursts of higher-frequency tailbeats at a lower swimming speed than silver-phase eels. This may indicate recruitment of fast muscle at low speeds in yellow-phase eels to compensate for a relatively lower slow muscle power output and operating frequency.

Changes in Elbow Flexor Power with Intermittent Contractions and Various Loads

2008 ◽  
Vol 107 (2) ◽  
pp. 597-606
Author(s):  
Shunsuke Yamaji ◽  
Shinichi Demura ◽  
Hiroki Aoki ◽  
Kei Yamamoto
Keyword(s):  
Power Output ◽  
Peak Power ◽  
Muscle Power ◽  
Average Power ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Significant Difference ◽  
Average Power Output ◽  
Power Outputs ◽  
Intermittent Contractions

This study examined intermittent elbow flexion every 2 see. for 1 min. using various loads to study the properties of muscle power output and their relationship to peak power, defined as the maximum power output. 18 young men performed intermittent explosive elbow flexion (30 times × min.−1) using 30%, 40%, and 50% maximal voluntary contraction (MVC). The power outputs at 30% and 40% MVC slightly decreased (rate of decrease from peak power to average power output during the 26 to 30 contractions was about 5%). However, at 50% MVC, there was a marked decrease (33.6%). Power output for 8 contractions was significantly larger at 50% MVC than at 30% and 40% MVC, but after 9 contractions there was no significant difference between 40% and 50% MVC. In addition, after 27 contractions, 40% MVC was significantly larger than 30% and 50% MVC. That is, the tendency for power output to decrease differed among the various loads. The rate of decrease of power outputs showed no significant correlation with peak power for each load. Therefore, the rate of decrease or power output in intermittent contractions may help sustain the power output and cannot be evaluated as accurately as peak power.

The relationship between passive stiffness and muscle power output: Influence of muscle cross-sectional area normalization

2013 ◽  
Vol 49 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Ty B. Palmer ◽  
Nathaniel D.M. Jenkins ◽  
Brennan J. Thompson ◽  
Douglas B. Smith ◽  
Joel T. Cramer
Keyword(s):  
Power Output ◽  
Muscle Power ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Passive Stiffness ◽  
Cross Sectional ◽  
Muscle Cross Sectional Area ◽  
The Relationship ◽  
Muscle Power Output

Sex Differences of Intermittent Elbow Flexion Power Using Various Loads

2008 ◽  
Vol 107 (2) ◽  
pp. 629-642
Author(s):  
Shunsuke Yamaji ◽  
Shinichi Demura ◽  
Kei Yamamoto
Keyword(s):  
Sex Difference ◽  
Power Output ◽  
Peak Power ◽  
Muscle Power ◽  
Elbow Flexion ◽  
Young Males ◽  
Significant Difference ◽  
Power Outputs ◽  
Increasing Load ◽  
Load Mass

This study was designed to clarity a sex difference in muscle power output properties by intermittent elbow flexion using various loads. 10 young males and 10 young females performed intermittent elbow flexion power outputs at 30 times × min.−1 for 1 min. using 30%, 40%, and 50% MVC loads. For both sexes, the decreasing peak power showed a similar trend between trials at all loads, and the reliability of each power parameter was good. The power outputs decreased largely with increasing load mass, and the power output in 50% MVC for males markedly decreased to the same level as that during the final phase in 30% MVC. Although the absolute value of regression coefficients for males became significantly larger with increasing load mass, that for females showed a significant difference only between 30% and 50% MVC. In 50% MVC, a large decrease for males was observed. Maximal peak power outputs were significantly larger with increasing load mass for both sexes, but for males more than for females. In both sexes, there were no significant differences among final powers of each load mass, and between total powers of 40% and 50% MVC. For the sum of every 5 consecutive power outputs, males showed significant differences between 30% and 40% MVC in all periods after the 6th contraction, but females did not and also between 30% and 50%. MVC in periods after the 16th contraction. In conclusion, it is considered that power outputs in the latter phases in 50% MVC are affected largely by muscle fatigue, and an intermittent power output test with 50% MVC can measure sustained power (fatigue resistance) in the latter phases, but there is a sex difference in the tendency to decrease.

scholarly journals Evolutionary adaptation of contractile performance in muscle of ectothermic winter-flying moths

1995 ◽  
Vol 198 (10) ◽  
pp. 2087-2094 ◽  
Author(s):  
J Marden
Keyword(s):  
Power Output ◽  
Muscle Activation ◽  
Muscle Power ◽  
Flight Muscle ◽  
Thermal Sensitivity ◽  
Muscle Performance ◽  
Shortening Velocity ◽  
Instantaneous Power ◽  
Generating Capacity ◽  
Power Outputs

The temperature-sensitivity of muscle performance in a winter-flying ecotothermic moth (Operophtera bruceata) was examined and compared with that of a summer-flying endothermic hawkmoth (Manduca sexta). O. bruceata muscle contracted over a temperature range of 1&shy;28 &deg;C, whereas M. sexta muscle contracted at temperatures of 13&shy;42.5 &deg;C. Maximum (unloaded) contraction velocity (Vmax) was greater in O. bruceata over most of the range of temperatures where muscle from both species was excitable (3&shy;4 lengths s-1 versus 0.6&shy;3.6 lengths s-1 at 13&shy;28 &deg;C), but M. sexta muscle achieved a much higher Vmax at the temperature that this species maintains during flight (10 lengths s-1 at 40&shy;42.5 &deg;C). The capacity of O. bruceata muscle to generate tension was approximately twice that of M. sexta muscle (peak tetanic tension of 13.9 versus 7.0 N cm-2). This greater force-generating capacity in O. bruceata largely offset its lower shortening velocity, such that maximum instantaneous power output was equivalent in both species at temperatures below 35 &deg;C (approximately 100&shy;120 W kg-1). M. sexta muscle achieved instantaneous power outputs of up to 202 W kg-1 at temperatures of 40&shy;42.5 &deg;C. Muscle activation and deactivation (measured by times to peak tension and to half-relaxation during isometric twitches) were most rapid for O. bruceata at temperatures of 15&shy;30 &deg;C and for M. sexta at temperatures of 30&shy;40 &deg;C. Data for power output of flight muscle from these moths are combined with estimates of induced power required for flight in order to show how adaptations for thermal sensitivity of muscle power output interact with morphology (low wing-loading, high flight muscle ratio) to allow O. bruceata moths to fly at extremely low body temperatures, and to construct a model showing how the fecundity of flightless O. bruceata females would decline if they were to regain the ability to fly. Marginal flight over a narrow range of temperatures for O. bruceata females would require a 17 % reduction in fecundity; to fly over as large a range of temperatures as do males would require an 82 % reduction in fecundity.

scholarly journals Why is the force-velocity relationship in leg press tasks quasi-linear rather than hyperbolic?

2012 ◽  
Vol 112 (12) ◽  
pp. 1975-1983 ◽  
Author(s):  
Maarten F. Bobbert
Keyword(s):  
External Force ◽  
Power Output ◽  
Muscle Force ◽  
Muscle Power ◽  
Leg Length ◽  
Leg Extension ◽  
Leg Press ◽  
Velocity Relationship ◽  
Force Velocity ◽  
The Relationship

Force-velocity relationships reported in the literature for functional tasks involving a combination of joint rotations tend to be quasi-linear. The purpose of this study was to explain why they are not hyperbolic, like Hill's relationship. For this purpose, a leg press task was simulated with a musculoskeletal model of the human leg, which had stimulation of knee extensor muscles as only independent input. In the task the ankles moved linearly, away from the hips, against an imposed external force that was reduced over contractions from 95 to 5% of the maximum isometric value. Contractions started at 70% of leg length, and force and velocity values were extracted when 80% of leg length was reached. It was shown that the relationship between leg extension velocity and external force was quasi-linear, while the relationship between leg extension velocity and muscle force was hyperbolic. The discrepancy was explained by the fact that segmental dynamics canceled more and more of the muscle force as the external force was further reduced and velocity became higher. External power output peaked when the imposed external force was ∼50% of maximum, while muscle power output peaked when the imposed force was only ∼15% of maximum; in the latter case ∼70% of muscle power was buffered by the leg segments. According to the results of this study, there is no need to appeal to neural mechanisms to explain why, in leg press tasks, the force-velocity relationship is quasi-linear rather than hyperbolic.

Anaerobic threshold, blood lactate, and muscle metabolites in progressive exercise

1983 ◽  
Vol 54 (4) ◽  
pp. 1032-1038 ◽  
Author(s):  
H. J. Green ◽  
R. L. Hughson ◽  
G. W. Orr ◽  
D. A. Ranney
Keyword(s):  
Blood Lactate ◽  
Anaerobic Threshold ◽  
Power Output ◽  
Vastus Lateralis ◽  
Muscle Metabolism ◽  
Ventilatory Anaerobic Threshold ◽  
Progressive Exercise ◽  
Power Outputs ◽  
The Relationship

The purpose of this study was to investigate the interrelationship between the ventilatory anaerobic threshold (VAT), the blood lactate anaerobic threshold (LAT), and the alteration in muscle metabolism. Ten subjects (5 men and 5 women) performed progressive exercise to exhaustion on two occasions for determination of the VAT and the LAT. For both AT criteria, the initial breakpoints (P less than 0.05) in the relationship between ventilation (VE) and O2 uptake (VO2VAT) and lactate (La) and power output (POLAT) were determined by multisegmental linear regression. During three subsequent tests the subjects performed progressive exercise to various percentages of the VO2VAT. Biopsies were obtained from the musculus vastus lateralis for determination of selected glycolytic intermediates at the cessation of exercise. It was found that the VO2VAT, expressed in terms of power output (POVAT), occurred at a higher value (P less than 0.05) than the POLAT (1,004 vs. 621 kg X min-1). Blood La values at these power outputs were 2.09 and 1.25 mM, respectively. Determination of the muscle La concentration at 79, 94, and 110% of VO2VAT indicated significant increases (P less than 0.05) from rest values of 1.59 to 4.49, 6.37, and 11.3 mmol X kg wet wt-1, respectively. It is concluded that the gas exchange AT as determined by the relationship between VE and VO2VAT and the AT as determined by blood La accumulation (LAT) are not coincidental. In addition the elevation in muscle anaerobic glycolysis precedes both the VAT and the blood LAT in this progressive exercise test.

Sign in / Sign up

Export Citation Format

Share Document