Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement

1997 ◽  
Vol 83 (5) ◽  
pp. 1749-1755 ◽  
Author(s):  
Yudai Takarada ◽  
Yuichi Hirano ◽  
Yusuke Ishige ◽  
Naokata Ishii
Keyword(s):  
Power Output ◽  
Inverse Dynamics ◽  
Vastus Lateralis ◽  
Reaction Force ◽  
The Body ◽  
Mechanical Power ◽  
Mean Power ◽  
Mechanical Power Output ◽  
Muscle Moments ◽  
Power Outputs

Takarada, Yudai, Yuichi Hirano, Yusuke Ishige, and Naokata Ishii. Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement. J. Appl. Physiol. 83(5): 1749–1755, 1997.—The relation between the eccentric force developed during a countermovement and the mechanical power output was studied in squatting exercises under nominally isotonic load (50% of 1-repetition maximum). The subjects ( n = 5) performed squatting exercises with a countermovement at varied deceleration rates before lifting the load. The ground reaction force and video images were recorded to obtain the power output of the body. Net muscle moments acting at hip, knee, and ankle joints were calculated from video recordings by using inverse dynamics. When an intense deceleration was taken at the end of downward movement, large eccentric force was developed, and the mechanical power subsequently produced during the lifting movement was consistently larger than that produced without the countermovement. Both maximal and mean power outputs during concentric actions increased initially with the eccentric force, whereas they began to decline when the eccentric force exceeded ∼1.4 times the sum of load and body weight. Video-image analysis showed that this characteristic relation was predominantly determined by the torque around the knee joint. Electromyographic analyses showed no consistent increase in time-averaged integrated electromyograph from vastus lateralis with the power output, suggesting that the enhancement of power output is primarily caused by the prestretch-induced improvement of an intrinsic force-generating capability of the agonist muscle.

Sprint performance-duration relationships are set by the fractional duration of external force application

2006 ◽  
Vol 290 (3) ◽  
pp. R758-R765 ◽  
Author(s):  
Peter G. Weyand ◽  
Jennifer E. Lin ◽  
Matthew W. Bundle
Keyword(s):  
Power Output ◽  
Time Course ◽  
Constant Load ◽  
Mechanical Power ◽  
Mean Power ◽  
Force Application ◽  
Mechanical Power Output ◽  
Sprint Cycling ◽  
Power Outputs ◽  
Single Exponential

We hypothesized that the maximum mechanical power outputs that can be maintained during all-out sprint cycling efforts lasting from a few seconds to several minutes can be accurately estimated from a single exponential time constant ( kcycle) and two measurements on individual cyclists: the peak 3-s power output (Pmech max) and the maximum mechanical power output that can be supported aerobically (Paer). Tests were conducted on seven subjects, four males and three females, on a stationary cycle ergometer at a pedal frequency of 100 rpm. Peak mechanical power output (Pmech max) was the highest mean power output attained during a 3-s burst; the maximum power output supported aerobically (Paer) was determined from rates of oxygen uptake measured during a progressive, discontinuous cycling test to failure. Individual power output-duration relationships were determined from 13 to 16 all-out constant load sprints lasting from 5 to 350 s. In accordance with the above hypothesis, the power outputs measured during all-out sprinting efforts were estimated to within an average of 34 W or 6.6% from Pmech max, Paer, and a single exponential constant ( kcycle = 0.026 s−1) across a sixfold range of power outputs and a 70-fold range of sprint trial durations ( R2 = 0.96 vs. identity, n = 105; range: 180 to 1,136 W). Duration-dependent decrements in sprint cycling power outputs were two times greater than those previously identified for sprint running speed ( krun = 0.013 s−1). When related to the respective times of pedal and ground force application rather than total sprint time, decrements in sprint cycling and running performance followed the same time course ( k = 0.054 s−1). We conclude that the duration-dependent decrements in sprinting performance are set by the fractional duration of the relevant muscular contractions.

Contrast Loading: Power Output and Rest Interval Effects on Neuromuscular Performance

2014 ◽  
Vol 9 (3) ◽  
pp. 567-574
Author(s):  
Konstantinos Sotiropoulos ◽  
Ilias Smilios ◽  
Helen Douda ◽  
Marios Christou ◽  
Savvas P. Tokmakidis
Keyword(s):  
Power Output ◽  
Training Session ◽  
Mechanical Power ◽  
Emg Activity ◽  
Rest Interval ◽  
Mechanical Power Output ◽  
Squat Exercise ◽  
Power Outputs ◽  
And Control ◽  
Time Point

Purpose:This study examined the effect of rest interval after the execution of a jump-squat set with varied external mechanical-power outputs on repeated-jump (RJ) height, mechanical power, and electromyographic (EMG) activity.Methods:Twelve male volleyball players executed 6 RJs before and 1, 3, 5, 7, and 10 min after the execution of 6 repetitions of jump squats with a load: maximized mechanical-power output (Pmax), 70% of Pmax, 130% of Pmax, and control, without extra load.Results:RJ height did not change (P = .44) after the jump squats, mechanical power was higher (P = .02) 5 min after the 130%Pmax protocol, and EMG activity was higher (P = .001) after all exercise protocols compared with control. Irrespective of the time point, however, when the highest RJ set for each individual was analyzed, height, mechanical power, and EMG activity were higher (P = .001–.04) after all loading protocols compared with control, with no differences observed (P = .53–.72) among loads.Conclusions:Rest duration for a contrast-training session should be individually determined regardless of the load and mechanical-power output used to activate the neuromuscular system. The load that maximizes external mechanical-power output compared with a heavier or a lighter load, using the jump-squat exercise, is not more effective for increasing jumping performance afterward.

Maximum speed and mechanical power output in lizards.

1997 ◽  
Vol 200 (16) ◽  
pp. 2189-2195 ◽  
Author(s):  
C T Farley
Keyword(s):  
Body Mass ◽  
Power Output ◽  
Center Of Mass ◽  
The Body ◽  
Mechanical Power ◽  
Stride Frequency ◽  
Maximum Speed ◽  
Muscular System ◽  
Running Speed ◽  
Mechanical Power Output

The goal of the present study was to test the hypothesis that maximum running speed is limited by how much mechanical power the muscular system can produce. To test this hypothesis, two species of lizards, Coleonyx variegatus and Eumeces skiltonianus, sprinted on hills of different slopes. According to the hypothesis, maximum speed should decrease on steeper uphill slopes but mechanical power output at maximum speed should be independent of slope. For level sprinting, the external mechanical power output was determined from force platform data. For uphill sprinting, the mechanical power output was approximated as the power required to lift the center of mass vertically. When the slope increased from level to 40 degrees uphill, maximum speed decreased by 28% in C. variegatus and by 16% in E. skiltonianus. At maximum speed on a 40 degrees uphill slope in both species, the mechanical power required to lift the body vertically was approximately 3.9 times greater than the external mechanical power output at maximum speed on the level. Because total limb mass is small in both species (6-16% of body mass) and stride frequency is similar at maximum speed on all slopes, the internal mechanical power output is likely to be small and similar in magnitude on all slopes. I conclude that the muscular system is capable of producing substantially more power during locomotion than it actually produces during level sprinting. Thus, the capacity of the muscular system to produce power does not limit maximum running speed.

scholarly journals Tuna robotics: hydrodynamics of rapid linear accelerations

2021 ◽  
Vol 288 (1945) ◽  
pp. 20202726
Author(s):  
Robin Thandiackal ◽  
Carl H. White ◽  
Hilary Bart-Smith ◽  
George V. Lauder
Keyword(s):  
Power Consumption ◽  
Power Output ◽  
Beat Frequency ◽  
Electrical Power ◽  
Particle Image Velocimetry Data ◽  
The Body ◽  
Mechanical Power ◽  
Caudal Fin ◽  
Mechanical Power Output ◽  
Electrical Power Consumption

Fish routinely accelerate during locomotor manoeuvres, yet little is known about the dynamics of acceleration performance. Thunniform fish use their lunate caudal fin to generate lift-based thrust during steady swimming, but the lift is limited during acceleration from rest because required oncoming flows are slow. To investigate what other thrust-generating mechanisms occur during this behaviour, we used the robotic system termed Tunabot Flex, which is a research platform featuring yellowfin tuna-inspired body and tail profiles. We generated linear accelerations from rest of various magnitudes (maximum acceleration of 3.22   m   s − 2 at 11.6   Hz tail beat frequency) and recorded instantaneous electrical power consumption. Using particle image velocimetry data, we quantified body kinematics and flow patterns to then compute surface pressures, thrust forces and mechanical power output along the body through time. We found that the head generates net drag and that the posterior body generates significant thrust, which reveals an additional propulsion mechanism to the lift-based caudal fin in this thunniform swimmer during linear accelerations from rest. Studying fish acceleration performance with an experimental platform capable of simultaneously measuring electrical power consumption, kinematics, fluid flow and mechanical power output provides a new opportunity to understand unsteady locomotor behaviours in both fishes and bioinspired aquatic robotic systems.

scholarly journals DRAG AND LIFT ON RUNNING INSECTS

1993 ◽  
Vol 176 (1) ◽  
pp. 89-101 ◽  
Author(s):  
R. J. Full ◽  
M. A. R. Koehl
Keyword(s):  
Power Output ◽  
Periplaneta Americana ◽  
Aerodynamic Drag ◽  
The Body ◽  
Mechanical Power ◽  
Kinematic Data ◽  
Blaberus Discoidalis ◽  
Flying Insects ◽  
Mechanical Power Output ◽  
Drag And Lift

We examined the effects of aerodynamic forces on the mechanical power output of running insects for which kinematic data were available. Drag and lift on the cockroaches Periplaneta americana (a small, rapidly running species) and Blaberus discoidalis (a larger, more slowly moving species) were measured in a wind tunnel. Although lift would be expected to affect power output by altering functional body weight, the magnitude of the lift on these cockroaches was less than 2 % of their weight. Drag, which increases the horizontal force that must be exerted to run at a given speed, accounted for 20–30 % of the power output of P. americana running at speeds of 1.0-1.5 m s-1, but had a much smaller effect on B. discoidalis. Aerodynamic drag on the body (parasite drag) can significantly increase the mechanical power output necessary for small, rapidly running insects in contrast to larger running animals and to flying insects.

scholarly journals Determinants of metabolic cost during submaximal cycling

2002 ◽  
Vol 93 (3) ◽  
pp. 823-828 ◽  
Author(s):  
J. McDaniel ◽  
J. L. Durstine ◽  
G. A. Hand ◽  
J. C. Martin
Keyword(s):  
Power Output ◽  
Muscle Activation ◽  
Metabolic Cost ◽  
Mechanical Power ◽  
Shortening Velocity ◽  
Mechanical Power Output ◽  
Muscle Shortening ◽  
Main Determinants ◽  
Power Outputs ◽  
Pedaling Rate

The metabolic cost of producing submaximal cycling power has been reported to vary with pedaling rate. Pedaling rate, however, governs two physiological phenomena known to influence metabolic cost and efficiency: muscle shortening velocity and the frequency of muscle activation and relaxation. The purpose of this investigation was to determine the relative influence of those two phenomena on metabolic cost during submaximal cycling. Nine trained male cyclists performed submaximal cycling at power outputs intended to elicit 30, 60, and 90% of their individual lactate threshold at four pedaling rates (40, 60, 80, 100 rpm) with three different crank lengths (145, 170, and 195 mm). The combination of four pedaling rates and three crank lengths produced 12 pedal speeds ranging from 0.61 to 2.04 m/s. Metabolic cost was determined by indirect calorimetery, and power output and pedaling rate were recorded. A stepwise multiple linear regression procedure selected mechanical power output, pedal speed, and pedal speed squared as the main determinants of metabolic cost ( R 2 = 0.99 ± 0.01). Neither pedaling rate nor crank length significantly contributed to the regression model. The cost of unloaded cycling and delta efficiency were 150 metabolic watts and 24.7%, respectively, when data from all crank lengths and pedal speeds were included in a regression. Those values increased with increasing pedal speed and ranged from a low of 73 ± 7 metabolic watts and 22.1 ± 0.3% (145-mm cranks, 40 rpm) to a high of 297 ± 23 metabolic watts and 26.6 ± 0.7% (195-mm cranks, 100 rpm). These results suggest that mechanical power output and pedal speed, a marker for muscle shortening velocity, are the main determinants of metabolic cost during submaximal cycling, whereas pedaling rate (i.e., activation-relaxation rate) does not significantly contribute to metabolic cost.

Mechanical power output during running accelerations in wild turkeys

2002 ◽  
Vol 205 (10) ◽  
pp. 1485-1494 ◽  
Author(s):  
Thomas J. Roberts ◽  
Jeffrey A. Scales
Keyword(s):  
Power Output ◽  
Ground Reaction Force ◽  
Center Of Mass ◽  
Reaction Force ◽  
Mechanical Power ◽  
Force Vector ◽  
Instantaneous Power ◽  
Hindlimb Muscle ◽  
Wild Turkeys ◽  
Running Mechanics

SUMMARYWe tested the hypothesis that the hindlimb muscles of wild turkeys(Meleagris gallopavo) can produce maximal power during running accelerations. The mechanical power developed during single running steps was calculated from force-plate and high-speed video measurements as turkeys accelerated over a trackway. Steady-speed running steps and accelerations were compared to determine how turkeys alter their running mechanics from a low-power to a high-power gait. During maximal accelerations, turkeys eliminated two features of running mechanics that are characteristic of steady-speed running: (i) they produced purely propulsive horizontal ground reaction forces, with no braking forces, and (ii) they produced purely positive work during stance, with no decrease in the mechanical energy of the body during the step. The braking and propulsive forces ordinarily developed during steady-speed running are important for balance because they align the ground reaction force vector with the center of mass. Increases in acceleration in turkeys correlated with decreases in the angle of limb protraction at toe-down and increases in the angle of limb retraction at toe-off. These kinematic changes allow turkeys to maintain the alignment of the center of mass and ground reaction force vector during accelerations when large propulsive forces result in a forward-directed ground reaction force. During the highest accelerations, turkeys produced exclusively positive mechanical power. The measured power output during acceleration divided by the total hindlimb muscle mass yielded estimates of peak instantaneous power output in excess of 400 W kg-1 hindlimb muscle mass. This value exceeds estimates of peak instantaneous power output of turkey muscle fibers. The mean power developed during the entire stance phase increased from approximately zero during steady-speed runs to more than 150 W kg-1muscle during the highest accelerations. The high power outputs observed during accelerations suggest that elastic energy storage and recovery may redistribute muscle power during acceleration. Elastic mechanisms may expand the functional range of muscle contractile elements in running animals by allowing muscles to vary their mechanical function from force-producing struts during steady-speed running to power-producing motors during acceleration.

scholarly journals Effect of Accommodating Elastic Bands on Mechanical Power Output during Back Squats

Sports ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 151 ◽  
Author(s):  
Takafumi Kubo ◽  
Kuniaki Hirayama ◽  
Nobuhiro Nakamura ◽  
Mitsuru Higuchi
Keyword(s):  
Power Output ◽  
Random Order ◽  
Mechanical Power ◽  
Muscular Force ◽  
Force Output ◽  
Elastic Band ◽  
Free Weight ◽  
Mechanical Power Output ◽  
Elastic Bands ◽  
Acceleration And Deceleration

The aim of this study was to investigate whether accommodating elastic bands with barbell back squats (BSQ) increase muscular force during the deceleration subphase. Ten healthy men (mean ± standard deviation: Age: 23 ± 2 years; height: 170.5 ± 3.7 cm; mass: 66.7 ± 5.4 kg; and BSQ one repetition maximum (RM): 105 ± 23.1 kg; BSQ 1RM/body mass: 1.6 ± 0.3) were recruited for this study. The subjects performed band-resisted parallel BSQ (accommodating elastic bands each sides of barbell) with five band conditions in random order. The duration of the deceleration subphase, mean mechanical power, and the force and velocity during the acceleration and deceleration subphases were calculated. BSQ with elastic bands elicited greater mechanical power output, velocity, and force during the deceleration subphase, in contrast to that elicited with traditional free weight (p < 0.05). BSQ with elastic bands also elicited greater mechanical power output and velocity during the acceleration subphase. However, the force output during the acceleration subphase using an elastic band was lesser than that using a traditional free weight (p < 0.05). This study suggests that BSQ with elastic band elicit greater power output during the acceleration and deceleration subphases.

Pinacidil-primed ATP-sensitive potassium channels mediate feedback control of mechanical power output in isolated myocardium of rats and guinea pigs

2010 ◽  
Vol 628 (1-3) ◽  
pp. 116-127 ◽  
Author(s):  
Diethart Schmid ◽  
Dawid L. Staudacher ◽  
Christian A. Plass ◽  
Hans G. Loew ◽  
Eva Fritz ◽  
...  
Keyword(s):  
Feedback Control ◽  
Potassium Channels ◽  
Power Output ◽  
Guinea Pigs ◽  
Mechanical Power ◽  
Mechanical Power Output ◽  
Isolated Myocardium
Sign in / Sign up

Export Citation Format

Share Document