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.

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.

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.

scholarly journals The effect of cycling shoes and the shoe-pedal interface on maximal mechanical power output in bicycling

2019 ◽  
Author(s):  
Andrew Christopher Burns ◽  
Rodger Kram
Keyword(s):  
Scientific Evidence ◽  
Metabolic Cost ◽  
Cycling Performance ◽  
Maximum Power ◽  
Mechanical Power ◽  
Mechanical Power Output ◽  
Running Shoes ◽  
Longitudinal Bending ◽  
Sprint Cycling ◽  
Power Outputs

Cyclists and industry professionals believe that cycling shoes improve performance. However, scientific evidence has demonstrated that cycling shoes have no significant effect on metabolic cost during submaximal, steady-state cycling (50-150 W). Here, we investigated if cycling shoes and click-in pedals provide benefits relevant to sprint cycling. We measured the mechanical power outputs and velocities of twelve healthy male participants during maximal sprint cycling with the null hypotheses of no differences. Participants rode outdoors on a paved asphalt road with a steady, uphill gradient of 4.9%. Each participant completed sets of three 100-meter cycling sprints in three conditions: (1) running shoes with flat pedals, (2) running shoes with classic aluminium quill pedals with toe clips and straps, and (3) rigid-soled, cleated cycling shoes with click-in pedals. Average and maximal power outputs and velocities all increased with the addition of a shoe-pedal attachment and further increased with the stiff soles. When using the running shoes, the toe clip attachment increased maximum power by 9.7 +/- 8.7% (p=1.7E-03). Comparing the running shoes with toe clips versus cycling shoes with click-in pedals conditions, the greater longitudinal bending stiffness of the cycling shoes enhanced maximum power by 16.6 +/- 10.2% (p=3.25E-06). Hence, we reject both null hypotheses. Shoe-pedal attachment and stiff soles independently and positively improve cycling performance during high-power, uphill sprints.

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.

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.

scholarly journals The Ingestion of 39 or 64 g·hr−1 of Carbohydrate is Equally Effective at Improving Endurance Exercise Performance in Cyclists

2015 ◽  
Vol 25 (3) ◽  
pp. 285-292 ◽  
Author(s):  
Michael L. Newell ◽  
Angus M. Hunter ◽  
Claire Lawrence ◽  
Kevin D. Tipton ◽  
Stuart D. R. Galloway
Keyword(s):  
Power Output ◽  
Statistical Significance ◽  
Time Trial ◽  
Cycling Performance ◽  
Constant Load ◽  
Peak Power Output ◽  
Task Completion ◽  
Intake Rate ◽  
Mean Power ◽  
Pacing Strategy

In an investigator-blind, randomized cross-over design, male cyclists (mean± SD) age 34.0 (± 10.2) years, body mass 74.6 (±7.9) kg, stature 178.3 (±8.0) cm, peak power output (PPO) 393 (±36) W, and VO2max 62 (±9) ml·kg−1min−1 training for more than 6 hr/wk for more than 3y (n = 20) completed four experimental trials. Each trial consisted of a 2-hr constant load ride at 95% of lactate threshold (185 ± 25W) then a work-matched time trial task (~30min at 70% of PPO). Three commercially available carbohydrate (CHO) beverages, plus a control (water), were administered during the 2-hr ride providing 0, 20, 39, or 64g·hr−1 of CHO at a fluid intake rate of 1L·hr−1. Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39g·hr−1 (34:19.5 ± 03:07.1, p = .006) and 64g·hr−1 (34:11.3 ± 03:08.5 p = .004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was −6.1% (95% CI: −11.3 to −1.0) and −6.5% (95% CI: −11.7 to −1.4) in the 39 and 64g·hr−1 trials respectively. The 20g·hr−1 (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared with control (p = .126) despite a mean improvement of −3.7% (95% CI −8.8−1.5%). No further differences between CHO trials were reported. No interaction between CHO dose and pacing strategy occurred. 39 and 64g·hr−1 of CHO were similarly effective at improving endurance cycling performance compared with a 0g·hr−1 control in our trained cyclists.

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

Power output by an asynchronous flight muscle from a beetle

2000 ◽  
Vol 203 (17) ◽  
pp. 2667-2689 ◽  
Author(s):  
R.K. Josephson ◽  
J.G. Malamud ◽  
D.R. Stokes
Keyword(s):  
Power Output ◽  
Flight Muscle ◽  
Muscle Length ◽  
Mechanical Power ◽  
Effect Of Temperature ◽  
Muscle Temperature ◽  
Work Output ◽  
Stroke Frequency ◽  
Mechanical Power Output ◽  
Wing Stroke

The basalar muscle of the beetle Cotinus mutabilis is a large, fibrillar flight muscle composed of approximately 90 fibers. The paired basalars together make up approximately one-third of the mass of the power muscles of flight. Changes in twitch force with changing stimulus intensity indicated that a basalar muscle is innervated by at least five excitatory axons and at least one inhibitory axon. The muscle is an asynchronous muscle; during normal oscillatory operation there is not a 1:1 relationship between muscle action potentials and contractions. During tethered flight, the wing-stroke frequency was approximately 80 Hz, and the action potential frequency in individual motor units was approximately 20 Hz. As in other asynchronous muscles that have been examined, the basalar is characterized by high passive tension, low tetanic force and long twitch duration. Mechanical power output from the basalar muscle during imposed, sinusoidal strain was measured by the work-loop technique. Work output varied with strain amplitude, strain frequency, the muscle length upon which the strain was superimposed, muscle temperature and stimulation frequency. When other variables were at optimal values, the optimal strain for work per cycle was approximately 5%, the optimal frequency for work per cycle approximately 50 Hz and the optimal frequency for mechanical power output 60–80 Hz. Optimal strain decreased with increasing cycle frequency and increased with muscle temperature. The curve relating work output and strain was narrow. At frequencies approximating those of flight, the width of the work versus strain curve, measured at half-maximal work, was 5% of the resting muscle length. The optimal muscle length for work output was shorter than that at which twitch and tetanic tension were maximal. Optimal muscle length decreased with increasing strain. The curve relating work output and muscle length, like that for work versus strain, was narrow, with a half-width of approximately 3 % at the normal flight frequency. Increasing the frequency with which the muscle was stimulated increased power output up to a plateau, reached at approximately 100 Hz stimulation frequency (at 35 degrees C). The low lift generated by animals during tethered flight is consistent with the low frequency of muscle action potentials in motor units of the wing muscles. The optimal oscillatory frequency for work per cycle increased with muscle temperature over the temperature range tested (25–40 degrees C). When cycle frequency was held constant, the work per cycle rose to an optimum with increasing temperature and then declined. We propose that there is a temperature optimum for work output because increasing temperature increases the shortening velocity of the muscle, which increases the rate of positive work output during shortening, but also decreases the durations of the stretch activation and shortening deactivation that underlie positive work output, the effect of temperature on shortening velocity being dominant at lower temperatures and the effect of temperature on the time course of activation and deactivation being dominant at higher temperatures. The average wing-stroke frequency during free flight was 94 Hz, and the thoracic temperature was 35 degrees C. The mechanical power output at the measured values of wing-stroke frequency and thoracic temperature during flight, and at optimal muscle length and strain, averaged 127 W kg(−1)muscle, with a maximum value of 200 W kg(−1). The power output from this asynchronous flight muscle was approximately twice that measured with similar techniques from synchronous flight muscle of insects, supporting the hypothesis that asynchronous operation has been favored by evolution in flight systems of different insect groups because it allows greater power output at the high contraction frequencies of flight.

scholarly journals Total power output generated during dynamic knee extensor exercise at different contraction frequencies

2000 ◽  
Vol 89 (5) ◽  
pp. 1912-1918 ◽  
Author(s):  
Richard A. Ferguson ◽  
Per Aagaard ◽  
Derek Ball ◽  
Anthony J. Sargeant ◽  
Jens Bangsbo
Keyword(s):  
Power Output ◽  
Accurate Determination ◽  
Knee Extensor ◽  
Mechanical Efficiency ◽  
Muscle Group ◽  
Total Power ◽  
Mechanical Power Output ◽  
External Power ◽  
Power Outputs ◽  
Total Power Output

A novel approach has been developed for the quantification of total mechanical power output produced by an isolated, well-defined muscle group during dynamic exercise in humans at different contraction frequencies. The calculation of total power output comprises the external power delivered to the ergometer (i.e., the external power output setting of the ergometer) and the “internal” power generated to overcome inertial and gravitational forces related to movement of the lower limb. Total power output was determined at contraction frequencies of 60 and 100 rpm. At 60 rpm, the internal power was 18 ± 1 W (range: 16–19 W) at external power outputs that ranged between 0 and 50 W. This was less ( P < 0.05) than the internal power of 33 ± 2 W (27–38 W) at 100 rpm at 0–50 W. Moreover, at 100 rpm, internal power was lower ( P < 0.05) at the higher external power outputs. Pulmonary oxygen uptake was observed to be greater ( P< 0.05) at 100 than at 60 rpm at comparable total power outputs, suggesting that mechanical efficiency is lower at 100 rpm. Thus a method was developed that allowed accurate determination of the total power output during exercise generated by an isolated muscle group at different contraction frequencies.

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