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.

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.

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.

The effects of length trajectory on the mechanical power output of mouse skeletal muscles.

1997 ◽  
Vol 200 (24) ◽  
pp. 3119-3131 ◽  
Author(s):  
G N Askew ◽  
R L Marsh
Keyword(s):  
Strain Amplitude ◽  
Power Output ◽  
Maximum Power ◽  
Mechanical Power ◽  
Shortening Velocity ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Mechanical Power Output ◽  
Evolutionary Context

The effects of length trajectory on the mechanical power output of mouse soleus and extensor digitorum longus (EDL) muscles were investigated using the work loop technique in vitro at 37 degrees C. Muscles were subjected to sinusoidal and sawtooth cycles of lengthening and shortening; for the sawtooth cycles, the proportion of the cycle spent shortening was varied. For each cycle frequency examined, the timing and duration of stimulation and the strain amplitude were optimized to yield the maximum power output. During sawtooth length trajectories, power increased as the proportion of the cycle spent shortening increased. The increase in power was attributable to more complete activation of the muscle due to the longer stimulation duration, to a more rapid rise in force resulting from increased stretch velocity and to an increase in the optimal strain amplitude. The power produced during symmetrical sawtooth cycles was 5-10 % higher than during sinusoidal work loops. Maximum power outputs of 92 W kg-1 (soleus) and 247 W kg-1 (EDL) were obtained by manipulating the length trajectory. For each muscle, this was approximately 70 % of the maximum power output estimated from the isotonic force-velocity relationship. We have found a number of examples suggesting that animals exploit prolonging the shortening phase during activities requiring a high power output, such as flying, jet-propulsion swimming and vocalization. In an evolutionary context, increasing the relative shortening duration provides an alternative to increasing the maximum shortening velocity (Vmax) as a way to increase power output.

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 Mechanical Power output from Striated Muscle during Cyclic Contraction

1985 ◽  
Vol 114 (1) ◽  
pp. 493-512 ◽  
Author(s):  
Robert K. Josephson
Keyword(s):  
Power Output ◽  
Muscle Tension ◽  
Single Stimulus ◽  
Mechanical Power ◽  
Work Output ◽  
Shortening Velocity ◽  
Cycle Frequency ◽  
Mechanical Power Output ◽  
Work Done ◽  
Rest Length

1. The mechanical power output of a synchronous insect muscle was determined by measuring tension as the muscle was subjected to sinusoidal length change and stimuli which occurred at selected phases of the length cycle. The area of the loop formed by plotting muscle tension against length over a full cycle is the work done on that cycle; the work done times the cycle frequency is the mechanical power output. The muscle was a flight muscle of the tettigoniid Neoconocephalus triops. The measurements were made at the normal wing-stroke frequency for flight (25 Hz) and operating temperature (30°C). 2. The power output with a single stimulus per cycle, optimal excursion amplitude, and optimal stimulus phase was 1.52 J kg−1 cycle−1 or 37W kg−1. The maximum power output occurs at a phase such that the onset of the twitch coincides with the onset of the shortening half of the length cycle. The optimum excursion amplitude was 5.5% rest length; with greater excursion, work output declined because of decreasing muscle force associated with the more rapid shortening velocity. 3. Multiple stimulation per cycle increases the power output above that available with twitch contractions. In this muscle, the maximum mechanical power output at 25 Hz was 76 W kg−1 which was achieved with three stimuli per cycle separated by 4-ms intervals and an excursion amplitude of 6.0% rest length. 4. The maximum work output during the shortening of an isotonic twitch contraction was about the same as the work done over a full sinusoidal shortening-lengthening cycle with a single stimulus per cycle and optimum excursion amplitude and phase.

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 1­28 °C, whereas M. sexta muscle contracted at temperatures of 13­42.5 °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 (3­4 lengths s-1 versus 0.6­3.6 lengths s-1 at 13­28 °C), but M. sexta muscle achieved a much higher Vmax at the temperature that this species maintains during flight (10 lengths s-1 at 40­42.5 °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 °C (approximately 100­120 W kg-1). M. sexta muscle achieved instantaneous power outputs of up to 202 W kg-1 at temperatures of 40­42.5 °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 15­30 °C and for M. sexta at temperatures of 30­40 °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.

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.

Shortening deactivation: quantifying a critical component of cyclical muscle contraction

2021 ◽  
Author(s):  
Amy K. Loya ◽  
Sarah K. Van Houten ◽  
Bernadette M. Glasheen ◽  
Douglas M. Swank
Keyword(s):  
Power Output ◽  
Muscle Activation ◽  
Muscle Relaxation ◽  
Length Change ◽  
Isometric Tension ◽  
Energetic Cost ◽  
Muscle Shortening ◽  
Shortening Deactivation ◽  
Muscle Types ◽  
Flight Muscles

A muscle undergoing cyclical contractions requires fast and efficient muscle activation and relaxation to generate high power with relatively low energetic cost. To enhance activation and increase force levels during shortening, some muscle types have evolved stretch activation (SA), a delayed increased in force following rapid muscle lengthening. SA's complementary phenomenon is shortening deactivation (SD), a delayed decrease in force following muscle shortening. SD increases muscle relaxation, which decreases resistance to subsequent muscle lengthening. While it might be just as important to cyclical power output, SD has received less investigation than SA. To enable mechanistic investigations into SD and quantitatively compare it to SA, we developed a protocol to elicit SA and SD from Drosophila and Lethocerus indirect flight muscles (IFM) and Drosophila jump muscle. When normalized to isometric tension, Drosophila IFM exhibited a 118% SD tension decrease, Lethocerus IFM dropped by 97%, and Drosophila jump muscle decreased by 37%. The same order was found for normalized SA tension: Drosophila IFM increased by 233%, Lethocerus IFM by 76%, and Drosophila jump muscle by only 11%. SD occurred slightly earlier than SA, relative to the respective length change, for both IFMs; but SD was exceedingly earlier than SA for jump muscle. Our results suggest SA and SD evolved to enable highly efficient IFM cyclical power generation and may be caused by the same mechanism. However, jump muscle SA and SD mechanisms are likely different, and may have evolved for a role other than to increase the power output of cyclical contractions.

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.

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