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Rachel L. Wright, Dan M. Wood and David V.B. James

The aims of the study were to investigate whether starting cadence had an effect on 10-s sprint-performance indices in friction-loaded cycle ergometry and to investigate the influence of method of power determination. In a counterbalanced order, 12 men and 12 women performed three 10-s sprints using a stationary (0 rev/min), moderate (60 rev/min), and high (120 rev/min) starting cadence Calculated performance indices were peak power, cadence at peak power, time to peak power, and work to peak power. When the uncorrected method of power determination was applied, there was a main effect for starting cadence in female participants for peak power (stationary 635 ± 183.7 W, moderate 615.4 ± 168.9 W and high 798.4 ± 120.1 W) and cadence at peak power (89.8 ± 2.3 rev/min, 87.9 ± 21.5 rev/min, and 113.1 ± 12.5 rev/min). For both the uncorrected and directly measured methods of power determination in men and women, there was a main effect for starting cadence for time to peak power and work to peak power. In women, for an uncorrected method of power determination, it can be concluded that starting cadence does affect peak power and cadence at peak power. This effect is, however, negated by a direct-measurement method of power determination. In men and women, for both uncorrected and directly measured methods o power determination, time to peak power and work to peak power were affected by starting cadence. Therefore, a higher-cadence start is unsuitable, particularly when sprint-performance indices are determined from an uncorrected method.

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Matt R. Cross, Farhan Tinwala, Seth Lenetsky, Scott R. Brown, Matt Brughelli, Jean-Benoit Morin and Pierre Samozino

computation of horizontal force in resisted sprinting, and to critically discuss the impact of methodological approach on training applicability. Interplay of Mechanics During Sprinting Acceleration During sprinting acceleration, the force produced by muscle aims to overcome inertia and any friction forces

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Matt R. Cross, Matt Brughelli, Pierre Samozino, Scott R. Brown and Jean-Benoit Morin

Purpose:

To ascertain whether force-velocity-power relationships could be compiled from a battery of sled-resisted overground sprints and to clarify and compare the optimal loading conditions for maximizing power production for different athlete cohorts.

Methods:

Recreational mixed-sport athletes (n = 12) and sprinters (n = 15) performed multiple trials of maximal sprints unloaded and towing a selection of sled masses (20–120% body mass [BM]). Velocity data were collected by sports radar, and kinetics at peak velocity were quantified using friction coefficients and aerodynamic drag. Individual force–velocity and power–velocity relationships were generated using linear and quadratic relationships, respectively. Mechanical and optimal loading variables were subsequently calculated and test–retest reliability assessed.

Results:

Individual force–velocity and power–velocity relationships were accurately fitted with regression models (R 2 > .977, P < .001) and were reliable (ES = 0.05–0.50, ICC = .73–.97, CV = 1.0–5.4%). The normal loading that maximized peak power was 78% ± 6% and 82% ± 8% of BM, representing a resistance of 3.37 and 3.62 N/kg at 4.19 ± 0.19 and 4.90 ± 0.18 m/s (recreational athletes and sprinters, respectively). Optimal force and normal load did not clearly differentiate between cohorts, although sprinters developed greater maximal power (17.2–26.5%, ES = 0.97–2.13, P < .02) at much greater velocities (16.9%, ES = 3.73, P < .001).

Conclusions:

Mechanical relationships can be accurately profiled using common sled-training equipment. Notably, the optimal loading conditions determined in this study (69–96% of BM, dependent on friction conditions) represent much greater resistance than current guidelines (~7–20% of BM). This method has potential value in quantifying individualized training parameters for optimized development of horizontal power.

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Christina Åsan Grasaas, Gertjan Ettema, Ann Magdalen Hegge, Knut Skovereng and Øyvind Sandbakk

This study investigated changes in technique and efficiency after high-intensity exercise to exhaustion in elite cross-country skiers. Twelve elite male skiers completed 4 min submaximal exercise before and after a high-intensity incremental test to exhaustion with the G3 skating technique on a 5% inclined roller-ski treadmill. Kinematics and kinetics were monitored by instrumented roller skis, work rate was calculated as power against roller friction and gravity, aerobic metabolic cost was determined from gas exchange, and blood lactate values indicated the anaerobic contribution. Gross efficiency was the work rate divided by aerobic metabolic rate. A recovery period of 10 min between the incremental test and the posttest was included to allow the metabolic values to return to baseline. Changes in neuromuscular fatigue in upper and lower limbs before and after the incremental test were indicated by peak power in concentric bench press and squat-jump height. From pretest to posttest, cycle length decreased and cycle rate increased by approximately 5% (P < 0.001), whereas the amount of ski forces did not change significantly. Oxygen uptake increased by 4%, and gross efficiency decreased from 15.5% ± 0.7% to 15.2% ± 0.5% from pretest to posttest (both P < .02). Correspondingly, blood lactate concentration increased from 2.4 ± 1.0 to 6.2 ± 2.5 mmol/L (P < .001). Bench-press and squat-jump performance remained unaltered. Elite cross-country skiers demonstrated a less efficient technique and shorter cycle length during submaximal roller-ski skating after high-intensity exercise. However, there were no changes in ski forces or peak power in the upper and lower limbs that could explain these differences.

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Dionne A. Noordhof, Carl Foster, Marco J.M. Hoozemans and Jos J. de Koning

Speed skating posture, or technique, is characterized by the push-off angle or effectiveness (e), determined as the angle between the push-off leg and the ice; the preextension knee angle (θ 0); and the trunk angle (θ 1). Together with muscle-power output and environmental conditions, skating posture, or technique, determines velocity (v).

Purpose:

To gain insight into technical variables that are important to skate efficiently and perform well, e, θ 0, θ 1, and skating v were determined every lap during a 5000-m World Cup. Second, the authors evaluated if changes (Δ) in e, θ 0, and θ 1 are associated with Δv.

Methods:

One camera filmed the skaters from a frontal view, from which e was determined. Another camera filmed the skaters from a sagittal view, from which θ 0 and θ 1 were determined. Radio-frequency identification tags around the ankles of the skaters measured v.

Results:

During the race, e progressively increased and v progressively decreased, while θ 0 and θ 1 showed a less consistent pattern of change. Generalized estimating equations showed that Δe is significantly associated with Δv over the midsection of the race (β = −0.10, P < .001) and that Δθ 0 and Δθ 1 are not significantly associated with Δv.

Conclusions:

The decrease in skating v over the race is not due to increases in power losses to air friction, as knee and trunk angle were not significantly associated with changes in velocity. The decrease in velocity can be partly ascribed to the decrease in effectiveness, which reflects a decrease in power production associated with fatigue.

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Andrea Monte, Francesca Nardello and Paola Zamparo

Purpose:

The effects of different loads on kinematic and kinetic variables during sled towing were investigated with the aim to identify the optimal overload for this specific sprint training.

Methods:

Thirteen male sprinters (100-m personal best: 10.91 ± 0.14 s) performed 5 maximal trials over a 20-m distance in the following conditions: unloaded and with loads from 15% to 40% of the athlete’s body mass (BM). In these calculations the sled mass and friction were taken into account. Contact and flight times, stride length, horizontal hip velocity (vh), and relative angles of hip, knee, and ankle (at touchdown and takeoff) were measured step by step. In addition, the horizontal force (Fh) and power (Ph) and maximal force (Fh0) and power (Ph0) were calculated.

Results:

vh, flight time, and step length decreased while contact time increased with increasing load (P < .001). These variables changed significantly also as a function of the step number (P < .01), except between the 2 last steps. No differences were observed in Fh among loads, but Fh was larger in sled towing than in unloaded. Ph was unaffected by load up to +20%BM but decreased with larger loads. Fh0 and Ph0 were achieved at 20%BM. Up to 20%BM, no significant effects on joint angles were observed at touchdown and takeoff, while at loads >30%BM joint angles tended to decrease.

Conclusion:

The 20%BM condition represents the optimal overload for peak power production—at this load sprinters reach their highest power without significant changes in their running technique (eg, joint angles).

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. Martin * Christopher J. Davidson * Eric R. Pardyjak * 3 2007 2 1 5 21 10.1123/ijspp.2.1.5 Original Investigations Effect of Starting Cadence on Sprint-Performance Indices in Friction-Loaded Cycle Ergometry Rachel L. Wright * Dan M. Wood * David V.B. James * 3 2007 2 1 22 33 10.1123/ijspp.2

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Pål Haugnes, Jan Kocbach, Harri Luchsinger, Gertjan Ettema and Øyvind Sandbakk

variations in opposing forces from snow-ski friction, air drag, and gravity across different terrains. By contrast, work rate and the fractional utilization of WR max provide a more universal understanding on how skiers distribute power during training and competition. Concurrent information on external

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Abderrahmane Rahmani, Pierre Samozino, Jean-Benoit Morin and Baptiste Morel

¯ = ( m ul + m b ) · a b + ( m ul + m b ) · g + F f (1) where m ul  = upper-limb mass estimated as a fraction of body mass from Winter’s table 22 (10% of body mass for the 2 upper limbs), m b  = lifted mass, and F f  = the friction force of the guided system determined during a freefall test. F ¯ and

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Amador García-Ramos and Slobodan Jaric

avoid wrong conclusions about the reliability of fitness tests by incrementing the statistical power. Finally, it should be noted that to simplify the testing procedure, the friction force of the Smith machine barbell was not added for force computations. Therefore, although the magnitude of the F