Search Results

You are looking at 1 - 10 of 2,081 items for :

  • Sport and Exercise Science/Kinesiology x
Clear All
Restricted access

Andrea Biscarini

The author derived the exact analytical expression of the instantaneous joint power in exercises with single-joint, variable-resistance, selectorized strength-training equipment, taking into account all the relevant geometric, kinematic, and dynamic variables of both the movable equipment elements (resistance input lever, cam–pulley system, weight stack) and of the user’s exercising limb. A numerical algorithm was also designed to express, in the presence of a cam, the rectilinear kinematic variables of the weight stack as a function of the rotational kinematic variables of the resistance input lever, and vice versa. Given that information, one can measure the value of the instantaneous and mean joint power exclusively by means of a linear encoder placed on the weight stack or, alternatively, only by the use of an angular encoder placed on the rotational axis of the resistance lever. The results highlight that, for knee extension exercises with leg extension equipment, the real values of both instantaneous and mean joint power may differ by more than 50% in comparison with the values obtained by taking into account only the mass and velocity of the weight stack. These differences are notable not only in explosive exercises, but also whenever considerable joint velocities/accelerations occur within the range of motion.

Restricted access

Assane E.S. Niang and Bradford J. McFadyen

The present study investigated the adaptations of specific power bursts during the combined contexts of the proximity (lead vs. trail limb) and height of an obstruction in relation to limb elevation versus progression. Ten young, adult, male subjects walked at their natural speed during unobstructed walking and the bilateral avoidance of moderate and high obstacles. Hip flexor generation power was unaffected by obstacle height for the leading limb and always delayed for the trailing limb. The knee extensor absorption power burst at toe-off was also eliminated for the trailing limb and was found to reappear in mid-swing. Few differences were seen for ankle push-off power. The results suggest that the hip joint is dedicated to limb advancement only, while the knee joint is directly involved in limb elevation and the control of multiarticular effects.

Restricted access

Nuria Garatachea, Zoraida Verde, Alejandro Santos-Lozano, Thomas Yvert, Gabriel Rodriguez-Romo, Francisco J. Sarasa, Sonsoles Hernández-Sánchez, Catalina Santiago and Alejandro Lucia

Purpose:

To determine the association of the ACTN3 R577X polymorphism with leg-muscle explosive power in Spanish (white) elite basketball players and controls.

Participants:

100 (60 men) elite basketball players (cases) and 283 nonathletic controls.

Methods:

The authors assessed power performance by means of the vertical-squat and countermovement-jump tests.

Results:

Genotype distributions did not differ between groups (cases: 37.0% [RR], 42.0% [RX], and 21.0% [XX]; controls: 31.8% [RR], 49.8% [RX], and 18.4% [XX]; P = .353). The authors did not observe any effect of the ACTN3 R577X polymorphism on study phenotypes in either group, including when they performed the analyses separately in men and women. They found no association between the ACTN3 R577X polymorphism and the likelihood of being an elite basketball player using the dominant or the recessive model, and the results remained unaltered when the analyses were adjusted for sex, weight, height, and age or when performed for men and women separately.

Conclusions:

Although the ACTN3 R577X is associated with explosive muscle performance and this phenotype is important in the sport of basketball (ie, during jumps), the authors found no association with leg explosive power in elite basket players or with the status of being this type of athlete.

Restricted access

Thomas Haugen, Gøran Paulsen, Stephen Seiler and Øyvind Sandbakk

external power output underlie successful performance in sports. Accordingly, regular assessment of aerobic and anaerobic power informs the overall training strategy of most of today’s elite athletes. Numerous groups have reported contemporary power data from elite athletes, particularly runners, cyclists

Restricted access

Jason D. Stone, Adam C. King, Shiho Goto, John D. Mata, Joseph Hannon, James C. Garrison, James Bothwell, Andrew R. Jagim, Margaret T. Jones and Jonathan M. Oliver

), elicits a near linear decline in barbell velocity, and thus power output. 3 – 5 Recognizing that force and velocity are both required to maintain a given work capacity, muscular fatigue has been defined as the inability to maintain the required or expected power output. 6 Attenuated power production is

Restricted access

Hermann Zbinden-Foncea, Isabel Rada, Jesus Gomez, Marco Kokaly, Trent Stellingwerff, Louise Deldicque and Luis Peñailillo

exertion, which suggests that caffeine ameliorates the discomfort produced by fatigue and enhances motor-unit recruitment. 13 When a high power output is required and during repeated-sprint events, the ergogenic effects are less consistent 12 ; several explanations may be put forward, such as variability

Restricted access

Emma K. Zadow, Cecilia M. Kitic, Sam S.X. Wu and James W. Fell

Advancements in the technology of cycling ergometers have been shown to provide increasing accuracy in the measurement of power output. The measurement of power is an important determinant of performance and is vital for evaluating individual differences in performances, monitoring the

Restricted access

Seiichiro Takei, Kuniaki Hirayama and Junichi Okada

Olympic weight-lifting exercises are among the most powerful movements in sport and are often used by athletes for power enhancement along with other primary power exercises like plyometrics and jump squats. 1 Among weight-lifting exercises, the hang power clean (HPC) is a widely used exercise in

Restricted access

Jonathon Weakley, Carlos Ramirez-Lopez, Shaun McLaren, Nick Dalton-Barron, Dan Weaving, Ben Jones, Kevin Till and Harry Banyard

%) have been demonstrated to promote greater hypertrophic adaptations due to the increased training volume that can be achieved prior to set termination. 4 Alternatively, smaller thresholds (eg, 10% vs 30%) encourage greater development of strength and power due to reduced neuromuscular fatigue and

Restricted access

Jake Schuster, Dan Howells, Julien Robineau, Anthony Couderc, Alex Natera, Nick Lumley, Tim J. Gabbett and Nick Winkelman

allow for effective development and application of running skills and capacities, strength and power, injury prevention, aerobic and anaerobic conditioning, and tactical/technical components. The primary responsibility of physical-preparation programs is to ensure that players spend as much time as