Search Results

You are looking at 11 - 20 of 300 items for :

  • "force platform" x
Clear All
Restricted access

Brad Hodgson, Laurie Tis, Steven Cobb and Elizabeth Higbie

Objective:

To examine the effects of external ankle support on vertical ground-reaction forces (VGRF) and kinematic data.

Methods:

Subjects completed 2 braced and 2 nonbraced 0.61-m hanging drop landings onto a force platform. Kinematic data were collected with 8 digital-optical cameras sampling at 120 Hz.

Subjects:

12 Division I female volleyball players.

Statistical Analysis:

A repeated-measures ANOVA with Bonferroni correction (P < .05) was used to determine whether significant differences existed between test conditions for peak VGRF, loading rate, hip angle, knee angle, and ankle angle at right-foot contact for peak 1 and peak 2 of the VGRF curve over the first 100 milliseconds of the landing phase, as well as total hip range of motion (ROM), total knee ROM, and total ankle ROM for the entire landing phase.

Results:

There were significant increases in peak P1 and LR1 and a significant decrease in ankle-angle change at right-foot contact in braced trials compared with the nonbraced condition.

Restricted access

Liam P. Kilduff, Huw Bevan, Nick Owen, Mike I.C. Kingsley, Paul Bunce, Mark Bennett and Dan Cunningham

Purpose:

The ability to develop high levels of muscle power is considered an essential component of success in many sporting activities; however, the optimal load for the development of peak power during training remains controversial. The aim of the present study was to determine the optimal load required to observe peak power output (PPO) during the hang power clean in professional rugby players.

Methods:

Twelve professional rugby players performed hang power cleans on a portable force platform at loads of 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their predetermined 1-repetition maximum (1-RM) in a randomized and balanced order.

Results:

Relative load had a significant effect on power output, with peak values being obtained at 80% of the subjects’ 1-RM (4466 ± 477 W; P < .001). There was no significant difference, however, between the power outputs at 50%, 60%, 70%, or 90% 1-RM compared with 80% 1-RM. Peak force was produced at 90% 1-RM with relative load having a significant effect on this variable; however, relative load had no effect on peak rate of force development or velocity during the hang power clean.

Conclusions:

The authors conclude that relative load has a significant effect on PPO during the hang power clean: Although PPO was obtained at 80% 1-RM, there was no significant difference between the loads ranging from 40% to 90% 1-RM. Individual determination of the optimal load for PPO is necessary in order to enhance individual training effects.

Restricted access

Aaron T. Scanlan, Jordan L. Fox, Nattai R. Borges and Vincent J. Dalbo

Purpose:

Declines in high-intensity activity during game play (in-game approach) and performance tests measured pre- and postgame (across-game approach) have been used to assess player fatigue in basketball. However, a direct comparison of these approaches is not available. Consequently, this study examined the commonality between in- and across-game jump fatigue during simulated basketball game play.

Methods:

Australian, state-level, junior male basketball players (n = 10; 16.6 ± 1.1 y, 182.4 ± 4.3 cm, 68.3 ± 10.2 kg) completed 4 × 10-min standardized quarters of simulated basketball game play. In-game jump height during game play was measured using video analysis, while across-game jump height was determined pre-, mid-, and postgame play using an in-ground force platform. Jump height was determined using the flight-time method, with jump decrement calculated for each approach across the first half, second half, and entire game.

Results:

A greater jump decrement was apparent for the in-game approach than for the across-game approach in the first half (37.1% ± 11.6% vs 1.7% ± 6.2%; P = .005; d = 3.81, large), while nonsignificant, large differences were evident between approaches in the second half (d = 1.14) and entire game (d = 1.83). Nonsignificant associations were evident between in-game and across-game jump decrement, with shared variances of 3–26%.

Conclusions:

Large differences and a low commonality were observed between in- and across-game jump fatigue during basketball game play, suggesting that these approaches measure different constructs. Based on our findings, it is not recommended that basketball coaches use these approaches interchangeably to monitor player fatigue across the season.

Restricted access

Kim Bennell, Kay Crossley, Tim Wrigley and Julie Nitschke

The aim of our study was to assess the interday test-retest reliability (focussing on the separate contribution of systematic and random error) of selected 10-trial mean ground reaction force (GRF) parameters and GRF symmetry indices measured during running. Ten competitive male heel-strike runners (aged, 26.2 ± 5.7 years) performed 10 successful running trials across the force platform at a constant velocity of 4.0 m · s-1 ±10% wearing their customary running footwear. The testing procedure was repeated under similar conditions 1 week later. The results showed no statistically significant differences between the means of Test 1 and Test 2 for most GRF parameters and symmetry indices, indicating non-significant systematic error. Correlation coefficients ranged from 0.73 to 0.99 for GRF parameters. Random error was small with SEmeas less than 10% of the Test 1 mean value for almost all GRF parameters. Symmetry indices displayed correlation coefficients ranging from −0.44 to 0.91. Based on these and the size of the SEmeas, the symmetry indices displayed variable reliability, with the most reliable being those associated with peak vertical active force and peak horizontal propulsive force.

Restricted access

Rodolfo B. Parreira, Marcela C. Boer, Lucas Rabello, Viviane de Souza P. Costa, Eros de Oliveira Jr. and Rubens A. da Silva

The aim of this study was to evaluate the changes in center of pressure (COP) movement in four time intervals (5, 10, 15 and 30 s) during a one-leg stance test performed by young and elderly adults. Twelve young adults (mean 20 years) and 12 elderly subjects (mean 68 years) participated in this study. The subjects performed three 30 s trials of an eyes open one-leg stance test on a force platform, in which the COP parameter was computed at four points in time from same original COP signal. Significant differences were found between the young and elderly adults (P < .007) only at the 10, 15 and 30 s intervals. For both groups, COP changes were significantly different between the 5 s time interval and other intervals (10, 15 and 30 s). In conclusion, these results pointed out that age-related difference in COP changes were time dependent. This suggests that the use of longer durations increases the possibility of distinguishing more subtle differences in postural strategy among different groups of subjects.

Restricted access

Nick Dobbin, Richard Hunwicks, Ben Jones, Kevin Till, Jamie Highton and Craig Twist

force platform with an immovable bar positioned to correspond with the second-pull clean position, just below the crease of the hip. 14 Participants are then instructed to pull as fast and hard as possible, enabling various kinetic measures to be quantified from ground-reaction forces. 15 , 16 With

Restricted access

Stefan Sebastian Tomescu, Ryan Bakker, Tyson A.C. Beach and Naveen Chandrashekar

Musculoskeletal simulations of high-impact movements are being increasingly utilized to gain insight into body dynamics, injury mechanisms, and tissue loading. 1 – 3 Conducting these simulations involves collecting body marker and force platform data, calculating joint moments, and computing

Restricted access

Andrew G Jameson, Stephen J Kinzey and Jeffrey S Hallam

Context:

Cryotherapy is commonly used in the care of acute and chronic injuries. It decreases pain, reduces swelling, and causes vasoconstriction of blood vessels. Its detrimental effects on motor activity might predispose physically active individuals to further injury.

Objective:

To examine the effects of cryotherapy on vertical-ground-reaction-force (VGRF) during a 2-legged landing from a 2-legged targeted vertical jump.

Design:

2 × 4 MANOVA with repeated measures.

Setting:

Biomechanics laboratory.

Participants:

10 men, means: 22.40 ± 1.26 years, 76.01 ± 26.95 kg, 182.88 ± 6.88 cm.

Intervention:

VGRF during landing from a targeted vertical jump (90% of maximum) was measured before and after four 20-minute cryotherapy treatments.

Results:

There were no significant differences in VGRF as a result of cryotherapy.

Conclusion:

Under the constraints of this study there is no evidence that returning to activity immediately after cryotherapy predisposes an athlete to injury because of a change in VGRF.

Restricted access

Mary E. Naylor and William A. Romani

Context:

There is a growing need for objective measures of proprioception and balance in athletic females.

Objective:

To determine the intertester and intratester reliability of the Neurocom Balance Master (NBM) forward lunge (FL), step up and over (SUO), and step quick turn (SQT) tests on a young, healthy, female population.

Design:

Repeated measures design.

Setting:

University medical laboratory.

Participants:

15 young healthy female volunteers (height 155.1 cm ± 18.5 cm, mass 61.1 kg ± 7.3 kg, age 24.2 years ± 2.9 years).

Measurements:

The average of three trials on the FL, SUO, and SQT taken during each of three testing sessions on the NBM long force plate.

Results:

Inter and intratester reliability for the FL (ICC r = 0.71 to r = 0.93) and SQT (ICC r = 0.70 to r = 0.88) ranged from good to excellent while reliability for the SUO ranged from fair to excellent (ICC r = 0.59 to r = 0.92).

Conclusions:

The three NBM tests are reliable in healthy, young, physically active females.

Restricted access

Yusuke Ikeda, Hiroshi Ichikawa, Rio Nara, Yasuhiro Baba, Yoshimitsu Shimoyama and Yasuyuki Kubo

This study investigated factors that determine the velocity of the center of mass (CM) and flight distance from a track start to devise effective technical and physical training methods. Nine male and 5 female competitive swimmers participated in this study. Kinematics and ground reaction forces of the front and back legs were recorded using a video camera and force plates. The track start was modeled as an inverted pendulum system including a compliant leg, connecting the CM and front edge of the starting block. The increase in the horizontal velocity of the CM immediately after the start signal was closely correlated with the rotational component of the inverted pendulum. This rotational component at hands-off was significantly correlated with the average vertical force of the back plate from the start signal to hands-off (r = .967, P < .001). The flight distance / height was significantly correlated with the average vertical force of the front plate from the back foot-off to front foot-off (r = .783, P < .01). The results indicate that the legs on the starting block in the track start play a different role in the behavior of the inverted pendulum.