Cesar Meylan

Date of Award

2009

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Master of Science (Sports Science)

School

School of Exercise, Biomedical and Health Sciences

First Supervisor

Professor John Cronin

Second Supervisor

Associate Professor Ken Nosaka

Abstract

The purpose of this thesis was to provide an in depth analysis of the kinematics and kinetics associated with unilateral vertical (VCMJ), horizontal (HCMJ) and lateral (LCMJ) countermovement jump performance. This thesis consists of i) two reviews of literature discussing the isoinertial assessment of eccentric force capability and acyclic jump assessment with the intention of providing recommendations for future research design and measurement of lower limb muscular capability; ii) a technical note determining the appropriate start threshold (2.5, 5 and 10% of bodyweight- BW) for the force-time curve analysis of the three different unilateral jumps; iii) a research note investigating the variability and influence of eccentric kinematics thought important determinants of VCMJ, HCMJ and LCMJ performance; and iv) an experimental study establishing the reliability of a variety of kinetic and temporal variables for the VCMJ, HCMJ and LCMJ, comparing the kinetic differences across the three jumps, examining the leg asymmetry between the dominant and non dominant legs in the variables of interest, and determining the best predictors of each jump performance.

In terms of the experimental papers, the aim of the technical note was to determine the appropriate start threshold for analysis of a force-time curve. Ten state league soccer players (age 21.0 ± 3.1 years, height 178.6 ± 6.5 cm, mass 75.4 ± 5.0 kg) performed three trials of a bilateral countermovement jump. Significant differences (p < 0.05) were found in all variables except eccentric and concentric peak force and force at zero velocity between 2.5% and 10% and 5% and 10% thresholds. Similar results were found for the 2.5% and 5% threshold variables except that no significant difference was found in the concentric ground contact time. The different thresholds did not appear to have any influence on the variability of the measurement and only concentric time to peak force was found to have high variability (coefficient of variation - CV= 51.7-55.5%). It was concluded that any of the start thresholds (2.5, 5.0 and 10% BW) could be used to determine the starting point of a CMJ considering their reliability; however, the 2.5% BW threshold was preferable as most of the force-time signal could be considered for analysis and differences in eccentric and concentric kinematic and kinetic variables where found when a higher threshold was used.

For the research note, thirty team sport athletes (age 21.9 ± 3.8 years, height 1.77 ± 0.06 m, body mass 75.5 ± 9.0 kg) performed three trials of a unilateral VCMJ, HCMJ and LCMJ on both legs. It was observed that the variability (CV) of the eccentric variables (i.e. peak velocity, peak displacement, ground contact time) was the lowest for the VCMJ (CV = 8.5-10.6%), and the highest for the HCMJ (CV = 11.7-13.5%). The eccentric ground contact time was significantly (p < 0.05) longer (-0.18 s) for the HCMJ and LCMJ compared to the VCMJ. The amplitude of the eccentric displacement was significantly (p < 0.05) greater (3-5 cm) in the LCMJ compared to the other two jumps and eccentric displacement of the HCMJ was also significantly (p < 0.05) greater (2 cm) compared to the VCMJ. The peak eccentric velocity was significantly faster (0.06 to 0.15 m.s-1 ) for the VCMJ compared to the other jumps and the LCMJ eccentric peak velocity was also significantly (p < 0.05) faster (0.09 m.s-1 ) than that of the HCMJ. It seems that in the absence of instruction and standardization of the countermovement, eccentric phase kinematics remains relatively stable over trials and between legs. In terms of the between jump analysis, it seems that the eccentric phase kinematics are relatively unique to each jump type.

The experimental study used the same thirty subjects as the research note. They performed, on two separate occasions, three trials of unilateral VCMJ, HCMJ and LCMJ on each leg. It was found that from the eighteen variables studied, eccentric and concentric peak force and concentric peak power were the only variables with acceptable reliability as determined by previously published criteria (CV= 3.3-15.1 %; ICC= 0.70-0.96). Comparisons of eccentric and concentric peak vertical ground reaction force (VGRF) and concentric peak power among the three jumps revealed that these three variables were significantly (p < 0.01) greater in the VCMJ compared to the HCMJ and LCMJ (eccentric peak force: 14-16%; concentric peak power: 45-51 %), but no significant differences were found between the HCMJ and LCMJ. No significant leg asymmetries were found between the dominant and non dominant leg in any kinetic variables but significant differences (p < 0.01) were found in the actual jump height or distance. The asymmetry index between limbs ranged from -2.1 % to 9.3% for all variables. Concentric peak vertical power output was found to be the best single predictor of VCMJ perfo1mance Gump height) accounting for 79% of the shared variance between the two variables. The addition of concentric peak VGRF and eccentric peak VGRF to the statistical model improved the common variance associated with vertical jump to 95.9%. The best predictor model for HCMJ performance (distance jumped) included only one variable, horizontal concentric peak power which accounted for a shared variance of 42.6% with horizontal jump distance. Eccentric peak VGRF was the only variable entered into the predictor model of LCMJ performance (i.e. distance jumped) and accounted for only 14.9% of that performance. It was concluded that eccentric and concentric peak force and concentric peak power can be used confidently as measures of functional strength and power. The differences found in VGRF and vertical power between the VCMJ and HCMJ or LCMJ, confirmed that the vertical force and power requirements between multidirectional unilateral jump movements are different. Differences between the dominant and non-dominant leg are likely to be found in a healthy athletic population the magnitude of this asymmetry differing depending on the direction of force application. However, it is advised that these differences should fall within a 10 to 15% range in order to reduce potential injury risk and optimize performance. Finally, developing and monitoring changes in horizontal and vertical concentric leg power seem appropriate for improving HCMJ and VCMJ performance respectively. As different strength and power characteristics were associated with different jump performances depending on the movement direction, leg power assessment needs to include assessment in all three directions and/or match sport or activity specific needs. It is fundamental to keep such information in mind when the goals of a training program are being set and monitoring of progress is undertaken.

LCSH Subject Headings

Edith Cowan University. Faculty of Computing, Health and Science -- Dissertations
Jumping
Kinesiology
Muscles -- Physiology
Leg -- Physiology
Human mechanics

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