The vertical jump is widely used as a field test of performance capability, particularly in games like soccer. Invariably some players perform better than others and, while this is usually put down to greater strength or 'explosive power', there is no detailed information to explain how the muscles around the major joints contribute to this performance and what the nature of this contribution is, or indeed whether aspects of technique are important to performance. Detailed knowledge of this type would be useful to help understand which muscle characteristics are important in successful performance of jumping and may enable insights to be gained in terms of strength training for players. The aim of this study was to investigate the contribution made by the lower limb joints to vertical jump performance by good and poor performers of the counter-movement jump. Two groups of players were selected who were found to be good and poor jumpers, respectively. Each player was required to perform three maximal vertical counter-movement jumps with, and three jumps without, an arm swing. The jump performance was recorded simultaneously by means of a force platform and a ProReflex automatic motion analysis system at 240 Hz. Values at the ankle, knee and hip were computed from these data for joint moments and power.Generally, better jumpers demonstrated greater joint moments, power and work done at the ankle, knee and hip, and as a result jumped higher under both conditions. It appears that the superior performance of the better jumpers was due to greater muscle capability in terms of strength and rate of strength development in all lower limb joints rather than to technique, which differed less noticeably between the groups. It is concluded that the muscle strength characteristics of the lower limb joints are the main determinant of vertical jump performance with technique playing a smaller role.
Assessment of upper limb function, kinematic analysis, and dystonia in patients with spastic diplegia cerebral palsy and periventricular leukomalacia. Seven children with spastic diplegia cerebral palsy and 8 controls underwent upper limb kinematics. Movement duration, average and maximum linear velocity, index of curvature, index of dystonia, and target accuracy and stability were analyzed. In the patients with spastic diplegia, Gross Motor Function and Manual Ability Classification Systems were determined, and spasticity and dystonia were rated using the Modified Ashworth and the Burke-Fahn-Marsden Dystonia scales respectively. Children with spastic diplegia demonstrated a tendency toward higher index of dystonia reflecting overflow, higher index of curvature, lower velocities, and poor target accuracy and stability. All patients showed clinical evidence of dystonia in the upper limbs. Dystonia scores correlated with the Manual Ability Classification System (r = 0.86, P = .01) and with the index of dystonia (r = 0.82, P = .02). Children with spastic diplegia cerebral palsy present dystonia in the upper limbs. This is functionally relevant and can be measured with kinematic analysis.
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