ACE ID genotype and leg power in Rugby Union players.

AIM: The present study examined the hypothesis that there were no significant differences between forwards and backs in the elements of leg power between the ID and DD genotypes of the ACE (I/D) gene in developing young adult Rugby Union players. METHODS: Sixty-eight players were recruited to identify the distribution of genotypes between forwards and backs. Fifty-eight players were investigated for leg power. Forwards (n=28) comprised 15 ID and 13 DD genotypes, and backs (n=30) 19 ID and 11 DD genotypes. Leg power was measured on a force platform using a counter movement jump; the parameters of interest were peak and relative force, peak and relative power, displacement and velocity. The three-primer polymerase chain reaction was used to assay the region of interest for I and D variants of the ACE gene. The distribution of genotypes was determined by chi-square and comparisons between forwards and backs made using the independent t-test. RESULTS: No significant differences were identified in the distribution of genotypes between forwards and backs (χ2=2.2, P=0.336). However, significant differences were identified between forwards and backs in a number of components of leg power. Backs had significantly larger values than forwards for relative force (1.50 vs. 1.30 Wt%, P=0.001) and relative power (27.1 vs. 24.3 W.kg-1, P=0.034) for the ID genotype, whereas backs had significantly larger values than forwards for displacement (0.42 vs. 0.38 m, P=0.049) and velocity (2.76 vs. 2.55 m.s.(-1), P=0.007) for the DD genotype. CONCLUSION: The characteristics of leg power identified will enhance the functional requirements of players according to playing position and commitment.

"Essential noise" - enhancing variability of informational constraints benefits movement control: a comment on Waddington and Adams (2003).

This commentary proposes a dynamical systems perspective to re-interpret data from a group of international soccer players demonstrating that wearing textured insoles in soccer boots enhanced tactile information from the sole of the foot and increased movement discrimination capacity in ankle inversion sensitivity tests to levels similar to those in barefoot conditions. Theoretical arguments on the functional role of variability induced in the sensorimotor system by textured insoles, acting as a form of "essential noise" to enhance the accuracy of foot positioning are presented. It seems that, far from interfering with motor performance, variability can actually enhance perception of information to support motor performance. The addition of intermittent, intermediate levels of noise in a perceptual motor context may benefit performers by helping them to pick up information signals from background structure. Movement system variability is conceived as noise induced resonance benefiting the pick up of information to regulate behaviour. Variability can be functional in practical programmes to offset negative effects of losses in sensory sensitivity through ageing, disease, illness, or injury.

Anthropometric and kinematic influences on release speed in men's fast-medium bowling.

The main aim of this study was to identify significant relationships between selected anthropometric and kinematic variables and ball release speed. Nine collegiate fast-medium bowlers (mean +/- s: age 21.0 +/- 0.9 years, body mass 77.2 +/- 8.1 kg, height 1.83 +/- 0.1 m) were filmed and reconstructed three-dimensionally. Ball release speeds were measured by a previously validated Speedchek Personal Sports Radar (Tribar Industries, Canada). Relationships between selected anthropometric variables and ball release speed and between kinematic variables and ball release speed were investigated using Pearson's product-moment correlation coefficients (r). A significant relationship was found between the horizontal velocity during the pre-delivery stride (r = 0.728, P < 0.05) and ball release speed (31.5 +/- 1.9 m(-1) s(-1)). We believe that the high correlation was due to the bowlers using techniques that allowed them to contribute more of the horizontal velocity created during the run-up to ball release speed. We also found that the angular velocity (40.6 +/- 3.4 rad x s(-1)) of the right humerus had a low correlation (r = 0.358, P > 0.05) with ball release speed. Although the action of the wrist was not analysed because of an inadequate frame rate, we found high correlations between ball release speed and shoulder-wrist length (661 +/- 31 mm; r = 0.626, P < 0.05) and ball release speed and total arm length (860 +/- 36 mm; r = 0.583, P < 0.05). We conclude that the variance in release speed within this group may be accounted for by the difference in radial length between the axis of rotation at the glenohumeral joint and the release point.