Reliability of the virtual elevation method to evaluate rolling resistance of different mountain bike cross-country tyres

Although a low rolling resistance is advantageous in mountain bike cross-country racing, no studies have used the virtual elevation method to compare tyres from different manufacturers as used in international competitions so far. The aims of this study were to assess the reliability of this method, to compare the off-road rolling resistance between tyres and to calculate the influence on off-road speed.

Nine 29-in. mountain bike cross-country tyres were tested on a course representing typical ground surface conditions 5 or 6 times. The coefficient of rolling resistance was estimated with the virtual elevation method by 3 investigators and corresponding off-road speeds were calculated.

The virtual elevation method was highly reliable (typical error = 0.0006, 2.8%; limits of agreement <0.0005, r ≥ 0.98). The mean coefficient of rolling resistance was 0.0219 and differed from 0.0205 to 0.0237 (P < 0.001) between tyres. The calculated differences in off-road speed amounted to 2.9–3.2% (0% slope) and 2.3–2.4% (10% slope) between the slowest and the fastest tyre.

The reliability of the method and the differences in rolling resistance between the tyres illustrate the value of testing tyres for important competitions on a representative ground surface using the virtual elevation method.     

The association between COMT rs4680 and 5-HTTLPR genotypes and concussion history in South African rugby union players

The objective was to investigate the relationship between Catechol-O-methyltransferase (COMT) rs4680 and serotonin-transporter-linked polymorphic region (5-HTTLPR) genotypes with concussion history and personality traits. Rugby players (“all levels”: n = 303), from high schools (“junior”, n = 137), senior amateur, and professional teams (“senior”, n = 166), completed a self-reported concussion history questionnaire, Cloninger’s Tridimensional Personality Questionnaire, and donated a DNA sample. Participants were allocated into control (non-concussed, n = 140), case (all) (previous suspected or diagnosed concussions, n = 163), or case (diagnosed only) (previous diagnosed concussion, n = 140) groups. COMT rs4680 Val/Val genotypes were over-represented in controls in all levels (P = 0.013, OR:2.00, 95% CI:1.15–3.57) and in juniors (P = 0.003, OR:3.57, 95% CI:1.45–9.09). Junior Val/Val participants displayed increased “anticipatory worry” (P = 0.023). The 5-HTTLPR low expressing group was under-represented in controls when all levels were considered (P = 0.032; OR:2.02, 95% CI:1.05–3.90) and in juniors (P = 0.021; OR:3.36, 95% CI:1.16–9.72). Junior 5-HTTLPR low and intermediate expressing groups displayed decreased “harm avoidance” (P = 0.009), “anticipatory worry” (P = 0.041), and “fear of uncertainty” (P < 0.001). This study provides preliminary indications that personality associated genetic variants can influence concussion in rugby.     

‘Yes we are inclusive’: Examining provision for young people with disabilities in community sport clubs

The last two decades within Australia have witnessed a range of policies and strategies seeking to promote the inclusion of young people with disabilities within mainstream community sport clubs. Whilst research at an institutional level has highlighted the problems with mainstreaming agendas, few studies have examined how grassroots clubs, as key components of the supply side of inclusive provision seek to respond to such policy imperatives. In this paper, therefore, the authors provide a critical analysis of the ways in which clubs engage with inclusion policies in practice. Theoretically, the authors draw on the concept of policy enactment and educational inclusivity. Through analysis of semi-structured interviews with club volunteers, the findings illustrate three key areas. Firstly, the importance of individual volunteers in establishing and developing provision within clubs; secondly, the largely separatist nature of disability provision within clubs; and thirdly, that policies tend to encourage club to focus on narrow forms of participation that lead to competitive pathways and mirror the structure of mainstream sport. In the conclusion, the authors problematize the notion of inclusion presented in policy and practice, suggesting such imperatives do not encourage a holistic approach.     

Differential effects of attentional focus strategies during long-term resistance training

The purpose of this study was to investigate the effects of using an internal versus external focus of attention during resistance training on muscular adaptations. Thirty untrained college-aged men were randomly assigned to an internal focus group (INTERNAL) that focused on contracting the target muscle during training (n?=?15) or an external focus group (EXTERNAL) that focused on the outcome of the lift (n?=?15). Training for both routines consisted of 3 weekly sessions performed on non-consecutive days for 8 weeks. Subjects performed 4 sets of 8–12 repetitions per exercise. Changes in strength were assessed by six repetition maximum in the biceps curl and isometric maximal voluntary contraction in knee extension and elbow flexion. Changes in muscle thickness for the elbow flexors and quadriceps were assessed by ultrasound. Results show significantly greater increases in elbow flexor thickness in INTERNAL versus EXTERNAL (12.4% vs. 6.9%, respectively); similar changes were noted in quadriceps thickness. Isometric elbow flexion strength was greater for INTERNAL while isometric knee extension strength was greater for EXTERNAL, although neither reached statistical significance. The findings lend support to the use of a mind–muscle connection to enhance muscle hypertrophy.     

The effect of altered pitch length on performance and technique in junior fast bowlers

The aim of this study was to assess the effect of pitch length (20.12 m [full length], 18 m and 16 m) on the fast bowling performance and technique of junior cricketers. Performance measures included ball release speed and accuracy, while technique variables evaluated were those shown to be related to the aetiology of lower back injury. Thirty-seven fast bowlers from the under-11 (n=14), under-13 (n=11) and under-15 (n=12) age groups were filmed bowling five deliveries at each of the above pitch lengths. Two synchronized NAC video cameras operating at 200 Hz permitted three-dimensional reconstruction of the hip and shoulder alignments, while a standard digital video camera operating at 50 Hz (positioned perpendicular to the bowling action) was used to measure front knee angle and ball release speed. Accuracy scores were taken from a zoned target at the batsman's stumps. A two-way analysis of variance with repeated measures (with age and pitch length as the between- and within-participant variables, respectively) was used to compare each age group at the 0.05 significance level. Results showed that accuracy improved in all age groups at shorter pitch lengths, although ball velocity remained constant throughout all trials. Shoulder counter-rotation increased significantly for the under-13 bowlers when bowling on the full-length pitch in comparison with the two shorter lengths. Counter-rotation also increased on the full-length pitch in the under-11 age group, although this increase was not significant. The under-15 bowlers' techniques did not change as pitch length increased. As under-11 and under-13 bowlers adopted a "safer" bowling action with superior accuracy on the 18?m compared with the full length pitch, it was concluded that these age groups should bowl on an 18?m pitch to reduce the likelihood of lower back injuries and improve accuracy.     

Application of the LaGrange polynomial in skeletal muscle fatigue analysis

The percentage of decrement in torque and the number of serial contractions are mutually exclusive methodological controls in the study of muscular fatigue. This paper examines the feasibility of using the LaGrange polynomial in the analysis of voluntary muscular fatigue patterns. Twenty-one men (ages 20-60 years) reported to the orthopedic biomechanics laboratory on 2 days separated by 4 months. During both sessions, participants completed three maximal isokinetic (180 deg x s(-1)) contractions of the knee extensors to serve as baseline, before starting the fatigue protocol. The fatigue protocol consisted of serial contractions until a 50% strength decrement was reached. The LaGrange polynomial was first used to interpolate the individual fatigue pattern for each participant into 15 data points (trials). Data analysis was then conducted on these 15 data points. Intraclass correlation analysis of variance showed that the reliability of baseline torque was very good (.93). Baseline torque, the average of three trials, exhibited a 5.4 Nm (6%) increase from the first to second test session (p < .05). The mean level of torque, average of the 15-point fatigue pattern, also increased 7.5 Nm (15%) on the second test session (p < .05). The classic torque deficit for the first trial of a fatigue series was preserved by the interpolation method. Serial contractions resulted in an average decrease in torque of 29.5 Nm (50%) from the first to last trial (p <.05). The interpolation method also retained the linear and quadratic trend components commonly observed for isometric and isokinetic fatigue patterns. The two trend components accounted for 94.7% of the total trial variance. It was concluded that the LaGrange polynomial used to interpolate fatigue patterns to fewer data points was successful.     

Colour-based rigid body tracking using three-dimensional graphics models

This paper introduces the first stage of a new model-based approach to three-dimensional (3D) human movement tracking. A ‘generate-and-test’ matching procedure was adopted by matching rendered images of a 3D computer graphics model of the human body to target images of rigid body motion. The set of pixels to be compared were just those corresponding to the model of the body in the rendered images. The matching criterion to optimize model position and orientation was based on the minimisation of the RGB (red-green-blue) colour difference between generated model images and associated target images. The method was able to track synthetic image sequences of a half twisting somersault accurately with root-mean-square (rms) errors of less than 5 mm and 0.3∘ for position and orientation estimates respectively. The suitability of the proposed approach for rigid body motion tracking was supported by additional tracking experiments on video image sequences of ‘wooden cross’ trajectories. Comparisons of tracked estimates against manual digitizing estimates returned relatively small rms difference values on both side somersault and twisting somersault movements. The proposed approach has the potential to track video images of a human torso using a rigid body model and hence to track articulated movements by successively adding segments to the model in a hierarchical manner.