BILATERAL DIFFERENCES IN STEP CHARACTERISTICS WHEN SPRINTING ON THE STRAIGHT AND BANKED BEND OF AN INDOOR 200 M TRACK

Sprinting around a bend is thought to be limited by an athlete’s ability to create force. Bilateral differences in technique in athletes sprinting on an indoor banked 200 m track are not yet fully understood. Four experienced male 400 m runners were studied during sprints on the straight and at the bend apex of lanes one and four. Step time, length, frequency and velocity were calculated using an automatic tracking system operating at 200 Hz. Group mean values were calculated for each contact limb and lane condition. Velocity on the bend compared to the straight decreased in steps from the left (inside) leg to a markedly greater extent (approx. 5%) than in steps from the right (outside) leg (approx. 1%). This may be linked to previously reported differences in force production capacity between inside and outside legs during maximal bend running

Theoretical and methodological aspect of the problem of development and support for talented pre-schoolers

В статье представлен анализ ведущих отечественных и зарубежных исследований в области развития и поддержки одаренных детей дошкольного возраста

A LONGITUDINAL CASE STUDY OF STEP CHARACTERISTICS IN A WORLD CLASS SPRINT ATHLETE

The relative importance of step length (SL) and step frequency (SF) to maximum velocity sprinting is not yet fully understood. One elite male sprinter was studied during five months of training. Step velocity, SL and SF were calculated from 50 Hz video, using manual digitization and 2D DLT, for a total of 113 steps taken from the maximum velocity phase of training sprints. Mean values were calculated for each session and tracked against training diary information gathered from the athlete's coach. Chronological information showed that as the athlete’s training progressed, a link between velocity and SF was maintained whilst mean session SL remained relatively unchanged throughout. For the athlete studied, changes in step velocity as a result of training were shown to occur as a consequence of changes mainly in SF

CHANGES IN STEP CHARACTERISTICS BETWEEN THE MAXIMUM VELOCITY AND DECELERATION PHASES OF THE 100 METRE SPRINT RUN

In a 100 m sprint race, athletes are unable to maintain their maximum velocity through the finish line. The aim of this study was to investigate the contributions of step length and step frequency to changes in velocity as athletes decelerate. Nine well-trained sprint athletes each performed between three and five maximal 100 m sprints. Velocity, step length and step frequency were measured for individual steps in the maximum velocity (30-40 m) and deceleration (70-80 m) phases. On a group level, velocity and step frequency reduced between the maximum velocity and deceleration phases (p < 0.05), whereas step length did not. Individual athlete analyses revealed that the fastest sprinters tended to maintain velocity in the deceleration phase by combining a significant reduction in step frequency with a significant increase in step length

Characterising initial sprint acceleration strategies using a whole-body kinematics approach.

Sprint acceleration is an important motor skill in team sports, thus consideration of techniques adopted during the initial steps of acceleration is of interest. Different technique strategies can be adopted due to multiple interacting components, but the reasons for, and performance implications of, these differences are unclear. 29 professional rugby union backs completed three maximal 30 m sprints, from which spatiotemporal variables and linear and angular kinematics during the first four steps were obtained. Leg strength qualities were also obtained from a series of strength tests for 25 participants, and 13 participants completed the sprint protocol on four separate occasions to assess the reliability of the observed technique strategies. Using hierarchical agglomerative cluster analysis, four clear participant groups were identified according to their normalised spatiotemporal variables. Whilst significant differences in several lower limb sprint kinematic and strength qualities existed between groups, there were no significant between-group differences in acceleration performance, suggesting inter-athlete technique degeneracy in the context of performance. As the intra-individual whole-body kinematic strategies were stable (mean CV = 1.9% to 6.7%), the novel approach developed and applied in this study provides an effective solution for monitoring changes in acceleration technique strategies in response to technical or physical interventions

Enhancing the Initial Acceleration Performance of Elite Rugby Backs. Part II: Insights From Multiple Longitudinal Individual-Specific Case-Study Interventions

Purpose: This study implemented 18-week individual-specific sprint acceleration training interventions in elite male rugby backs based on their pre-determined individual technical needs, and evaluated the effectiveness of these interventions. Methods: Individual-specific interventions were prescribed to five elite rugby backs over an 18-week period. Interventions were informed by the relationships between individual technique strategies and initial acceleration performance, and their strength-based capabilities. Individual-specific changes in technique and initial acceleration performance were measured at multiple time points across the intervention period, and compared to three control participants who underwent their normal sprint training. Results: Of the technique variables intentionally targeted during the intervention period, moderate to very large (ǀdǀ = 0.93 to 3.99) meaningful changes were observed in the participants who received an individual-specific intervention, but not in three control participants. Resultant changes to the intervention participants’ whole-body kinematic strategies were broadly consistent with the intended changes. Moderate to very large (ǀdǀ = 1.11 to 2.82) improvements in initial acceleration performance were observed in participants receiving individual-specific technical interventions, but not in the control participants or the participant who received an individual-specific strength intervention. Conclusions: Individual-specific technical interventions were more effective in manipulating aspects of acceleration technique and performance, compared with the traditional ‘one-size-fits-all’ approach adopted by the control participants. This study provides a novel, evidence-based approach for applied practitioners working to individualize sprint-based practices to enhance acceleration performance

CHANGES IN STEP CHARACTERISTICS DURING SPRINT PERFORMANCE DEVELOPMENT

Horizontal sprint velocity is the product of step length (SL) and step frequency (SF), but the relative importance of these step characteristics (SC) to step velocity (SV) remains uncertain. This study monitored changes in SC for three developing athletes over a 5 week training period. SV, SL and SF were calculated from manually digitized, reconstructed (2D-DLT) 50 Hz video co-ordinates of foot contacts in 60 m sprints. Performance (60 m time) and SV improved where each athlete increased the SC that had correlated significantly (p < 0.05) with SV at the start of training. This suggested that developing athletes initially favoured the SC upon which they relied at the start of training. These findings inform sprint coaching and direct further research into biomechanical variables determining SC and their inter-relationships

Enhancing the Initial Acceleration Performance of Elite Rugby Backs. Part I: Determining Individual Technical Needs

Purpose: This study sought to quantify the within-individual relationships between spatiotemporal variables and initial acceleration sprint performance in elite rugby backs, and to establish a normative data set of relevant strength-based measures. Methods: First, the spatiotemporal variables, step length / step rate and contact time / flight time ratios and initial acceleration performance were obtained from 35 elite male rugby backs (mean ± SD: age 25 9 ± 3 years) over the first four steps of three sprints. Angular and linear kinematic aspects of technique and strength-based qualities were collected from 25 of these participants. Secondly, the same spatiotemporal variables were collected from 19 of the participants on three further occasions (12 trials in total) to determine the within-individual associations of these variables and initial acceleration performance. Results: Moderate to very large meaningful within individual relationships (ǀrǀ = 0.43 to 0.88) were found between spatiotemporal variables and initial acceleration performance in 17 of the 19 participants. From these relationships, a theoretically ‘desirable’ change in whole-body kinematic strategy was individually determined for each participant, and normative strength-based measures to contextualize these were established. Conclusions: Meaningful within-individual relationships are evident between sprint spatiotemporal variables and initial acceleration performance in elite rugby backs. Individualized approaches are therefore necessary to understand how aspects of technique relate to initial acceleration performance. This study provides an objective, evidence-based approach for applied practitioners to identify the initial acceleration technical needs of individual rugby backs

EFFECTS OF TRYING TO GAIN DISTANCE ON GOLF DRIVING TECHNIQUE

Previous biomechanical research of the golf swing has shown segment separation of the shoulders and hips aids ball velocity. The purpose of the current study was to examine how the swing may differ when “trying” to gain extra distance in a game specific situation and whether an increase in launch velocity was achievable. A single subject design was employed with kinematic data (200 Hz) and ball characteristics collected using Trackman Pro launch monitor (ISG A/S, Denmark). Segment separation of the shoulder and hips (X-Factor and X-Factor stretch) and maximum endpoint velocity of the left hip, shoulder and elbow showed a significant difference between conditions, although mean launch velocity did not. This finding shows although the subject was able to produce greater endpoint velocity, performance improvement did not occur