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

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

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

The effect of the bend on technique and performance during maximal effort sprinting

This study investigated changes in performance and technique that occur during maximal effort bend sprinting compared to straight-line sprinting under typical outdoor track conditions. Utilising a repeated measures design, three-dimensional video analysis was conducted on seven male sprinters in both conditions (bend radius: 37.72 m). Mean race velocity decreased from 9.86 m/s to 9.39 m/s for the left step (p = 0.008) and from 9.80 m/s to 9.33 m/s for the right step (p = 0.004) on the bend compared to the straight, a 4.7% decrease for both steps. This was due mainly to a 0.11 Hz (p = 0.022) decrease in step frequency for the left step and a 0.10 m (p = 0.005) reduction in race step length for the right step. The left hip was 4.0° (p = 0.049) more adducted at touchdown on the bend than the straight. Furthermore, the bend elicited significant differences between left and right steps in a number of variables including ground contact time, touchdown distance and hip flexion/extension and abduction/adduction angles. The results indicate that the roles of the left and right steps may be functionally different during bend sprinting. This specificity should be considered when designing training programmes

Relationships between lower-limb kinematics and block phase performance in a cross section of sprinters

This study investigated lower-limb kinematics to explain the techniques used to achieve high levels of sprint start performance. A cross-sectional design was used to examine relationships between specific technique variables and horizontal external power production during the block phase. Video data were collected (200 Hz) at the training sessions of 16 sprinters who ranged in 100 m personal best times from 9.98 to 11.6 s. Each sprinter performed three 30 m sprints and reliable (all intraclass correlation coefficients, ICC(2,3) ≥ 0.89) lower-limb kinematic data were obtained through manual digitising. The front leg joints extended in a proximal-to-distal pattern for 15 sprinters, and a moderate positive relationship existed between peak front hip angular velocity and block power (r = 0.49, 90% confidence limits = 0.08–0.76). In the rear leg, there was a high positive relationship between relative push duration and block power (r = 0.53, 90% confidence limits = 0.13–0.78). The rear hip appeared to be important; rear hip angle at block exit was highly related to block power (r = 0.60, 90% confidence limits = 0.23–0.82), and there were moderate positive relationships with block power for its range of motion and peak angular velocity (both r = 0.49, 90% confidence limits = 0.08–0.76). As increased block power production was not associated with any negative aspects of technique in the subsequent stance phase, sprinters should be encouraged to maximise extension at both hips during the block phase

Assessing rugby place kick performance from initial ball flight kinematics: development, validation and application of a new measure

The appropriate determination of performance outcome is critical when appraising a performer’s technique. Previous studies of rugby place kicking technique have typically assessed performance based on ball velocity, but this is not the sole requirement. Therefore, a mathematical model of rugby place kick ball flight was developed to yield a single measure more representative of true performance. The model, which requires only initial ball flight kinematics, was calibrated and validated using empirical place kick data, and found to predict ball position with a mean error of 4.0% after 22 m of ball flight. The model was then applied to the performances of 33 place kickers. The predicted maximum distance, a single performance measure which accounted for initial ball velocity magnitude and direction, and spin, was determined using the model and was compared against ball velocity magnitude. A moderate association in the rank-order of the kicks between these two measures (ρ = 0.52) revealed that the relative success of the kicks would be assessed differently with each measure. The developed model provides a representative measure of place kick performance that is understandable for coaches, and can be used to predict changes in performance outcome under different ball launch or environmental conditions

Analysis of lower limb internal kinetics and electromyography in elite race walking.

The aim of this study was to analyse lower limb joint moments, powers and electromyography patterns in elite race walking. Twenty international male and female race walkers performed at their competitive pace in a laboratory setting. The collection of ground reaction forces (1000 Hz) was synchronised with two-dimensional high-speed videography (100 Hz) and electromyography of seven lower limb muscles (1000 Hz). As well as measuring key performance variables such as speed and stride length, normalised joint moments and powers were calculated. The rule in race walking which requires the knee to be extended from initial contact to midstance effectively made the knee redundant during stance with regard to energy generation. Instead, the leg functioned as a rigid lever which affected the role of the hip and ankle joints. The main contributors to energy generation were the hip extensors during late swing and early stance, and the ankle plantarflexors during late stance. The restricted functioning of the knee during stance meant that the importance of the swing leg in contributing to forward momentum was increased. The knee flexors underwent a phase of great energy absorption during the swing phase and this could increase the risk of injury to the hamstring muscles

Phase analysis in maximal sprinting: an investigation of step-to-step technical changes between the initial acceleration, transition and maximal velocity phases

The aim of this study was to investigate spatiotemporal and kinematic changes between the initial acceleration, transition and maximum velocity phases of a sprint. Sagittal plane kinematics from five experienced sprinters performing 50-m maximal sprints were collected using six HD-video cameras. Following manual digitising, spatiotemporal and kinematic variables at touchdown and toe-off were calculated. The start and end of the transition phase were identified using the step-to-step changes in centre of mass height and segment angles. Mean step-to-step changes of spatiotemporal and kinematic variables during each phase were calculated. Firstly, the study showed that if sufficient trials are available, step-to-step changes in shank and trunk angles might provide an appropriate measure to detect sprint phases in applied settings. However, given that changes in centre of mass height represent a more holistic measure, this was used to sub-divide the sprints into separate phases. Secondly, during the initial acceleration phase large step-to-step changes in touchdown kinematics were observed compared to the transition phase. At toe-off, step-to-step kinematic changes were consistent across the initial acceleration and transition phases before plateauing during the maximal velocity phase. These results provide coaches and practitioners with valuable insights into key differences between phases in maximal sprinting