IDENTIFYING THE KEY TECHNICAL ASPECTS OF RUGBY PLACE KICKING: A QUALITATIVE CASE STUDY OF AN ELITE COACH

Place kicking plays an important role in the outcome of rugby union matches. However, the understanding of rugby place kicking technique is currently limited and this study aimed to start ‘bridging the gap’ between contemporary coaching expertise and the biomechanical understanding of rugby place kicking. An Interpretive Phenomenological Analysis of a semi-structured interview with an elite kicking coach was used to identify the key technical features of rugby place kicking and thus provide direction for future biomechanical research. Ball placement, the approach, body position at support leg contact, support leg mechanics, the path of the foot during the kicking phase and its orientation at ball contact, energy dissipation during the follow through, and overriding coordination issues were all identified as key areas in need of future research

ANTHROPOMETRIC AND STRENGTH CHARACTERISTICS OF RUGBY PLACE KICKERS

The musculoskeletal demands of rugby place kicking are of interest to coaches from both a performance and an injury perspective. Specific musculoskeletal model inputs are required to accurately investigate these demands. This study determined selected anthropometric and strength characteristics of professional and amateur place kickers from photo-based measurements and vertical jumps. All segmental inertia characteristics were similar between the two groups aside from the torso moment of inertia. Professional players displayed superior jump strength measures compared with the amateurs. The kickers' inertia and strength characteristics also differed from commonly used values obtained from physically active males and male soccer players. Careful consideration of input parameters is required when developing musculoskeletal models of rugby kickers

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 joint kinetic analysis of rugby place kicking technique to understand why kickers achieve different performance outcomes

We aimed to identify differences in kicking leg and torso mechanics between groups of rugby place kickers who achieve different performance outcomes, and to understand why these features are associated with varying levels of success. Thirty-three experienced place kickers performed maximum effort place kicks, whilst three-dimensional kinematic (240 Hz) and ground reaction force (960 Hz) data were recorded. Kicking leg and torso mechanics were compared between the more successful (‘long’) kickers and two sub groups of less successful kickers (’short’ and ‘wide-left’) using magnitude-based inferences and statistical parametric mapping. Short kickers achieved substantially slower ball velocities compared with the long kickers (20.8 ± 2.2 m/s vs. 27.6 ± 1.7 m/s, respectively) due to performing substantially less positive hip flexor (normalised mean values = 0.071 vs. 0.092) and knee extensor (0.004 vs. 0.009) joint work throughout the downswing, which may be associated with their more front-on body orientation, and potentially a lack of strength or intent. Wide-left kickers achieved comparable ball velocities (26.9 ± 1.6 m/s) to the long kickers, but they were less accurate due to substantially more longitudinal ball spin and a misdirected linear ball velocity. Wide-left kickers created a tension arc across the torso and therefore greater positive hip flexor joint work (normalised mean = 0.112) throughout the downswing than the long kickers. Whilst this may have assisted kicking foot velocity, it also induced greater longitudinal torso rotation during the downswing, and may have affected the ability of the hip to control the direction of the foot trajectory

WITHIN-SUBJECT REPEATABILITY AND BETWEEN-SUBJECT VARIABILITY IN POSTURE DURING CALIBRATION OF AN INERTIAL MEASUREMENT UNIT SYSTEM

Inertial measurement units (IMUs) are a valuable tool for field based sports research, but within- and between-subject comparisons may be affected by variation in the 0° position established by a standing calibration position. This study assessed within-subject repeatability and between-subject variability in IMU sensor orientations during calibration. Calibration posture was reliable within-subjects given standardised instructions (typical error \u3c 1.9°). Sensor angles relative to a global vertical axis had large between-subject ranges for upper spine (21–35°), lower spine (1–23°) and pelvis (11–35°), while lower limb segment angles had much lower variability (0-6°). Thus, a standing calibration posture is repeatable within participants given suitable instructions, however variability in standing posture may need to be accounted for before making between-subject comparisons, particularly with regard to spine and pelvis segments

A COMPARISON OF TRUNK AND SHANK ANGLES BETWEEN ELITE AND SUB-ELITE SPRINTERS DURING SPRINT ACCELERATION

Acceleration is a movement that requires skilful positioning of the body to apply force in the desired direction. The sagittal plane orientation of the trunk and shank are features that coaches use to visually assess sprint acceleration technique. This study examined differences in trunk and shank angles between elite and sub-elite sprinters during early acceleration using inertial sensors. Elite sprinters exhibited more vertical trunk positions throughout all four steps compared to sub-elite with moderate to very large differences at discrete events (d = 0.79 - 2.16). Shank angles were more vertical at touchdown in sub-elite compared to elite sprinters (d = -0.70 - -0.39), but similar at toe-off. These results suggest that less horizontal trunk lean during acceleration is a feature of higher level sprinters, coaches should be conscious of this when giving technical feedback

Modeling the stance leg in two-dimensional analyses of sprinting:Inclusion of the MTP joint affects joint kinetics

Two-dimensional analyses of sprint kinetics are commonly undertaken but often ignore the metatarsalphalangeal (MTP) joint and model the foot as a single segment. Due to the linked-segment nature of inverse dynamics analyses, the aim of this study was to investigate the effect of ignoring the MTP joint on the calculated joint kinetics at the other stance leg joints during sprinting. High-speed video and force platform data were collected from four to five trials for each of three international athletes. Resultant joint moments, powers, and net work at the stance leg joints during the first stance phase after block clearance were calculated using three different foot models. By ignoring the MTP joint, peak extensor moments at the ankle, knee, and hip were on average 35% higher (p .05), respectively, than those calculated with the MTP joint included. Peak ankle and knee joint powers and net work at all joints were also significantly (p < .05) different. By ignoring a genuine MTP joint plantar flexor moment, artificially high peak ankle joint moments are calculated, and these also affect the calculated joint kinetics at the knee

Measurement Error in Estimates of Sprint Velocity from a Laser Displacement Measurement Device

This study aimed to determine the measurement error associated with estimates of velocity from a laser-based device during different phases of a maximal athletic sprint. Laser-based displacement data were obtained from 10 sprinters completing a total of 89 sprints and were fitted with a fifth-order polynomial function which was differentiated to obtain instantaneous velocity data. These velocity estimates were compared against criterion high-speed video velocities at either 1, 5, 10, 30 or 50 m using a Bland-Altman analysis to assess bias and random error. Bias was highest at 1 m (+ 0.41 m/s) and tended to decrease as the measurement distance increased, with values less than + 0.10 m/s at 30 and 50 m. Random error was more consistent between distances, and reached a minimum value (±0.11 m/s) at 10 m. Laser devices offer a potentially useful time-efficient tool for assessing between-subject or between-session performance from the mid-acceleration and maximum velocity phases (i. e., at 10 m and beyond), although only differences exceeding 0.22-0.30 m/s should be considered genuine. However, laser data should not be used during the first 5 m of a sprint, and are likely of limited use for assessing within-subject variation in performance during a single session

RECTUS FEMORIS MECHANICS IN RUGBY KICKING

This study aimed to quantify rectus femoris muscle-tendon unit length and excitation during different types of rugby kick. Seven male rugby players completed a series of kicks during which kinematic and muscle excitation data were collected. Between 0.2 and 0.1 s prior to ball contact in all kick types, the rectus femoris lengthened rapidly whilst muscle excitation also rapidly increased, identifying eccentric action as a possible mechanism for muscle strain injury. Peak rectus femoris muscle excitations occurred later in the kicks with a primary height demand, and differences in the timing of peak muscle excitation existed between different regions of the rectus femoris muscle. This study provides information which can be used to inform the specificity of physical preparation and rehabilitation protocols for rugby kickers