Ankle mechanics during jump landings across different foot positions in professional ballet dancers.

This study aimed to investigate the effect foot position on ankle joint mechanics and vertical ground reaction forces (vGRF) across jump landings in professional ballet dancers. Twenty-seven professional ballet dancers (men: 14; women: 13) attended one data collection session, completing five maximal countermovement jumps in parallel, first, second, fourth, and fifth positions. Three-dimensional ankle mechanics, landing vGRF variables, and jump height were recorded via a seven-camera motion capture system and one force platform. A repeated measures multivariate analysis of variance was used to assess the main effects foot position across all target variables. A linear discriminate analysis was conducted to investigate target variables across foot positions. Frontal and transverse plane ankle mechanics had the largest impact when discriminating between foot positions. Ankle power in the transverse plane during jump landing in fourth was double that of all other positions. Our findings suggest that ankle range of motion should be restored before returning to jumps in fourth and fifth positions following distal lower extremity injury. The multiplanar energy transfer observed indicates a need for specific exercises to develop multiplanar force and rate of force development of local structures around the ankle.

The association of range of motion, lower limb strength, and load during jump landings in professional ballet dancers.

This study aimed to investigate the associations between peak plantarflexion ankle joint moments and vertical ground reaction forces (vGRF) during jump landings, and static ankle dorsiflexion range of motion (ROM), three-dimensional ankle excursions, and lower extremity strength in professional ballet dancers. Twenty-seven professional ballet dancers volunteered to participate (men = 14, women = 13). Participants attended one data collection session to measure dorsiflexion ROM and isometric lower extremity strength. Two further sessions were used to establish ankle mechanics and vGRFs during countermovement jump landings in seven foot positions, via a seven-camera motion capture system and piezoelectric force platform. Two linear mixed-effects models were used to investigate associations between the target variables and strength, dorsiflexion ROM, and ankle excursions. Dancer identification, sex, and foot position were entered as random effects. Model fit, when considered independent of random effects, was generally poor with the predictor variables explaining little of the variance of peak plantarflexion ankle joint moments (R2 = 0.02) or vGRF (R2 = 0.01). Model fit improved when random effects were considered (R2 = 0.65 & 0.34). Frontal plane ankle excursion was the only predictor variable with a significant negative association with peak plantarflexion ankle joint moments (p = .016), although coefficient estimates were small. Strength, static ankle dorsiflexion ROM, and three-dimensional ankle excursions are poor predictors of load experienced at a joint and system level in professional ballet dancers. Differences between individuals, sex, and foot position may be better indicators of the load experienced during jump landings.

Reliability of ankle mechanics during jump landings in turned-out and parallel foot positions in professional ballet dancers.

This study aimed to determine the within- and between-session reliability of ankle mechanics and vertical ground reaction forces (vGRF) during jump landings in turned-out and parallel foot positions in professional ballet dancers. Twenty-four professional ballet dancers (men = 13, women = 11) attended two data collection sessions where they completed five maximal countermovement jumps in each foot position. The ankle joint mechanics and vGRF of the right limb were recorded via a seven-camera motion capture system and one force platform. Within- and between-session intraclass correlation coefficients (ICC), coefficients of variation (CV), standard error of measurement, and minimal detectable change were calculated for three-dimensional ankle excursion, peak ankle angle, ankle joint velocity, moment, and power, as well as peak landing vGRF, time to peak landing vGRF, loading rate, and jump height. Across both foot positions, within- (ICC: 0.17-0.96; CV: 1.4-82.3%) and between-session (ICC: 0.02-0.98; CV:1.3-57.1%) reliability ranged from poor to excellent, with ankle excursion, peak ankle angle, and jump height demonstrating the greatest ICC values (ICC: 0.65-0.96; CV: 1.4-57%). Jump landings in a turned-out foot position demonstrated better within-session reliability compared to a parallel position, however, no difference in between-session reliability across the foot positions was observed. Most ankle mechanics provide adequate between-session, but not within-session, reliability during jump landings in professional ballet dancers.

A cross-sectional retrospective survey of injury situation and prevalence in female recreational netball players with a focus on knee injuries.

OBJECTIVES: To examine situations of injury and injury prevalence in female adult recreational netball players with a focus on knee injuries. DESIGN: Cross sectional retrospective online survey. PARTICIPANTS: 193 female adult recreational netball players. MAIN OUTCOME MEASURES: Any injury sustained in the previous 12 months, situation of injury, any knee injuries sustained in the previous five years, the length of time unable to play netball, and knee injury management. RESULTS: In the previous 12 months, 61% of respondents sustained injury to the lower limb, and 27% to the upper limb. Lower limb injury situations were mostly landings (46%). Upper limb injury situations were mostly collisions with an opponent (27%). 46% reported sustaining a knee injury in the previous five years. Following knee injury, players were unable to play netball for 6.8 ± 7.0 months (training); and 8.2 ± 7.4 months (matches) respectively. CONCLUSIONS: Lower limb injury is more common than upper limb injury in recreational adult female adult netball players. Landing was the most common situation of injury for the lower limb including knee injuries. In the previous five years, nearly half of the players had sustained a knee injury resulting in more than six months out of the game.

The effect of attentional focus instructions on performance and technique in a complex open skill.

External focus of attention has been shown to promote more automatic motor control, yielding better performance and more efficient technique, than an internal focus. However, most research has used closed-skill tasks in novices. The extent to which the reported pattern of findings generalises to more complex, time-constrained tasks requires further investigation. In this study, we investigated the effect of attentional focus instructions on performance and technique in an open-skill task in skilled performers. Thirteen skilled cricket batters batted from a ball projector in four conditions, receiving instructions to focus on the movement of their hands (internal focus), the movement of their bat (proximal external focus), the flight of the ball (distal external focus), or no instruction (control). Performance and technique were measured by quality of bat-ball contacts and step length/knee flexion, respectively, whilst playing straight drives. Compared to external focus and control conditions, focusing internally yielded significantly worse batting performance and shorter step lengths, with the largest effects observed between internal and distal external focus conditions. Quality of bat-ball contact data suggested that participants' ability to protect the wicket (as evidenced by more miss/edge shots) was more negatively affected by focusing internally than their ability to play shots to score runs (as evidenced by fewer good bat-ball contacts). Findings suggest that, for skilled performance of open-skill tasks, a distal external focus yields more effective performance and technique compared with focusing internally. Findings highlight the need for further research on attentional focus effects between different skills within specific sports.Highlights A distal external focus of attention enhances performance and technique of skilled cricket batters compared with an internal focus.Providing skilled batters with no instructions yields similar performance benefits to distal external focus instructions.Focusing internally differentially negatively affects skilled cricket batters depending on the strategic intention of the shot being played (e.g. protecting the wicket vs attempting to score runs).

The approach towards the ball, rather than the physical characteristics of the kicker, limits accurate rugby place kicking range.

The aim of this study was to understand how a place kicker's range is limited by their approach to the ball and their physical characteristics. Thirty-three kickers performed maximal place kicks and vertical jumps in a laboratory. Whole-body motion and ground reaction forces during the approach phase of the kicks, jump performance and anthropometric measurements of those whose predicted maximum distance was limited by range (n = 17) rather than accuracy were analysed. Principal component analysis (PCA) reduced the number of variables considered before stepwise regression analyses assessed variance in place kick maximum distance and associated criteria. Four components, explaining 94% of the variance in maximum distance, were extracted from the PCA: width of approach, anterior-posterior body position, centre-of-mass height and lower limb strength. Lower limb strength was a significant predictor of both kicking foot velocity (R2 = 0.55, p = 0.001) and ball velocity magnitude (R2 = 0.57, p < 0.001). However, maximum distance was determined by body position during the approach (antero-posterior position, R2 = 0.52, p = 0.001 and centre-of-mass height, R2 = 0.12, p = 0.049). This highlights the importance of considering three-dimensional motion of the kicker alongside their physical capabilities to understand place kicking range.

Situations and mechanisms of non-contact knee injury in adult netball: A systematic review.

OBJECTIVES: Noncontact knee injuries in netball are a concern due to a range of negative consequences. To reduce the number of injuries, identifying the situation and mechanism of injury is important. This systematic review examined the literature reporting the situation and mechanism of noncontact knee injury in netball. DESIGN: Systematic Review. METHODS: PRISMA guidelines were followed and specific key-term combinations used to search databases. Descriptive and analytic-observational studies reporting the situation or mechanism of noncontact knee injury in females playing netball were included (evaluated using frequency counts). RESULTS: Six articles were included (combined sample 11,401). Players self-reported the situation of injury in five studies, only one study reported both the situation and mechanism of injury. Landing was the most reported situation of knee injury, representing 46.6% of all knee injuries whilst knee abduction (valgus) collapse was the most observed mechanism. Situation and mechanism of noncontact knee injury in netball were not adequately reported. CONCLUSIONS: Despite the variations in reporting methods, landing is the most common situation of injury. As only one study reported mechanism of injury, it is difficult to draw conclusions but the mechanism of noncontact knee injury in netball appears similar to those identified in other female athletes.

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 ±â€¯2.2 m/s vs. 27.6 ±â€¯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 ±â€¯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.

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.

Kicking foot swing planes and support leg kinematics in rugby place kicking: Differences between accurate and inaccurate kickers.

Place kicking is a complex whole-body movement that contributes 45% of the points scored in international Rugby Union. This study compared the kicking foot swing plane characteristics of accurate and inaccurate kickers, underpinned by differences in their support leg and pelvis kinematics at support foot contact, to identify key technique characteristics. Motion capture data (240 Hz) were collected from 33 experienced kickers, and distinct groups of accurate (n = 18) and inaccurate (n = 8) kickers were identified based on their performance characteristics. All accurate kickers were capable of kicking successfully from at least 33.3 m, whereas all inaccurate kickers would have missed left from distances greater than 30.7 m. The accurate group exhibited a moderately shallower swing plane inclination (50.6 ± 4.8° vs. 54.3 ± 2.1°) and directed the plane moderately further to the right of the target (20.2 ± 5.4° vs. 16.7 ± 4.1°). At support foot contact, the accurate group placed their support foot moderately less far behind the ball (0.08 ± 0.08 m vs. 0.12 ± 0.04 m) and positioned their centre of mass moderately further to the support leg side (0.77 ± 0.07 m vs. 0.72 ± 0.01 m) due to a moderately greater stance leg lean (29.3 ± 4.1° vs. 26.8 ± 3.2°). The kicking foot swing plane is highly planar in rugby place kicking but its orientation differs between accurate and inaccurate kickers. These plane characteristics may be controlled by support foot placement and support leg and pelvis kinematics at support foot contact.