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This study aimed to investigate inter- and intra-athlete technique variability in pre-elite and elite Australian fast bowlers delivering new ball conventional swing bowling. Ball grip angle and pelvis, torso, shoulder, elbow, wrist, upper arm, forearm, and hand kinematics were investigated at the point of ball release for inswing and outswing deliveries. Descriptive evaluations of group and individual data and k-means cluster analyses were used to assess inter- and intra-bowler technique variability. Inter-athlete technique and ball grip variability were identified, demonstrating that skilled bowlers use individualised strategies to generate swing. Functional movement variability was demonstrated by intra-athlete variability in successful swing bowling trials. Bowlers demonstrated stable technique parameters in large proximal body segments of the pelvis and torso, providing a level of repeatability to their bowling action. Greater variation was observed in bowling arm kinematics, allowing athletes to manipulate the finger and ball position to achieve the desired seam orientation at the point of ball release. This study demonstrates that skilled bowlers use individualised techniques and grips to generate swing and employ technique variations in successive deliveries. Coaches should employ individualised training strategies and use constraints-led approaches in training environments to encourage bowlers to seek adaptive movement solutions to generate swing. [ABSTRACT FROM AUTHOR]

Context: Hip pain is associated with reduced hip muscle strength, range of movement (ROM), and decreased postural stability. Singleleg squat is a reliable and valid method to measure dynamic balance. Objective: To evaluate the influence of physical characteristics and use of a decline board on squat performance in a hip pain population. Design: Cross-sectional study setting. Clinical Patients: In total, 33 individuals scheduled for arthroscopic hip surgery were matched with 33 healthy controls. Interventions: Hip and ankle ROM, hip strength, and trunk endurance were assessed, along with knee and trunk kinematics during squat on flat and 25° decline surfaces. Main Outcome Measures: Between-group and surface differences in alignment, between-group strength and ROM, and associations between alignment and physical characteristics were assessed and determined using mixed model analysis of variance and Pearson R. Results: The hip pain group had significantly less strength and ROM for all directions except abduction strength and ankle dorsifiexion (P > .02). No differences existed between lire 2 groups for trunk (P < .70) or knee displacement (P < .46) during squat on either surface. When the 2 groups were combined (n = 66), decline squat significantly reduced knee medial displacement in both limbs by approximately 1 cm (P < .01). Decline squat reduced uxink lateral movement on 1 side only (P = .03). Reduced knee displacement during decline squat showed fair association with less hip-extension strength (r = -29), hip-flexion strength (r = -.25), and less dorsifiexion (r = -.24). Strength and range were not associated with trunk displacement. Conclusions: Decline squat reduced medial knee and lateral trunk displacement regardless of hip pain. Reductions may be greater in those with lesser hip muscle strength and dorsifiexion. Use of a decline board during squat for improving knee and trunk alignment should be considered as a goal of exercise intervention. [ABSTRACT FROM AUTHOR]

The effect of complex training (CT) session design on acute postactivation performance enhancement (PAPE) of loaded jump squat(s) (JS) and ballistic bench throw(s) (BBT) was examined. This study further investigated whether relative strength is a moderating factor in PAPE in response to 3 distinct CT protocols. Fourteen Australian Football League (AFL) Academy athletes performed 3 different protocols comprising 85% 1 repetition maximum (1RM) back squats and bench press, and 30% 1RM loaded JS and BBT, differing in the sequencing of exercise order (i.e., complex pairs performed in isolation or with additional exercise interspersed within the intracomplex recovery period) and duration of the intracomplex recovery (2.5, 5, or 15 minutes). Differences in JS and BBT performance between CT protocols were trivial except for JS eccentric depth and eccentric impulse where small to moderate substantial differences were observed between protocols 2 and 3 in various sets; a small difference was observed between protocols 1 and 3 for eccentric depth. Small differences between protocols 1 and 2 were observed in set 1 in BBT peak velocity (ES= -20.26) and peak power (W·kg-1 ) (ES =-0.31). Small magnitudes of PAPE and decrements in performance were observed in some variables within protocols, yet effects across sets were inconsistent. Relative strength was negatively associated with JS performance (i.e., stronger athletes demonstrated a lower magnitude of PAPE) yet positively associated with PAPE of BBT peak force (N·kg-1 ) and peak power (W·kg-1 ). Alternating lower-body and upper-body complex sets and performance of ancillary exercise within the intracomplex recovery does not contribute to cumulative fatigue throughout the session and does not detrimentally affect subsequent JS and BBT performance. The manipulation of complex-set sequences offers practitioners a timeefficient means of providing both lower-body and upper-body heavy-resistance and ballistic training stimuli to achieve chronic training adaptations in maximal strength and power, with targeted improvements in specific kinetic and kinematic variables. [ABSTRACT FROM AUTHOR]

The effect of variable load jump squats (JSs) on acute drop jump (DJ) performance across multiple sets was examined. Seventeen elite rugby sevens athletes performed 3 DJs after 3 repetitions of a JS conditioning activity (CA) performed at 30 or 50% 1RM back squat loads. Acute postactivation performance enhancement (PAPE) in DJ kinetic and kinematic variables was assessed using a commercially available force platform (1,000 Hz). Postactivation performance enhancement was predominant after the 30% 1RM load with the greatest frequency of potentiation exhibited in set 3. The 50% 1RM CA resulted in substantial decrements in DJ performance with the exception of active stiffness, reactive strength index (flight:contact time), and contact time. Moderate differences were observed between the 50 and 30% 1RM loads for peak power (W), impulse (N·s), and force at zero velocity (N); active stiffness was the only variable where PAPE was greater in the 50% 1RM CA (ES: small). Active stiffness was the only variable to display favorable associations with relative strength in both the JS 30% 1RM (ES: 0.38 ± 0.20; moderate) and 50% 1RM (ES: 0.24 ± 0.23; small) CA loads. The JS 30% 1RM CA results in greater magnitude and frequency of PAPE of DJ kinetic and kinematic variables and is recommended if seeking to target PAPE in a range of DJ performance variables. Heavier JS loads may be appropriate if enhancement of muscle stiffness and stretch-shortening cycle efficiency is required. Consideration of targeted kinetic and kinematic variables when selecting CA intensity in complex training design is recommended. [ABSTRACT FROM AUTHOR]

Context: It is important to validate single-leg squat visual rating criteria used in clinical practice and research. Foot orthoses may improve single-leg squat performance in those who demonstrate biomechanics associated with increased risk of lower limb injury. Objective: Validate visual rating criteria proposed by Crossley et al, by determining whether athletes rated as poor single-leg squat performers display different single-leg squat biomechanics than good performers; and evaluate immediate effects of foot orthoses on single-leg squat biomechanics in poor performers. Design: Comparative cross-sectional study. Setting: University laboratory. Participants: 79 asymptomatic athletes underwent video classification of single-leg squat performance based on established visual rating criteria (overall impression, trunk posture, pelvis "in space," hip movement, and knee movement), and were rated as good (n = 23), fair (n = 41), or poor (n = 15) performers. Intervention: A subset of good (n = 16) and poor (n = 12) performers underwent biomechanical assessment, completing 5 continuous single-leg squats on their dominant limb while 3-dimensional motion analysis and ground reaction force data were recorded. Poor performers repeated the task standing on prefabricated foot orthoses. Main Outcome Measures: Peak external knee adduction moment (KAM) and peak angles for the trunk, hip, knee, and ankle. Results: Compared with good performers, poor performers had a significantly lower peak KAM (mean difference = 0.11 Nm/kg, 95% confidence interval = 0.02 to 0.2 Nm/kg), higher peak hip adduction angle (−4.3°, −7.6° to −0.9°), and higher peak trunk axial rotation toward their stance limb (3.8°, 0.4° to 7.2°). Foot orthoses significantly increased the peak KAM in poor performers (−0.06 Nm/kg, −0.1 to −0.01 Nm/kg), with values approximating those observed in good performers. Conclusions: Findings validate Crossley et al's visual rating criteria for single-leg squat performance in asymptomatic athletes, and suggest that "off-the-shelf" foot orthoses may be a simple intervention for poor performers to normalize the magnitude of the external KAM during single-leg squat. [ABSTRACT FROM AUTHOR]

Overarm throwing is an essential fundamental movement skill (FMS). Competency in throwing is critical to encourage physical activity throughout lifespan. However, the segmental sequencing characteristics of skilled throwing to achieve maximum ball release speed are unclear. Further, the standard instructions for segmental sequencing in coaching manuals are anecdotal and not based on scientific evidence. Therefore, the aim of this study was to establish the critical features of upper‐body sequencing in skilled throwing for maximum speed. This would enable revised instructions for coaching throwing based on scientific evidence. The three‐dimensional kinematics of 144 right‐handed unconstrained maximum overarm throws were captured and analyzed. The quartiles of participants with the fastest and lowest ball release speed, normalized by height, were defined as the Skilled Group and Less Skilled Group, respectively. Paired t‐tests were used to determine the differences in times of successive events within groups and independent t‐tests for between‐group differences in temporal space between events for all sequences. A characteristic segmental sequence of each group was defined as a sequence with significant within‐group differences in two successive events (p < 0.001), while a critical segmental sequence was defined as a sequence with significant differences in temporal space both within groups and between groups (p < 0.001). The Skilled Group had six characteristic sequences, while two were found for the Less Skilled Group, summarized in the conceptual model. A single critical sequence of non‐throwing arm elbow extension prior to shoulder extension was found. Five evidence‐based instructions were recommended to add to the Australian FMS instruction manual. [ABSTRACT FROM AUTHOR]

Analysing player kinematics during a match using "gold-standard" 3D video-based motion analysis techniques is a difficult prospect indeed. The development of small, wireless, wearable sensors offers the potential to reduce the challenges of measuring kinematics during match-play without hindering performance. The present study examined the viability of using wireless tri-axial accelerometers to examine whether key performance measures of drag flicks executed by expert specialist drag-flickers are predicted by the kinematics of the striking phase. Linear mixed models were used to examine whether the speed and accuracy of players' drag flicks were predicted by the duration of stick-ball contact, and the kinematics of the lead lower limb at stick-ball contact and ball release. Results revealed that stick and lead lower limb kinematics significantly predicted shot accuracy but not shot speed. Shorter drag-time predicted more accurate flicks (p = 0.03) as did a more vertical leg at stick-ball contact (p = 0.016) and a more horizontal thigh at ball release (p = 0.001). This may indicate that there are more ways to produce fast drag flicks than accurate ones. This study illustrates that wireless tri-axial accelerometers can be used on-field to measure the effects of kinematics on key performance measures. [ABSTRACT FROM AUTHOR]

Accurate kicking is essential to team success in Australian football. It is not known how foot-ball impact characteristics influence kicking accuracy, nor is it known if variability in foot-ball impact characteristics is functional or dysfunctional to performance. The aim of this study was to identify the relationship between foot-ball impact characteristics and kicking accuracy and determine if variability in foot-ball impact characteristics influenced performance variability. Ten players performed 30 drop punt kicks toward a target with an Australian football ball. Kicking accuracy (measured as the horizontal distance from the target in the perpendicular direction of the kick), initial ball flight characteristics, and foot-ball impact characteristics, including a novel method to calculate impact location on the ball, were measured. Variability was indicated using standard deviation of foot-ball impact and ball flight characteristics. Multiple linear regression analysis identified azimuth ball flight trajectory as the most important ball flight characteristic influencing kicking accuracy, not ball flight characteristics associated with ball curve. Intra-individual multiple linear regressions identified azimuth ball impact location and foot-ball angle were the two most important factors explaining variance in azimuth ball flight trajectory, the chosen performance measure. Variability existed between and within players. Reduced variability in azimuth ball flight trajectory, the chosen performance measure, was associated with reduced variability in foot-ball impact characteristics. This result indicated variability in foot-ball impact characteristics was dysfunctional for performance in the analysed task. Foot-ball impact characteristics and variability in foot-ball impact characteristics influences accuracy of Australian football drop punt kicking. [ABSTRACT FROM AUTHOR]

The purpose of this study was to probe the sex-based differences in the stroke and movement dynamics of Grand Slam hard-court tennis. Player and ball tracking data were collated for 102 male and 95 female players during the 2012–2014 Australian Open tournaments. Serve, serve return, groundstroke and movement data were compared between sexes. Serve statistics were the subject of the largest differences, with males achieving significantly faster speeds, aces and unreturned serves while also winning a greater percentage of service points. When returning serve, women contacted the ball closer to the net, lower to the ground and achieved flatter ball trajectories than males. Groundstroke frequencies were similar between sexes, although males hit with greater speed, flatter trajectories and impacted more shots inside the baseline. Distance covered per set or during points won or lost was not sex dependent, yet men exhibited faster average movement speeds. These findings highlight the need for sex-specific training and practice designs that cater to the different stroke dynamics, particularly in relation to the first serve and serve-return, as well as movement speeds. [ABSTRACT FROM PUBLISHER]

Background and purpose The objective of this study is to compare the balance and gait of 11 people with multiple sclerosis (MS) to 11 healthy controls and to investigate the immediate change after a single intervention based on the Bobath concept on these activities in the MS group. Methods Balance was assessed by ground reaction forces (GRF) and centre of pressure movements during single limb standing (SLS), the Lateral Reach Test (LRT) and the Four Square Step Test (FSST). Gait was evaluated by GRF, ankle kinematics and spatiotemporal measures. Results Baseline measures in the MS group showed significantly greater vertical GRF variability ( p = 0.008) during SLS reached less distance on the LRT ( p = 0.001) and were slower completing the FSST ( p < 0.001). During gait, the MS group walked slower ( p = 0.005) and had less ankle plantarflexion (PF) ( p = 0.001) than the control group. Less peak vertical GRF ( p < 0.001) and peak propulsive GRF ( p = 0.004) at terminal stance and increased vertical GRF in midstance ( p = 0.005) were observed. The measures of balance and gait were re-assessed in the MS group immediately after a 20-min intervention based on the Bobath concept delivered to the most impaired foot and ankle. After the intervention, the MS group had significant changes towards the control group values with reduced mediolateral ( p = 0.002) and vertical ( p = 0.016) GRF variability in the SLS task, faster FSST time ( p = 0.006) and increased ankle PF during gait ( p = 0.002). Discussion This study provides further evidence of balance and gait limitations in people with MS and indicates that a single treatment based on principles of the Bobath concept to the foot and ankle can result in immediate improvements in balance and ankle PF during gait in people with MS. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The punt kick is a fundamental skill used in several team sports; however, there has been a lack of research on how fatigue affects its technique. The purpose of this study was to determine the effects of short-term fatigue on punt-kicking performance. Eight elite and sub-elite Australian Football players performed maximal drop punt kicks on their preferred leg prior to, during and after a match-specific fatigue protocol. Optotrak Certus collected kinematic data from kick foot toe-off until ball contact. Repeated-measures analysis of variance showed a significant increase in 20 m sprint times after each short-term protocol, indicating fatigue. Foot speed did not significantly change with fatigue; however, increases in the range of motion at the pelvis and kicking thigh, along with increases in kicking thigh angular velocity, occurred. For the support leg, maximum knee flexion angular velocity increased while there was greater flexion found at the knee and hip, and greater range of motion at the knee. Players are able to make kinematic adaptations in order to maintain foot speed while punting for maximal distance after short-term efforts. [ABSTRACT FROM AUTHOR]

This study examined the perceived effort, success rates and kinematics for three push strategies in a simulated lateral patient transfer (horizontal slide). Thirteen healthy subjects (four males) completed three repetition pushing loads of 6, 10 and 14 kg in random order; with a spontaneous push strategy, then with a straight-back bent-knees (squat) strategy and the preparatory pelvic movement (‘rockback’) strategy in random order. Perceived effort and kinematic parameters measured at the onset of movement and at maximum push excursion were compared between strategies and between loads with repeated measures ANOVA. The spontaneous and ‘rockback’ strategies achieved the pushing task with less perceived effort across all loads than the squat push (P < 0.001). Only 3/13 participants were successful on all attempts at pushing the 14 kg load using a squat strategy, which contrasted with 12/13 participants when the spontaneous strategy or the ‘rockback’ strategy was used. Forward movement of the pelvis and forward trunk inclination may be positively associated with lower perceived effort in the push task. Practitioner Summary:In a manual-handling task that simulated a lateral patient transfer (horizontal slide), perceived effort and success rates of three push strategies were compared. A straight-back bent-knees push (squat) strategy demonstrated greater perceived effort and lower success rates than a spontaneous push strategy, or a push strategy with preparatory ‘rockback’ pelvic movement. [ABSTRACT FROM AUTHOR]

Eccentric contractions that provide spring energy can also cause muscle damage. The aim of this study was to explore leg and vertical stiffness following muscle damage induced by an eccentric exercise protocol. Twenty active males completed 60 minutes of backward-walking on a treadmill at 0.67 m/s and a gradient of − 8.5° to induce muscle damage. Tests were performed immediately before; immediately post; and 24, 48, and 168 hours post eccentric exercise. Tests included running at 3.35 m/s and hopping at 2.2 Hz using single- and double-legged actions. Leg and vertical stiffness were measured from kinetic and kinematic data, and electromyography (EMG) of five muscles of the preferred limb were recorded during hopping. Increases in pain scores (over 37%) occurred post-exercise and 24 and 48 hours later (p < 0.001). A 7% decrease in maximal voluntary contraction occurred immediately post-exercise (p = 0.019). Changes in knee kinematics during single-legged hopping were observed 168 hours post (p < 0.05). No significant changes were observed in EMG, creatine kinase activity, leg, or vertical stiffness. Results indicate that knee mechanics may be altered to maintain consistent levels of leg and vertical stiffness when eccentric exercise-induced muscle damage is present in the lower legs. [ABSTRACT FROM PUBLISHER]