Ascertaining how racket orientation angle differences at ball-impact influence the accuracy of different squash strokes could assist player skill development and possibly reduce the number of unforced errors hit within a match. The purpose of this study was to identify differences in racket orientation angles of accurate and inaccurate forehand and backhand drive, volley and drop shots. A magnetic-inertial measurement unit embedded in a racket output orientation angles of twelve male junior players, with five accurate and five inaccurate shots per player per stroke analysed. Paired samples t-tests revealed that inaccurate backhand drop shots exhibited significantly (p < 0.05) less racket roll angle (racket face less open) at impact than accurate shots, indicating this parameter was a determining factor in the accuracy of this stroke. Racket orientation angle differences between accurate and inaccurate shots of the remaining strokes were too small to be used to distinguish shot accuracy. There was significantly greater variability in racket orientation angles during inaccurate forehand drop and backhand drive shots compared to accurate shots. These findings demonstrate how racket orientation angle differences at ball-impact can influence the accuracy of shots and highlights the need for consistent racket orientations to allow for an accurate shot.

Springboard diving training is often focused upon skill repetition to establish movement accuracy, stability and consistency. Within-participant study designs provide the ability to understand how individuals create these skills under different movement strategies. IMUs measured angular velocity time-series data of two athletes performing multiple repetitions of forward 31/2 somersault pike dives. Functional Principal Component Analyses (fPCA) were performed to examine individual movement structure and variability. The first five fPC's represented approximately 98% of the variability in angular velocity for both divers. To determine the relative importance of angular velocity variability, Pearson's correlations for pairwise comparisons were used to assess the relationship between fPC scores and discrete performance variables during takeoff, flight and entry. Divers exhibited a different number and types of significant correlations (International = 4; National = 11). Only one correlation was common for both divers; higher angular velocity during Initial Flight and/or Somersault phases resulted in more vertically aligned entry posture (International: fPC1 r = -0.761, p fPC3 r = -0.796, p < 0.01). Findings identify individualised angular velocity time-series structure and kinematic performance variables (International = angular; National = linear) that can be used by coaching/sport science teams to optimisation performance success.

The torso muscles play important roles in longitudinal rotation between the upper and lower torso on land but demands on these muscles at different swimming speeds and their role in torso twist in front crawl remains unclear. We aimed to compare torso muscle activity at different front crawl speeds and to assess the relationships between torso muscle activity and torso twist. Three-dimensional kinematics and torso muscle EMG data were collected from 15 male swimmers during middle-distance and sprint front crawl. Internal oblique, external oblique, and rectus abdominis, but not erector spinae, activities were greater at sprint than middle-distance pace. Sprint swimmers are likely to benefit from focusing training on the abdominal muscles. Cross-correlation peak coefficients between muscle activity and torso twist occurred with 517-775 and 400-600 ms lag at middle-distance and sprint paces (respectively). These lags are beyond the torso muscle electromechanical delay (similar to 220 ms) and are too long for these muscles to produce movement changes. Further, peak coefficients coincided with both positive and negative shifts, indicating that muscle activity did not always precede kinematic changes. The torso muscles are therefore likely to play a greater role in maintaining stability and controlling posture in front crawl than producing torso twist.

Objectives: To identify characteristics of jockey falls associated with high-risk landings using a modified Equestrian Fall Assessment Instrument.Design: Cross-sectional study.Methods: Video footage of 22 flat and 58 jump racing falls (N = 80) which occurred in Great Britain, Ireland, and New Zealand from 2013 to 2018 was systematically analysed using the modified Equestrian Fall Assessment Instrument. Race, horse, and jockey-level factors, including the nature of ground contact (landings), were characterised identifying factors associated with high-risk landings. High-risk landings refer to cases where the jockey's head impacted the ground or where there was potential horse impact on the jockey. A multivariable logistic regression model was applied identifying independent variables associated with high-risk landings. Results: In 79 % (63/80) of race falls examined, at least one high-risk landing factor was present. Three indepen-dent variables explained 40.3 % of variance in high-risk landings. Lower race class (odds ratio 1.5; 95 % confidence interval 0.96, 2.39; p = 0.054), hanging onto the reins upon ground impact (odds ratio 7.5; 95 % confidence interval 1.04, 53.63; p = 0.028), and no jockey tuck-and-roll behaviour following ground impact (odds ratio 4.9; 95 % confidence interval 1.65, 14.44; p = 0.001) were associated with high-risk landings.Conclusions: Jockeys who ride in lower race classes, who hung onto the reins before landing, and who didn't tuck -and-roll during a fall had increased risk of a high-risk landing. Further examination of relationships between race, jockey experience and fall behaviour characteristics upon injury outcomes, and evaluation of potential protective benefits of fall training are required.(c) 2022 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Background: From retrospective research, it is believed that children who predominantly spend their time shod have poorer foot strength and performance than those who are predominantly barefoot. Children's foot motion has been shown to be adversely affected by standard school shoes; however, the long-term effect of moderate minimalist shoes on foot strength, muscle structure and balance in children is unknown.& nbsp;Research question: Does wearing moderate minimalist shoes, compared to stiff shoes, benefit a child's foot strength, muscle structure and performance over time?& nbsp;Methods: Seventy healthy children (9-12 yr) were randomly assigned to wear standard (control), or minimalist shoes (experimental) at school, for nine months. Cross-sectional areas (CSA) of Abductor Hallucis (AH) and Flexor Digitorum Brevis (FDB) muscles, and toe flexor strength (TFS) of hallux and lesser toes separately, were primary outcome measures. Single leg balance (SLB), Y-balance test (YBT) and standing long jump (SLJ) were secondary outcome measures. Pre-and post-intervention measurements were analysed for between group differences with ANCOVA.& nbsp;Results: Minimalist shoes resulted in moderate but statistically non-significant increases in muscle CSA (AH eta 2p =.04, FDB eta 2p =.05) and TFS (hallux eta 2p =.05, lesser toes eta 2p =.04). Significant moderate to large improvements in YBT in the experimental group were found in the postero-medial (P = .04, eta 2p =.07) and postero-lateral (P = .01, eta 2p =.10) directions. YBT (anterior, postero-medial and postero-lateral) was correlated with hallux TFS (R =.29,.27 and.33 respectively), lesser toes TFS (R =.28,.35 and.38 respectively) and SLJ (R =.30,.39 and.57 respectively). CSA of FDB was correlated with SLJ (R =.34) and SLB (R =.42).& nbsp;Significance: Wearing moderate minimalist shoes long-term improves balance in children. TFS is correlated with better balance and SLJ. Moderate minimalist school shoes are recommended for children.

Ecker, T. M., Bremer, A. K., Krause, F. G., M€ uller, T., & Weber, M. (2016). Prospective Use of a Standardized nonoperative early weightbearing protocol for achilles tendon rupture: 17 Years of experience. American Journal of Sports Medicine, 44, 1004–1010. https://doi. org/10.1177/0363546515623501 Frankewycz, B., Krutsch, W., Weber, J., Ernstberger, A., Nerlich, M., & Pfeifer, C. G. (2017). Rehabilitation of Achilles tendon ruptures: Is early functional rehabilitation daily routine? Archives of Orthopaedic and Trauma Surgery, 137, 333–340. https://doi.org/10.1007/s00402017-2627-9. McCormack, R., & Bovard, J. (2015). Early functional rehabilitation or cast immobilization for the postoperative management of acute Achilles tendon rupture? A systematic review and meta-analysis of randomized controlled trials. British Journal of Sports Medicine, 49, 1329–1335. https://doi.org/10.1136/bjsports-2015-094935

Cross‐country eventing is one of the highest‐risk sporting activities for serious injury outcomes. This study investigated relationships between fall characteristics and high‐risk falls at jumps in cross‐country eventing. A video analysis protocol was systematically developed to analyze 87 video recordings of high‐risk rider falls; defined as when the rider's head impacted the ground and/or where there was potential horse impact with the rider. Falls were classified according to competition type, jump type, horse‐related, and rider‐related factors. At least one high‐risk fall characteristic was observed in 45 of 87 examined falls. Multivariable best subsets regression identified five independent variables explaining 38.4% of the variance in the number of high‐risk falls. Increased likelihood of high‐risk falls was associated with continuation of horse direction or speed upon rider ground impact, higher jump approach speed, changes in rider body posture upon landing, rider air jacket usage, and reduced rider fall time. The Eventing Fall Assessment Instrument (EFAI) video analysis protocol (attached as supplementary material) facilitated systematic examination of multiple characteristics associated with high‐risk falls and identified likely influential characteristics. Based on EFAI and subsequent data analyses, findings suggest optimized approach speed for correct striding and take‐off; jump design to enable run‐out; and rider training could help reduce the occurrence of high‐risk falls. Air jacket usage and their design characteristics warrant further investigation.

Background: Speed-oriented power training with light intensities permits rapid acceleration at the beginning of each concentric phase, but necessitates significant deceleration in the later concentric phase to halt the motion. Force exertion and speed of muscle contraction are therefore delimited. To improve the concentric effort, ballistic actions using a Smith machine have been recommended (bench press throws and squat jumps etc). Typical Smith machines however allow vertical pushing exercises only. Hence, a new technique that mimics ballistic actions needs to be developed. In this study, an alternative technique, described as “thrust-back” has been introduced, where the spotter’s hands, rather than the lifter, halt the concentric motion. The effectiveness of thrust-back applied during fast bench press training on concentric velocity as well as gains in 1RM strength, power and power endurance was examined. Methods: Seventeen university students (12 males and 5 females), who abstained from chest exercises for 3~36 months, performed 15 repetitions of fast bench press at 30% 1RM with and without (control) thrust-back. Peak and mean concentric bar velocities were calculated using a string potentiometer. Subjects were then divided into two groups to undergo 8 weeks (16 sessions) of fast bench press training at 30% 1RM (15 repetitions×4~6sets) with or without thrust-back. One-RM, power and power endurance were evaluated before and after the training. Power and power endurance were estimated via the bar flight distances achieved during 20 repetitions of bench press throws at 30% 1RM on a Smith machine. Results: Thrust-back produced greater peak (up to +13%, P<0.001) and mean (up to +10%, P=0.026) concentric velocities than the control. After 8 weeks of implementation, the thrust-back training resulted in similar 1RM improvement to that of the control (+12.9 vs. +6.4%, P<0.001), but yielded greater improvements in the bar flight distances than the control (+13~37% vs. +4~13%, P=0.027). Moreover, the decline in the bar flight distances across 20 repetitions of bench press throws was attenuated after the thrust-back training (P=0.012), while the declining patter remained similar after the control training. Discussion: The augmented concentric velocity (and effort) via thrust-back technique did not magnify 1RM strength gain compared to the control training, however was successfully translated into greater gains in power and power endurance. When Smith machines are not available or not suited to perform the intended exercises, then thrust-back technique may become an alternative strategy since it can be applied to various exercise types. The authors declare no conflict of interest.

Background: Stronger toe flexor muscles improve performance outcomes in children, including balance, sprinting, jumping and side stepping. Toe flexor strength (TFS) is recommended as part of the clinical assessment of foot function in children. Fixed dynamometry, rather than handheld, is the gold standard of measurement; however, it can be prohibitively costly. No fixed dynamometer reliability studies on toe flexion have been conducted in children to date. Research questions: Does the novel fixed hand-held dynamometer (HHD) protocol provide reliable intra-rater and test-retest measurements of toe flexor strength in children aged 10 to 12? Methods: Two trials were recorded from 14 healthy children (10?12 years), 7?14 days apart by the same rater. A Lafayette HHD (model 01163) measured peak force. The HHD was secured in a mobile custom mould below a step with a strap, which secured the foot of the participant. The receptor pads of the HHD were level with the upper surface of the step, maintaining neutral toe joints at rest. The participant was seated on an adjustable stool to ensure the hip, knee and ankle were each at 90? flexion, with the testing foot flat on the upper surface of the step. The averages of three maximal five second efforts were used for data analysis using a two-way mixed effects model with repeated measures ANOVA (intraclass correlation coefficient ICC 3,3). Standard error of measurement (SEM) was calculated to determine the absolute between trial variability. Results: The novel fixed HHD protocol provided excellent test-retest reliability with small measurement error for hallux (ICC 3,3 = 0.93, 95 % CI 0.78-0.98, SEM = 4.31 N) and lesser toe flexor strength testing (ICC 3,3 = 0.96, 95 % CI 0.87-0.99, SEM = 1.86 N). Significance: The fixed HHD protocol described in this study has excellent reliability for the test-retest evaluation of children?s toe flexor strength.

Cholesteryl ester transfer protein (CETP) represents one of the key regulators of the homeostasis of lipid particles, including high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles. Epidemiological evidence correlates increased HDL and decreased LDL to coronary heart disease (CHD) risk reduction. This relationship is consistent with a clinical outcomes trial of a CETP inhibitor (anacetrapib) combined with standard of care (statin), which led to a 9% additional risk reduction compared to standard of care alone. We discuss here the discovery of MK-8262, a CETP inhibitor with the potential for being the best-in-class molecule. Novel in vitro and in vivo paradigms were integrated to drug discovery to guide optimization informed by a critical understanding of key clinical adverse effect profiles. We present preclinical and clinical evidence of MK-8262 safety and efficacy by means of HDL increase and LDL reduction as biomarkers for reduced CHD risk.

Background: Poor postural balance in the upright position is strongly correlated to morbidities, such as falls in older adult populations and to lower limb injuries in the younger populations. Good postural balance depends on muscular strength and the integration of neurological and muscular feedback mechanisms throughout the body. Since the interface with the ground is the plantar surface of each foot, an improved understanding of the role of foot muscles in postural balance is warranted. Research question: Does improved toe flexor strength result in better postural balance, across the lifespan? Methods: A systematic review was conducted of papers from 1900 to 2019 inclusive, from five databases. Inclusion and exclusion criteria were established prior to selection. Inclusion criteria were: observational and longitudinal studies, healthy subjects, at least one balance and one toe flexor strength test conducted. Exclusion criteria were: subjects with a pathology/disability, case study, systematic or literature review. Two examiners assessed a study's suitability for inclusion in this review, based on the above criteria. Study quality was assessed using the Critical Appraisal Skills Program Tools. The type of studies and methodological heterogeneity precluded the feasibility of conducting a meta-analysis. Results: Nine studies were included. In each study, participants were over sixty years of age, and over 73 % of them were female. No study was found for a younger population group. There were seven cross-sectional studies, two randomized control trials and there was one case-control study. All studies provided evidence of directly proportional, clinically significant correlations between toe flexor strength and postural balance. Significance: Toe flexor strength contributes to improved postural balance for people over the age of 60. Research is needed to establish the relationship between foot muscle strength and balance in younger adults and children.

Dry-land strength training is a common component of swimming programs; however, its efficacy is contentious. A common criticism of dry-land strength training for swimming is a lack of specificity. An understanding of movement patterns in swimming can enable dry-land strength training programs to be developed to elicit adaptations that transfer to improvements in swimming performance. This study aimed to quantify the range and velocity of hip roll, shoulder roll, and torso twist (produced by differences in the relative angle between shoulder roll and hip roll) in front crawl at different swimming speeds. Longitudinal torso kinematics was compared between sprint and 400-m pace front crawl using 3D kinematics of 13 elite Scottish front crawl specialists. The range (sprint: 78.1 degrees; 400 m: 61.3 degrees) and velocity of torso twist (sprint: 166.3 degrees.s(-1); 400 m: 96.9 degrees.s(-1)) were greater at sprint than 400-m pace. These differences were attributed to reductions in hip roll (sprint: 36.8 degrees; 400 m: 49.9 degrees) without corresponding reductions in shoulder roll (sprint: 97.7 degrees; 400 m: 101.6 degrees) when subjects swam faster. Shoulder roll velocity (sprint: 190.9 degrees.s(-1); 400 m: 139.2 degrees.s(-1)) and hip roll velocity (sprint: 75.5 degrees.s(-1); 400 m: 69.1 degrees.s(-1)) were greater at sprint than 400-m pace due to a higher stroke frequency at sprint pace (sprint: 0.95 strokes.s(-1); 400 m: 0.70 strokes.s(-1)). These findings imply that torques acting to rotate the upper torso and the lower torso are greater at sprint than 400-m pace. Dry-land strength training specificity can be improved by designing exercises that challenge the torso muscles to reproduce the torques required to generate the longitudinal kinematics in front crawl.

Knowledge of the kinematic differences that separate highly skilled and less-skilled squash players could assist the progression of talent development. This study compared trunk, upper-limb and racket kinematics between two groups of nine highly skilled and less-skilled male athletes for forehand drive, volley and drop strokes. A 15-camera motion analysis system recorded three-dimensional trajectories, with five shots analysed per participant per stroke. The highly skilled group had significantly (p< 0.05) larger forearm pronation/supination range-of-motion and wrist extension angles at impact than the less-skilled. The less-skilled group had a significantly more "open" racket face and slower racket velocities at impact than the highly skilled. Rates of shoulder internal rotation, forearm pronation, elbow extension and wrist flexion at impact were greater in the drive stroke than in the other strokes. The position of the racket at impact in the volley was significantly more anterior to the shoulder than in the other strokes, with a smaller trunk rotation angular velocity. Players used less shoulder internal/external rotation, forearm pronation/supination, elbow and wrist flexion/extension ranges-of-motions and angular velocities at impact in the drop stroke than in the other strokes. These findings provide useful insights into the technical differences that separate highly skilled from less-skilled players and provide a kinematic distinction between stroke types.

To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball's velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a "zeroing-in" effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the "functionality" of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot.

In recent years, wearable exoskeletons and powered prosthetics have been considered key elements to remedy mobility loss. One of the main challenges pertaining to this field is the prediction of the wearer's desired motion. In this paper, we perform a human locomotion analysis, and we investigate the accuracy of predicting the angular position of the lower limb joints from the motion of walking canes. Nine healthy subjects took part of this study and performed a locomotor task that comprised straight walking on flat ground, stair ascent, and upright resting posture. Recurrent Neural Networks and polynomial fitting using Least Squares were used to model dynamic and static non-linear mappings, respectively, between the motion of a cane and its contra-lateral leg joints. A successful prediction of both the hip and knee joints was achieved using information from the cane only, and significant improvement of the prediction error was realized through the addition of data from the arm joints. Overall, Recurrent Neural Networks outperformed Least Squares for both joints' angular position prediction. When using the cane only, the static maps were able to predict steady behaviour but failed in predicting transitioning, as opposed to RNN, which was able to capture both steady behaviour and transitions.

Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0-90 degrees, with static data collected at 10 degrees increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE <= 0.03 degrees). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50 degrees and ICC showed very high correlations (r >= 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were <= 2.20 degrees. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics.

Objectives: To investigate the association between air jacket usage and rider injury severity in equestrian eventing competition falls world-wide. Design: Retrospective data analysis. Methods: An analysis was conducted on Federation Equestre Internationale data for 1819 riders who fell wearing an air jacket and 1486 riders who fell while not wearing an air jacket from 2015 to 2017. Injury data were categorised as either 'no/slight injury' or 'serious/fatal injury'. A chi-square test determined whether an association was present between injury severity category and air jacket usage and binary logistic regression determined the effect size of this association. Results: As a result of falls, 3203 riders sustained no/slight injuries and 102 sustained serious/fatal injuries. While 55.0% of riders who fell were wearing an air jacket, they represented 67.6% of the serious/fatal injury outcomes. Air jacket usage was significantly associated with serious/fatal injuries in falls (X-2 =6.76; p = 0.009). Riders wearing an air jacket had 1.7 times (95%CI 1.14-2.64) increased odds of sustaining a serious or fatal injury in a fall compared to riders not wearing an air jacket. Conclusions: Riders wearing an air jacket were over represented in the percentage of serious or fatal injuries in falls compared to riders who only wore a standard body protector. Further research is needed to understand the reason(s) for this finding. It is recommended that additional data on injury outcomes, rider characteristics and the biomechanics of falls be examined in future analyses, and that air jacket and body protector characteristics be further investigated. (C) 2019 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Amputation is the major cause of gait impairment in our society and is due to several factors and conditions such as war injuries or diabetes lower limb complication, often resulting in a gait impairment. Active prosthetics have been considered to remedy this mobility loss. These devices have the potential to enhance significantly the quality of life of patients. One major challenge resides in the generation of smooth trajectories, especially during gait transitioning for the active joints of the powered devices. Here we propose a smooth trajectory predictor for above-knee prosthetics, where the motion of the hip joints is translated into knee and ankle joint trajectories. We consider a locomotion task that includes overground walking and stairs ascent. Successful prediction is achieved for both knee and ankle joint angular positions.