RE-EVALUATING WHAT WE “KNOW” ABOUT FEMALE ATHLETES IN BIOMECHANICS RESEARCH: ACROSS THE CONTINUUM FROM CAPACITY TO SKILL

Data from recent research around gender bias as a result of lack of control for physical capacity measures or skill assessment. Research data and case studies will be used to determine if we really “know” what we’ve said about the biomechanics of female athletes and what we might consider when putting forward recommendations based on these conclusions. The overall premise will be to remind ourselves as sports biomechanists that although we should have an expertise, we need to also be an excellent generalist to do our job well, especially in the applied environment where we see bias on both ends of the spectrum from “capacity” focused to “performance” focused research. Examples of going from biomechanics to S&C will be provided as well as a justification why our biomechanics research needs to extend athlete characteristics beyond just “gender, height, weight and age”

Biological system energy algorithm reflected in sub-system joint work distribution movement strategies: influence of strength and eccentric loading

© 2020, The Author(s). To better understand and define energy algorithms during physical activity as it relates to strength and movement strategy of the hip, knee and ankle, a model of increasing eccentric load was implemented in the current investigation utilizing a countermovement jump and a series of drop jumps from different heights (15, 30, 45, 60, 75 cm). Twenty-one participants were grouped by sex (men, n = 9; women, n = 12) and muscle strength (higher strength, n = 7; moderate strength, n = 7; lower strength, n = 7) as determined by a maximal squat test. Force plates and 3D motion capture were utilized to calculate work for the center of mass (COM) of the whole body and individually for the hip, knee and ankle joints. Statistically significant lower net work of the COM was observed in women and lower strength participants in comparison to men and moderate strength and higher strength participants respectively (p ≤ 0.05). This was primarily due to higher negative to positive work ratios of the COM in women and lower strength participants during all jumps. Furthermore, the COM negative work was primarily dissipated at the knee joint in women and in the lower strength group, particularly during the higher drop jump trials, which are representative of a demanding eccentric load task. A definitive energy algorithm was observed as a reflection of altering joint work strategy in women and lower strength individuals, indicating a possible role in knee joint injury and modulation of such by altering muscular strength

When task constraints delimit movement strategy: Implications for isolated joint training in dancers

Athletic performance is determined by numerous variables that cannot always be controlled or modified. Due to aesthetic requirements during sports such as dance, body alignment constrains possible movement solutions. Increased power transference around the ankle-joint, coupled with lower hip-joint power, has become a preferential strategy in dancers during leaps and may be considered a dance-specific stretch-shortening cycle (SSC) demand. Newell\u27s theoretical model of interacting constraints includes organismic (or individual), environmental, and task constraints describing the different endogenous and exogenous constraints individuals must overcome for movement and athletic performance. The unique task constraints imposed during dance will be used as a model to justify an isolated joint, single-targeted block progression training to improve physical capacity within the context of motor behavior to enhance dance-specific SSC performance. The suggested ankle-specific block progression consists of isometrics, dynamic constant external resistance, accentuated eccentrics, and plyometrics. Such programming tactics intend to collectively induce tendon remodeling, muscle hypertrophy, greater maximal strength, improved rate of force development, increased motor unit firing rates, and enhanced dynamic movement performance. The current perspective provides a dualistic approach and justification (physiological and motor behavioral) for specific strength and conditioning programming strategies. We propose implementation of a single-targeted block progression program, inspired by Newell\u27s theoretical model of interacting constraints, may elicit positive training adaptations in a directed manner in this population. The application of Newell\u27s theoretical model in the context of a strength and conditioning supports development of musculoskeletal properties and control and is conceptually applicable to a range of athletes

Isolated joint block progression training improves leaping performance in dancers

The purpose of this study was to investigate the effect of a 12-week ankle-specific block progression training program on saut de chat leaping performance [leap height, peak power (PP), joint kinetics and kinematics], maximal voluntary isometric plantar flexion (MVIP) strength, and Achilles tendon (AT) stiffness. Dancers (training group n = 7, control group n = 7) performed MVIP at plantarflexed (10◦) and neutral ankle positions (0◦) followed by ramping isometric contractions equipped with ultrasound to assess strength and AT stiffness, respectively. Dancers also performed saut de chat leaps surrounded by 3-D motion capture atop force platforms to determine center of mass and joint kinematics and kinetics. The training group then followed a 12-week ankle-focused program including isometric, dynamic constant external resistance, accentuated eccentric loading, and plyometric training modalities, while the control group continued dancing normally. We found that the training group\u27s saut de chat ankle PP (59.8%), braking ankle stiffness (69.6%), center of mass PP (11.4%), and leap height (12.1%) significantly increased following training. We further found that the training group\u27s MVIP significantly increased at 10◦ (17.0%) and 0◦ (12.2%) along with AT stiffness (29.6%), while aesthetic leaping measures were unchanged (peak split angle, mean trunk angle, trunk angle range). Ankle-specific block progression training appears to benefit saut de chat leaping performance, PP output, ankle-joint kinetics, maximal strength, and AT stiffness, while not affecting kinematic aesthetic measures. We speculate that the combined training blocks elicited physiological changes and enhanced neuromuscular synchronization for increased saut de chat leaping performance in this cohort of dancers

Training for “worst-case” scenarios in sidestepping: Unifying strength and conditioning and perception–action approaches

Sidesteps can impose high demands on the knee joint and lead to non-contact anterior cruciate ligament (ACL) injuries. Understanding how different constraints shape an athlete’s movement strategy and the associated joint demands can help design training interventions to increase injury resilience. Motor capacities, such as muscular strength and power, act as boundaries for the safe execution of perceptual–motor skills and co-determine the emergence of unique movement strategies. Increasing single- and multi-joint strength enables a broader solution space for movement strategies and increases load tolerance. Manipulating task constraints during sidesteps can be used in the training process to systematically expose athletes to increasing demands (on the knee joint or any joint or structure) in preparation for “worst-case” scenarios. In particular, the type and timing of information available influence the preparation time, subsequently affecting the movement strategy and the associated magnitude of external knee joint loading (e.g., knee valgus moment). While an athlete’s perceptual–cognitive skills contribute to the preparation time during in situ scenarios, attempts to further improve those skills with the aim of increasing athlete preparation time prior to “worst-case” scenarios are yet to demonstrate conclusive evidence of transfer to on-field situations. Therefore, in the current article, we reflect on the impact of different interacting constraints that influence the execution of sidesteps during in situ scenarios and impose high demands on the knee joint. Subsequently, we discuss how an integrated perspective, drawing on knowledge and perspectives from strength and conditioning and perception–action, may enhance an athlete’s ability to withstand “worst-case” scenarios and adapt to perform varied movement executions when sidestepping

With great power comes great responsibility: Common errors in meta-analyses and meta-regressions in strength & conditioning research

Background and Objective: Meta-analysis and meta-regression are often highly cited and may influence practice. Unfortunately, statistical errors in meta-analyses are widespread and can lead to flawed conclusions. The purpose of this article was to review common statistical errors in meta-analyses and to document their frequency in highly cited meta-analyses from strength and conditioning research. Methods: We identified five errors in one highly cited meta-regression from strength and conditioning research: implausible outliers; overestimated effect sizes that arise from confusing standard deviation with standard error; failure to account for correlated observations; failure to account for within-study variance; and a focus on within-group rather than between-group results. We then quantified the frequency of these errors in 20 of the most highly cited meta-analyses in the field of strength and conditioning research from the past 20 years. Results: We found that 85 % of the 20 most highly cited meta-analyses in strength and conditioning research contained statistical errors. Almost half (45 %) contained at least one effect size that was mistakenly calculated using standard error rather than standard deviation. In several cases, this resulted in obviously wrong effect sizes, for example, effect sizes of 11 or 14 standard deviations. Additionally, 45 % failed to account for correlated observations despite including numerous effect sizes from the same study and often from the same group within the same study. Conclusions: Statistical errors in meta-analysis and meta-regression are common in strength and conditioning research. We highlight five errors that authors, editors, and readers should check for when preparing or critically reviewing meta-analyses

Braking ground reaction force during 90deg sidestep cut and leg muscle strength.

Change of direction (COD) total time is influenced by linear sprint ability and technique. Therefore, COD performance should be isolated from COD total time by measuring only the time taken to perform the COD and COD technique should be controlled. Current COD studies focus on the plant and penultimate (PEN) braking steps (Dos’ Santos et al, 2017, Jones et al, 2017), however, deceleration during a COD extends beyond these two steps (Nedergaard et al, 2014), thus, more braking steps ground reaction forces (GRF) needs to be examined. Cross sectional COD studies have shown that athletes with faster COD performance were stronger during eccentric squat (Spiteri et al, 2015) and produced higher force during eccentric isokinetic knee extensor and flexor test than athletes who exhibit slower COD performance (Jones et al, 2017). Therefore, it seems that eccentric strength is associated with COD performance. It is necessary to examine braking steps before the PEN step to examine braking strategies of faster and slower performers. Additionally, eccentric strength, which is deemed advantageous for COD braking should be further examined using a multi-joint strength assessment to further determine eccentric capacity during COD performance.https://ro.ecu.edu.au/ecuposters/1027/thumbnail.jp

EFFECTS OF TASK CONSTRAINTS ON SIDESTEPPING JOINT KINETICS

The purpose of this study was to assess the change in lower limb joint kinetics associated with anterior cruciate ligament injury (ACL) risk in sidesteps with and without task constraints. Female athletes (n=21) performed pre-planned and unplanned sidesteps with and without task constraints to the trunk and the preparatory step. Statistical differences in negative peak joint power for the hip, knee and ankle during the execution step, the entry velocity and the sidestep angle between the constrained and unconstrained sidesteps were determined with a linear mixed model. The entry velocity decreased for all unplanned sidesteps compared to pre-planned sidesteps. Trunk constraints increased knee joint loading in pre-planned sidesteps (-24.51 ± 11.27 W·kg-1) compared to unconstrained unplanned sidesteps (-17.69 ± 8.58 W·kg-1). Understanding how constraints can alter the magnitude of lower-body joint loading can help design effective drills to overload single-joint capacities