Marcus Dunn

With continued advancement in flooring technology, modular sports flooring tiles have emerged as a potential alternative flooring solution for sports performance. However, there is limited empirical evidence regarding their effects on ground reaction forces in landing tasks (GRFs). Therefore, the aim of this study was to assess the effects of flooring surface on peak GRFs during bilateral drop landings. Eighteen physically active adults (10 males, 8 females) completed three bilateral drop landings from a 50 cm height across each of three flooring types: modular sport tiles, athletic track, and bare force plates, measuring contacts from both the left and right limb. GRFs were captured using two in-ground force platforms, normalised to body mass, and then analysed using a linear mixed-effects model with post-hoc comparisons where significant interactions were recorded. Peak anterior GRFs were significantly lower in the modular tiles compared with athletic sports track and bare metal surfaces (p < 0.001, η²_p ≥ 0.430). Additionally, anterior (p = 0.048, η²_p = 0.040), lateral (p < 0.001, η²_p = 0.280), and vertical (p = 0.001, η²_p = 0.100) GRFs were significantly greater in the right limb compared with the left limb within each flooring surface condition. Future research should investigate sport-specific movement patterns and long-term adaptations associated with training on modular surfaces to assess their potential role in enhancing performance and mitigating injuries.

The purpose of this study was to determine the number of crank revolutions required to obtain stable mean values of sagittal plane biomechanics variables, and the between-session reliability of these variables, whilst cyclists used an aerodynamic position. Eighteen elite cyclists completed a 3-min maximal bout on a cycling ergometer. Lower-limb kinematic and kinetic data were captured using 2D motion capture and force pedals. Raw data were filtered using a 4th order Butterworth low-pass filter (6 hz) and interpolated to 100 points per revolution. The middle 60 revolutions of each trial were extracted and 37 discrete and 15 time-series variables were calculated. Mean stability was assessed in all participants, and between-session reliability was analysed in a subset of 11 participants. Sequential averaging indicated more revolutions to stability than iterative intra-class correlation coefficients. Crank kinetics were more stable than joint kinematics and kinetics. For stable discrete and time-series variables, 30 and 38 revolutions are recommended, respectively. Between-day reliability for all variables was moderate to excellent, and good to excellent for crank kinetics and joint kinematics variables. Hip flexion-extension and ankle dorsiflexion kinetics were least reliable. Researchers and applied practitioners should consider these findings when planning, and interpreting results from, cycling biomechanics interventions.

The purpose of this study was to explore the experiential knowledge of tennis coaches as it related to the development of grip positions in tennis athletes. Accredited tennis coaches (n = 11) completed semi-structured interviews consisting of open-ended questions about their coaching background, the importance of grip positions compared with other areas of foundational development, and their opinions on using physically-constraining tools (PCTs). Two major themes, “Grip positions are an adaptive skill” and “Why and how do I modify an athlete’s grip?”, were identified. Coaches expressed the opinion that grip positions were dynamic and a modifiable component of tennis stroke technique. Irrespective of shot type, grip positions were viewed as a non-negotiable aspect of talent development and intrinsically linked to other components of the stroke. Coaches questioned the necessity of technique refinement for grip positions given the complex and time-costly nature of bringing about effective motor-behaviour change. Some coaches expressed reservations about skill transfer into live match-play, intuitively expressing the concepts of the constraints-led approach to manipulate key variables within the athlete’s environment to foster learning. Future research should aim to assess the short- and long-term effects of PCT use in tennis and establish the extent to which PCTs can impact learning and skill transfer.

This study aimed to understand how tennis coaches perceive and approach the development of grip positions, a foundational skill in tennis. Professionally accredited coaches, classed as less (n = 140) or more (n = 86) experienced, participated in an online survey where they provided their perspectives on the importance of developing grip positions and their opinions on using physically constraining tools for coaching. Irrespective of coach experience level, the findings revealed that technique development and grip position training were ranked as the two most important components in foundational tennis skill development. The Semi-western grip for forehand (less: 68%; more: 65%), a combination of Continental and Eastern grips for double-handed backhand (less: 59%; more: 48.8%), and the Continental grip for serves (both: 94%) were identified as the most commonly taught positions for different shots. Perceived barriers to developing grip positions were out of habit (less: 62%; more: 56%), discomfort (less: 58%; more: 50%), and lack of confidence (less: 44%; more: 21%). Notably, 65% of coaches expressed an openness to incorporating physically constraining tools to enhance grip-specific skill development. Overall, this study serves as a foundational resource, guiding coaches in optimising their strategies for foundational tennis development, prompting further research in this area.

In clinic settings, factors such as time, cost, expertise, and technology feasibility limit the use of instrumented biomechanical analysis. Recent advances in commercial markerless motion capture systems can address patient ease-of-use factors, but are high cost and require specialised equipment, dedicated spaces, and technical expertise. As such, they present similar limitations to biomechanical analyses in clinic settings. Single-camera pose estimation techniques have generated cautious optimism for markerless gait analysis. However, parameters derived using low-cost and low-sample rate cameras commonly used in clinic settings are not yet accurate enough to detect change in complex movement systems. Video frame interpolation is a single-step process that artificially increases the sample rate of videos. This study applied video frame interpolation to videos of walking and demonstrates improved precision for step, stance, swing and double support times, as well as marginal improvements to the precision of ankle and knee joint angles, derived by single-camera pose estimation. Video frame interpolation potentially represents a delimiting factor for gait analysis in clinic settings, as limiting factors such as time, cost, technology feasibility and patient ease-of-use can be minimised.

The visco-elastic properties of a football influence how it bounces and therefore its performance in a game. Previously, high-speed camera footage has been used to quantify deformation, coefficient of restitution and contact time for an impact between a football and a rigid surface but these systems do not provide any information on the forces acting on the football during the impact. The aim of this study was to determine the repeatability of measuring the peak impact force, impulse, rise time and loading rate for four samples of the same model of football using a commercial force platform (Kistler 9281EA). A football impacted the floor-mounted piezoelectric-type force platform at 6.04 and 19.4 m s⁻¹. High absolute (coefficient of variation (CV) ≤ 10%) and relative (intraclass correlation coefficient (ICC) ≥ 0.94) repeatability was observed for repeated impacts at both velocities. The minimal detectable differences were calculated to evaluate the ability for the force platform to be used to make meaningful comparisons between footballs. For all metrics, the minimum detectable difference accounted for less than 5% of the mean value. Therefore, it can be concluded that provided the difference in impact metrics between football models exceeds the minimal detectable difference, the commercial force platform can be used to measure and detect differences in physical impact metrics between models of footballs.

By Katie Mills, Johsan Billingham, Simon Choppin, et al., Published on 06/06/22

Athletes use either an eight-step or a seven-step strategy to reach the first hurdle in the 110 m hurdles event. This study investigates the effect of step strategy on the hurdle clearance technique and spatio-temporal parameters of the four steps prior to hurdle clearance. Two-dimensional video data were collected in the sagittal plane from 12 male sprinters, grouped as seven-step (n = 6) or eight-step (n = 6) strategists. The take-off distance was 0.20 m further from the hurdle and the touchdown was 0.42 m closer to the hurdle for seven-step athletes. Additionally, seven-step athletes reduced the length of the final step before hurdle take-off by 0.14 m compared with the previous step, whereas the eight-step athletes extended their final step by 0.17 m. There was negligible difference between the mean horizontal velocities of the two groups throughout the hurdle clearance (0.02 m/s) or the approach time to the first hurdle from the block clearance (0.01 s). This presents an important first insight into the effect of the step strategy on the first hurdle kinematics. Our findings identify the take-off and touchdown distance parameters of the hurdle clearance technique, and approach step characteristics for a successful seven- or eight-step approach strategy to be employed.

Athletes use either a seven-step or eight-step strategy to reach the first hurdle in the 110 m hurdle event. This study investigated the effect of step strategy on the start position, the block exit and the first four approach steps. Two-dimensional video data were collected in the sagittal plane from 12 male sprinters, grouped as seven-step (n = 6) or eight-step (n = 6) strategists. Mean block spacing was 0.08 m further apart, block contact time 0.06s longer, first step 0.25 m longer and first ground contact 0.03s longer for seven-step athletes compared with eight-step athletes. There was also a greater vertical displacement of the centre of mass (CoM) (0.04 m) for the seven-step athletes compared with the eight-step athletes. Additionally, the front hip mean angular acceleration was 197°/s² slower for the seven-step athletes than the eight-step athletes. There was limited difference between groups for mean horizontal velocity at the moment of block exit (0.14 m/s). These technical alterations provide an important first insight into start kinematics. The findings of this study identify the position in the starting blocks, and the key parameters which pertain to the initial phases for a successful seven-step approach strategy to be employed.