Dr Stuart McErlain-Naylor is a Lecturer in Sport and Exercise Biomechanics at Loughborough University, UK. He is currently Vice President (Publications) of the International Society of Biomechanics in Sports.
Alongside a passion for engaging the wider audience in all things sports biomechanics, Stuart’s research interests include the application of wearable technology and computer simulation methods to investigate the human body’s response to sporting impacts.
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PhD in Sports Biomechanics, 2018
Postgraduate Certificate in Academic Practice (Fellow of the Higher Education Academy), 2020
University of Suffolk
BSc in Sport and Exercise Sciences, 2013
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Applying wearable technology and computer simulation to investigate the body’s response to sporting impacts
Organismic, task, and environmental constraints are known to differ between skilled male and female cricket batters during power hitting tasks. Despite these influences, the techniques used in such tasks have only been investigated in male cricket batters. This study compared power hitting kinematics between 15 male and 15 female batters ranging from university to international standard. General linear models were used to assess the effect of gender on kinematic parameters describing technique, with height and body mass as covariates. Male batters generated greater maximum bat speeds, ball launch speeds, and ball carry distances than female batters on average. Male batters had greater pelvis-thorax separation in the transverse plane at the commencement of the downswing (β = 1.14; p = 0.030) and extended their lead elbows more during the downswing (β = 1.28; p = 0.008) compared to female batters. The hypothesised effect of gender on the magnitude of wrist uncocking during the downswing was not observed (β = −0.14; p = 0.819). The causes of these differences are likely to be multi-factorial, involving aspects relating to the individual players, their history of training experiences and coaching practices, and the task of power hitting in male or female cricket.
The identification of optimum technique for maximal effort sporting tasks is one of the greatest challenges within sports biomechanics. A theoretical approach using forward-dynamics simulation allows individual parameters to be systematically perturbed independently of potentially confounding variables. Each study typically follows a four-stage process of model construction, parameter determination, model evaluation, and model optimization. This review critically evaluates forward-dynamics simulation models of maximal effort sporting movements using a dynamical systems theory framework. Organismic, environmental, and task constraints applied within such models are critically evaluated, and recommendations are made regarding future directions and best practices. The incorporation of self-organizational processes representing movement variability and “intrinsic dynamics” remains limited. In the future, forward-dynamics simulation models predicting individual-specific optimal techniques of sporting movements may be used as indicative rather than prescriptive tools within a coaching framework to aid applied practice and understanding, although researchers and practitioners should continue to consider concerns resulting from dynamical systems theory regarding the complexity of models and particularly regarding self-organization processes.
The purpose of this study was to quantify the magnitude and frequency content of surface-measured accelerations at each major human body segment from foot to head during impact landings. Twelve males performed two single leg drop landings from each of 0.15 m, 0.30 m, and 0.45 m. Triaxial accelerometers (2000 Hz) were positioned over the: first metatarsophalangeal joint; distal anteromedial tibia; superior to the medial femoral condyle; L5 vertebra; and C6 vertebra. Analysis of acceleration signal power spectral densities revealed two distinct components, 2-14 Hz and 14-58 Hz, which were assumed to correspond to time domain signal joint rotations and elastic wave tissue deformation, respectively. Between each accelerometer position from the metatarsophalangeal joint to the L5 vertebra, signals exhibited decreased peak acceleration, increased time to peak acceleration, and decreased power spectral density integral of both the 2-14 Hz and 14-58 Hz components, with no further attenuation beyond the L5 vertebra. This resulted in peak accelerations close to vital organs of less than 10% of those at the foot. Following landings from greater heights, peak accelerations measured distally were greater, as was attenuation prior to the L5 position. Active and passive mechanisms within the lower limb therefore contribute to progressive attenuation of accelerations, preventing excessive accelerations from reaching the torso and head, even when distal accelerations are large.
A logarithmic curve fitting methodology for the calculation of badminton racket-shuttlecock impact locations from three-dimensional motion capture data was presented and validated. Median absolute differences between calculated and measured impact locations were 3.6 [IQR: 4.4] and 3.5 [IQR: 3.5] mm mediolaterally and longitudinally on the racket face, respectively. Three-dimensional kinematic data of racket and shuttlecock were recorded for 2386 smashes performed by 65 international badminton players, with racket-shuttlecock impact location assessed against instantaneous post-impact shuttlecock speed and direction. Mediolateral and longitudinal impact locations explained 26.2% (quadratic regression; 95% credible interval: 23.1%, 29.2%; BF10 = 1.3 × 10131, extreme; p < 0.001) of the variation in participant-specific shuttlecock speed. A meaningful (BF10 = ∞, extreme; p < 0.001) linear relationship was observed between mediolateral impact location and shuttlecock horizontal direction relative to a line normal to the racket face at impact. Impact locations within one standard deviation of the pooled mean impact location predict reductions in post-impact shuttlecock speeds of up to 5.3% of the player’s maximal speed and deviations in the horizontal direction of up to 2.9° relative to a line normal to the racket face. These results highlight the margin for error available to elite badminton players during the smash.
This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump.
This study examined 503 power-hitting strokes that resulted in the maximum of 6-runs being scored in international men’s one-day and T20 cricket. Chi-Squared analyses were conducted to determine if performance and situational variables were associated with the distribution (direction) of aerial power-hitting strokes. Results revealed that bowling length, bowling line, bowler type and powerplays were all significantly (p < 0.001) associated with ball-hitting distribution. Post-hoc analysis of the standardised residuals revealed that greater than expected 6ʹs were scored behind square and were associated with short-pitched bowling, fast bowling and the power-play. Similarly, bowling the half-volley length and the outside off line resulted in greater than expected 6ʹs on the off-side. The results suggest that bowlers should try to avoid offering width outside the off stump as well as bowling the half-volley and short-pitched lengths as these bowling lines and lengths present batters with greater opportunities to score maximum runs. Fast bowling is revealed to be more susceptible to power-hitting strokes than spin bowling. Conversely, batters may wish to target the areas behind square or on the off-side for opportunities to score maximum runs, and they should look to take full advantage of the powerplay field restrictions.
The effect of load on time-series data has yet to be investigated during weightlifting derivatives. This study compared the effect of load on the force–time and velocity–time curves during the countermovement shrug (CMS). Twenty-nine males performed the CMS at relative loads of 40%, 60%, 80%, 100%, 120%, and 140% one repetition maximum (1RM) power clean (PC). A force plate measured the vertical ground reaction force (VGRF), which was used to calculate the barbell-lifter system velocity. Time-series data were normalized to 100% of the movement duration and assessed via statistical parametric mapping (SPM). SPM analysis showed greater negative velocity at heavier loads early in the unweighting phase (12–38% of the movement), and greater positive velocity at lower loads during the last 16% of the movement. Relative loads of 40% 1RM PC maximised propulsion velocity, whilst 140% 1RM maximized force. At higher loads, the braking and propulsive phases commence at an earlier percentage of the time-normalized movement, and the total absolute durations increase with load. It may be more appropriate to prescribe the CMS during a maximal strength mesocycle given the ability to use supramaximal loads. Future research should assess training at different loads on the effects of performance.
The purpose of this study was to determine if elite female cricket batters’ body or bat kinematics differed when facing fast or spin bowling in a power-hitting task. Six elite female cricket batters completed a straight drive power hitting task against both fast and spin bowling, captured by a 3D motion capture system. Select kinematic variables were analysed using Visual 3D software. Elite female batters may use the increased movement time afforded by the slower spin bowling speed to enhance bat-ball impact, bat speed and launch angle through reducing distance from the pitch of the ball to impact, and increasing thorax-pelvis separation (X-Factor) and top wrist ulnar deviation compared with facing fast bowling.
The aim of this research was to quantify the magnitude and timing of surface measured accelerations during the fast-bowling action. Eleven males performed 6 maximum velocity deliveries with accelerometers positioned over: both ankles; knees; hips; L5; L1; and the C7 vertebrae. Accelerometer signals exhibited decreased peak and increased time to peak acceleration from the ankle to the C7 sensor. Even when distal accelerations were largest at front foot contact, the body was still able to dissipate more than 90% of the acceleration. Active and passive mechanisms such as joint compliance and spinal compression within the body therefore likely contribute to the progressive attenuation of accelerations. The effects of such compliance on investigations of the intersegmental forces and moments during cricket fast-bowling via inverse dynamics warrants further investigation.
Accurate ball pitch length in cricket fast bowling is potentially achieved from a redundant combination of four ball release parameters. Yet, it is unknown how parameter co-variations affect pitch accuracy. This study investigates whether pitch length variance is determined by coordinated ball release parameter co-variability. Twelve fast bowlers performed 18 trials at a target length and ball kinematics were captured from an indoor 3D camera setup. Multi-linear regression analysis showed that the four release parameters accounted for 79% of pitch length variance, where vertical velocity variance accounted for the most variance. When each release parameter was independently shuffled across trials, a pitch length model showed no indication of coordinated co-variability between input parameters. Therefore, pitch length accuracy was achieved by independent control of vertical velocity.