This study analyses the clubhead trajectory characteristics of driver swings, with a specific focus on the delivery plane. This swing segment extends from the point where the club shaft is parallel to the ground during the downswing to the corresponding parallel position post-impact. To differentiate skill-level characteristics, data obtained from 127 swing captures, including world-class golf players, were categorised into three skill-level groups and were geometrically analysed. The clubhead trajectories were fitted to a planar ellipse, extending previous analysis from the first half to the entire delivery plane. Methodologically, differential geometry is used to compute the trajectory’s curvature evolution. The statistical analysis of the key variables across groups confirms a significant correlation between the clubhead trajectory and the skill level. High-performance players presented a distinct club movement pattern, characterised by a specific curvature pattern that supplements planarity as a skill-level predictor during the delivery plane. Specifically, high-skilled players showed smaller ellipses with reduced radii of curvature, and less flattening than the less-skilled golfers. The results provide a quantitative framework with direct implications for swing modelling, equipment testing and design, and swing biomechanics evaluation.
Perforation geometry may influence pickleball flight, but repeated-launch evidence remains limited. We compared an author-designed and manufactured 36-hole outdoor prototype with an author-manufactured 40-hole reference based on the geometry commonly used for commercial outdoor balls. Thirty balls per design were launched over four loading cycles, giving 120 launches per design. Landing positions were digitised from high-speed video and analysed using coordinate dispersion, distance from the design-specific centroid and 95
This study investigated the influence of force-application misalignments on measurements of rolling resistance in wheels using the force method. A theoretical model was developed to predict measurement errors caused by angular deviations between the load-cell axis and the normal direction of the rolling surface, as well as by horizontal axle offset during measurements on a cylindrical surface. The model was experimentally evaluated by measuring the rolling resistance coefficient of roller-ski wheels on both a flat treadmill rolling surface and a cylindrical rolling surface. The results demonstrated that force-based rolling-resistance measurements are sensitive to small geometric misalignments. Angular deviations affected measurements on both flat and cylindrical rolling surfaces, whereas horizontal axle offset affected measurements on the cylindrical rolling surface. The experimentally measured rolling-resistance coefficients showed good agreement with the corresponding values predicted by the theoretical model across all tested conditions. This indicates that the model adequately captures the dominant effects of applied-force misalignment on measurement errors. The findings highlight the importance of accurate force-transducer alignment and wheel positioning in rolling-resistance measurements when using the force method. Overall, the proposed theoretical model provides a practical tool for predicting and correcting alignment-induced measurement errors in laboratory-based rolling-resistance testing.
Short-track speed skating involves high biomechanical demands due to repeated transitions between straights and curves. While plantar pressure insoles provide a non-intrusive method to assess loading patterns, their repeatability under real short-track speed skating conditions remain poorly documented. Ten competitive short-track speed skating athletes (5 women and 5 men; age: 18.8 ± 1.2 years; height: 171.2 ± 10.6 cm; mass: 68.8 ± 7.2 kg) performed repeated on-ice trials while equipped with pressure insoles and triaxial accelerometers, with a wearable camera for reference. A pressure-based algorithm automatically segmented half-laps. Intra-session repeatability of plantar pressure, center-of-pressure position, and acceleration signals was assessed using intraclass correlation coefficients, standard error of measurement, and statistical parametric mapping repeated-measures analysis of variance. Within- and between-trial variability was additionally quantified using the root mean square error. No significant trial effects were found, indicating consistent movement patterns across trials. Plantar pressure and center-of-pressure measurements demonstrated fair-to-excellent repeatability (intraclass correlation coefficients greater than 0.70 for mediolateral center-of-pressure), whereas acceleration measurements showed poor repeatability (intraclass correlation coefficient below 0.30). Across all variables, between-trial root mean square error values were lower than within-trial root mean square error values, suggesting that removing and repositioning the insoles did not substantially increase measurement variability. These findings support the repeatability of plantar pressure and center-of-pressure measurements obtained with pressure insoles under real on-ice short-track speed skating conditions.
This study analysed the frequency domain characteristics of acceleration data from upper-body mounted inertial measurement units across a controlled and game environment. Understanding the frequency content of such data can inform the selection of sampling frequencies for wearable athlete tracking systems. Two cohorts were used for this study (I) thirteen competitive male and female athletes who completed a circuit representative of common team sport movements with data collected using a research-grade inertial measurement unit sampling at 1136 Hz; and (II) Game data of twenty-three elite male Australian Football athletes collected using a Global Navigation Satellite System-embedded inertial measurement unit sampling at 100 Hz during one full match. Two spectral metrics were derived from one-sided power density estimates: the dominant movement frequency (frequency at peak power), and the upper limit frequency at half peak power. In the controlled environment, dominant frequencies ranged from < 1.6 Hz (jump and zigzag) to 6.2 Hz for backwards running. The dominant movement frequency in the game environment was 2.8 Hz (peak power: 11 (m/s²)²/Hz), comparable to the dominant movement frequency across all controlled environment movements combined (2.8 Hz; peak power: 8.6 (m/s²)²/Hz). These findings provide preliminary evidence that the most relevant frequency content of upper-body mounted inertial measurement unit acceleration signals during team sport movements is concentrated below approximately 5 Hz. The frequency-domain reference established in this study provides a conservative estimate of the sampling requirements for monitoring whole-body athlete movement. The findings may assist practitioners and researchers in interpreting the capabilities and limitations of wearable athlete tracking systems they utilise. However, further validation across diverse sports, devices, competitive levels, and game contexts is required before firm technical guidelines can be established.
