Phillis Teng

This study investigated how midsole hardness of basketball footwear affects lower extremity biomechanics and impacts perception in drop vertical jumps. Eighteen male basketball players performed drop vertical jumps from three heights (31 cm, 46 cm, 61 cm) in basketball shoes of different midsole hardness (50, 60 Asker C). Biomechanical variables of the lower extremity and subjective perception were measured. This study found a significant drop height effect on the lower extremity biomechanics (p < 0.05), with greater ground reaction forces, joint kinetics, and prelanding muscle activation levels observed at higher drop heights. Basketball shoes with a softer midsole led to higher forefoot peak force (p = 0.028) amid lower rearfoot peak force (p = 0.046), lower peak flexion moments at the ankle (p = 0.024) and hip joints (p = 0.029), and greater prelanding muscle activation in the rectus femoris (p = 0.042) and tibialis anterior (p = 0.043). It is concluded that changing midsole hardness within a commercially relevant range triggered a di erent prelanding muscle activation strategy and hence altered the magnitudes of ground reaction forces and joint loadings during landing. Subjectively, participants perceived higher landing impacts with greater drop heights, though the strength of the associations were weak.

This study investigated the between-limb asymmetry in kinetic and temporal characteristics during bilateral plyometric drop jumps from different heights. Seventeen male basketball players performed drop jumps from 3 heights on two platforms in randomized orders. Vertical ground reaction force data were analysed with respect to the lead limb (i.e. the limb stepping off the raised platform first) and trail limb. Peak forces and loading rates of each limb were calculated. The absolute time differential between the two limbs at initial ground contact and takeoff were determined. The frequency of symmetrical landing and taking off with “both limbs together” were counted using 3 time windows. Results showed that the lead limb displayed higher peak forces and loading rates than the trail limb across all heights (p <.05). As drop height increased, the absolute time differentials decreased at initial ground contact (p <.001) but increased at takeoff (p =.035). The greater the preset time window, the more landings and takeoffs were classified as bilaterally symmetrical. In conclusion, higher drop heights allowed subjects to become more bilaterally symmetrical in the timing of landing but this reduction in temporal asymmetry did not accompany with any reduction in kinetic asymmetry.

Increased knee flexion angles are associated with reduced non-contact anterior cruciate ligament (ACL) injury risks. Ankle plantar flexion angles and internal risk factors could influence knee flexion angles, but their correlations are unknown. This study aimed to establish and validate a regression model to predict knee flexion angles using ankle plantar flexion angles, body mass index (BMI) and generalised joint laxity (GJL) at initial contact of single-leg drop landings. Thirty-two participants performed single-leg drop landings from a 30-cm-high platform. Kinematics and vertical ground reaction forces were measured using a motion capture system and force plate. A multiple regression was performed, and it was validated using a separate data set. The prediction model explained 38% (adjusted R2) of the change in knee flexion angles at initial contact (p = 0.001, large effect size). However, only the ankle plantar flexion angle (p < 0.001) was found to be a significant predictor of knee flexion angles. External validation further showed that the model explained 26% of knee flexion angles (large effect size). The inverse relationship between ankle plantar flexion and knee flexion angles suggests that foot landing strategies could be used to increase knee flexion angles, thereby reducing non-contact ACL injury risks.

Purpose: Small knee flexion angles are associated with increased non-contact anterior cruciate ligament (ACL) injury risks. The purpose of this study was to provide insights into how ankle plantar flexion angles influenced knee flexion angles at initial contact during single-leg drop landings.

Method: Thirteen male recreational basketball players performed single-leg drop landings from a 30-cm high platform using three randomized foot-landing positions (natural, fore-foot, and flat-foot). A motion capture system and a force plate were used to measure lower extremity kinematics and vertical ground reaction force (VGRF). A one-way repeated measures Analysis of Variance and the Friedman test were conducted (α = .05).

Results: Foot-landing position had a significant effect on knee flexion angles at initial contact (p < .001). As compared to flat-foot landings (18° (SD 5°), significantly smaller knee flexion angles were found for natural (mean 12° (SD 5°), p = .004) and fore-foot landings (mean 12° (SD 3°), p = .001). There was however significantly smaller knee flexion range of motion in flat-foot landings (mean 42° (SD 3°), as compared to natural landings (mean 48° (SD 4°) (p < .001). Flat-foot landings also resulted in a 1.4 times higher maximum VGRF than fore-foot landings (p < .001) and 1.3 times higher than natural landings (p = .005).

Conclusions: Natural and fore-foot landings are better for force absorption but are associated with smaller knee flexion angles at initial contact. These findings have important implications for non-contact ACL injuries.

Gastrocnemius’ role as an agonist or antagonist of the anterior cruciate ligament (ACL) is not 27 well understood. This study explored the use of ultrasound imaging to investigate how 28 gastrocnemius stimulation levels influenced anterior tibial translation. The gastrocnemii of 10 29 participants were stimulated to four different levels using electrical muscle stimulation. The 30 quadriceps were co-activated at a fixed level. Anterior tibial translation was determined using 31 ultrasound imaging. Intraclass correlation coefficient [ICC (2,1)] was used to assess the intra-32 rater reliability over two sessions. Intra-rater reliability was good at rest and under most 33 muscle stimulation levels (ICC = 0.84 to 0.92), and moderate with the lowest (ICC = 0.71) 34 and highest stimulation (ICC = 0.61). While anterior tibial translation was not significantly 35 different across simulation levels, ultrasound imaging recorded the anterior movement of the 36 tibia as the gastrocnemius was activated, thus supporting gastrocnemius’ role as an antagonist 37 of the ACL.

In badminton, accurate service height detection is critical for ensuring fairness. We developed an automated service fault detection system that employed computer vision and machine learning, specifically utilizing the YOLOv5 object detection model. Comprising two cameras and a workstation, our system identifies elements, such as shuttlecocks, rackets, players, and players’ shoes. We developed an algorithm that can pinpoint the shuttlecock hitting event to capture its height information. To assess the accuracy of the new system, we benchmarked the results against a high sample-rate motion capture system and conducted a comparative analysis with eight human judges that used a fixed height service tool in a backhand low service situation. Our findings revealed a substantial enhancement in accuracy compared with human judgement; the system outperformed human judges by 3.5 times, achieving a 58% accuracy rate for detecting service heights between 1.150 and 1.155 m, as opposed to a 16% accuracy rate for humans. The system we have developed offers a highly reliable solution, substantially enhancing the consistency and accuracy of service judgement calls in badminton matches and ensuring fairness in the sport. The system’s development signifies a meaningful step towards leveraging technology for precision and integrity in sports officiation.

Ankle braces typically restrict the functional range of motion. Braces should preferably allow a free functional range of motion during sport while protecting the foot at high-risk positions beyond that range. This could be achieved with 3D printed metamaterial structures that could have varying properties throughout an individual’s ankle range of motion. This paper aims to illustrate an exploratory methodology of using an affordable Fused Deposition Modelling 3D printing technology to develop an ankle brace using metamaterial structures. It also showcases the design, manufacturing processes and testing of 3D printed customised ankle brace prototype designs that incorporated metamaterial structures. Initial tests showed that as designed, the prototype braces maintained the full range of motion for plantar flexion angles. Results also showed that the prototypes required one of the lowest moments during functional range of motion while achieving almost twice to thrice the moment required beyond the functional range of motion.