Sports Biomechanics最新文献

Whole-body Angular momentum (AM) is a key factor for jump execution and landing stability in figure skating. However, its generation mechanism in the triple loop (T-LP) remain underexplored. The aim of this study was to address this gap by analysing the segmental contributions to angular momentum generation. Ten female skaters performed the T-LP while undergoing three-dimensional motion analysis. Although the AM increased first due to the contribution of the upper limbs during the glide phase, the AM of the lower limbs increased more significantly during the transition phase, with a particularly notable contribution from the non-supporting leg. A slight reduction in AM was observed during the Pivot phase just before take-off. These findings suggest that, unlike off-ice jumps where AM is typically generated by the arms and trunk, T-LP on ice involves a different strategy. Furthermore, no significant correlation was found between AM at take-off and key jump performance parameter such as jump height, rotational velocity, or flight time. This suggests that optimal jump execution requires coordinated integration of other biomechanical factors, including take-off mechanics and aerial posture control. These insights may aid in refining training strategies and optimising jump mechanics in figure skating.

Despite advances in footwear industry, running related injuries (RRI) rate is high in female runners. Selection of proper shoe is a big challenge for runners. We aimed to compare the effects of running-induced fatigue on ground reaction forces and free moments while using neutral (N-Shoes), motion control (MC-Shoes), and minimalist shoes (M-Shoes) in forefoot runner females. Twenty recreational female forefoot runners completed fatiguing treadmill running protocol using M-Shoes, MC-Shoes and N-Shoes in three separated sessions. Participants ran on a runway at 3.3 m/s before and after fatiguing protocol in each session. Using N-shoes increased peak lateral force, peak braking force, peak propulsive force, peak vertical force, peak positive free moment, peak negative free moment, load rate, medio-lateral impulse, antero-posterior impulse and vertical impulse. Using MC-shoes, increased peak vertical and peak braking forces and vertical impulse, and decreased peak lateral force and peak negative and positive free moments. While, using M-shoes increased peak braking forces. Minimalist shoes maintain pre-fatigue ground reaction forces and free moments during fatigued running compared to neutral and motion control shoes in female forefoot runners. Using minimalist shoes is recommended to decrease exacerbated running-induced fatigue effects in forefoot runner females.

Although trampolinists rely heavily on visual cues, visual criteria have not been introduced into predictive simulations yet. We aimed to introduce visual criteria into predictive simulations of the backward somersault with a twist and the double backward somersault in pike position including 1½ twists in the first somersault and ½ twist in the second somersault to generate innovative and safe optimal acrobatic techniques. A gradient of different weightings, ranging from none to large visual weights, was tested to find a good compromise between visual vs kinematics objectives. Four international coaches and two international judges assessed animations of the optimal techniques and of an elite athlete's technique, providing insights into the acceptability of the optimal techniques. For the most complex acrobatics, coaches found all optimal techniques more efficient for aerial twist creation. However, they perceived them as less safe, less realistic, similarly aesthetic, and similarly appropriate for visual information intake compared with the athlete's technique. Judges assigned fewer deductions to the simulated techniques than to the athlete's performance. The optimal techniques with visual criteria were more similar to the athlete's technique, highlighting the importance of including visual criteria into the optimisation of acrobatics to create innovative techniques that athletes will be able to use.

In breaststroke, leg kick propulsion plays a major role in swimming velocity; however, the relationship between propulsive force and its kinematics remains underexplored. This study aimed to identify leg movements that enhance foot propulsive force. Fourteen male swimmers performed 10 seconds of maximal-effort breaststroke kicks while holding a board with their upper limbs in a swimming flume. Leg kinematics and foot propulsive force were measured using a motion-capture system and eight pressure sensors on the left foot. During the knee extension phase, foot propulsive force correlated significantly with hip adduction/abduction range of motion (ROM) (r = -0.57), ankle plantar/dorsiflexion ROM (r = 0.59), mean plantar/dorsiflexion angular velocity (r = 0.56), peak knee extension angular velocity (r = -0.54), and peak ankle plantar flexion angular velocity (r = 0.59). In the insweep phase, foot propulsive force correlated significantly with foot resultant speed (r = 0.89), foot forward-backward velocity (r = 0.79), and foot vertical velocity (r = 0.71). This study suggests that during the knee extension phase, adjustments in ROM and increases in angular velocity of lower limb joints are associated with greater foot propulsive force, while higher foot velocity is associated with increased propulsive force during the insweep phase.

The Russian bar is an acrobatic circus discipline characterised by dynamic loading on a single shoulder, posing a risk for back injuries. The aim of this case study was to quantify and compare lumbar spine loads in porters using a novel symmetrical design and the traditional asymmetrical bar. Two male porters and one female flyer performed a series of candle jumps, saltos, and consecutive jumps using both bar designs. Motion capture, electromyography, and musculoskeletal modelling in OpenSim were used to quantify L4-L5 intervertebral forces and moments. Statistical comparisons were conducted using a multifactorial analysis of variance (ANOVA). The results showed that the symmetrical bar significantly reduced lumbar spine bending moments (2.1 times lower) and shear forces (2.2 times lower) compared to the traditional bar, with no significant differences in shoulder forces. Shoulder forces did not differ significantly between bar types, suggesting that the flyer's performance, particularly jump height, was not substantially affected by the change in bar design. This novel symmetric bar design may enhance the safety and carrier of Russian bar porters. Future research should investigate the long-term effects of this design and its impact on performance adaptation.

Knee osteoarthritis (OA) is a common degenerative joint condition with significant public health implications. Modifying running biomechanics is a potential strategy to reduce knee joint loading and support long-term maintenance of physical activity in individuals with knee OA. This study investigated the effects of running modifications on knee contact force (KCF) between natural running, forefoot striking (FFS), and toe-out running. Ten healthy participants performed three trials of 20-m overground running for each condition. KCF were estimated using an OpenSim-based musculoskeletal model, and differences across conditions were evaluated using a one-way repeated measures ANOVA. In early stance, toe-out running exhibited higher medial-lateral KCF compared to both natural running (p = 0.017, Cohen's d = 0.92) and FFS (p = 0.003, Cohen's d = 1.28). In late stance, both FFS (p = 0.039, Cohen's d = 0.76) and toe-out (p = 0.011, Cohen's d = 1.01) running exhibited increased medial-lateral KCF relative to natural running. Additionally, FFS generated significantly higher vertical KCF than both natural (p < 0.001, Cohen's d = 2.32) and toe-out running (p < 0.001, Cohen's d = 1.70). Running modifications involving toe-out or FFS resulted in increased KCF, particularly in the medial-lateral direction. These findings suggest such modifications may not effectively reduce joint loading and should be approached with caution in individuals with knee OA.

The iliotibial band (ITB) stabilises the hip and knee joints during running, but excessive strain can lead to iliotibial band syndrome (ITBS), a common overuse injury in runners. This study aimed to determine if running around a curve influences ITB strain using a musculoskeletal model with active and passive ITB strands. Sixteen runners completed trials running straight and around a curve, with kinematic and ground reaction force data collected. An ITB model incorporating gluteus maximus and tensor fascia latae muscles, along with a passive strand, was used. Peak strain values during the stance phase were averaged across subjects. Results indicated no significant peak strain differences in active muscle strands between conditions. However, the peak passive strand strain was significantly higher with the leg on the inside of the curve (4.69%) compared to the outside curve condition (4.49%) (p = .009, η² = 0.454), but not significantly different from the straight path condition. When running around a curve, this may put the inside leg at a higher risk of developing ITBS when compared to the outside leg. Further research is needed to explore the long-term effects of curved running on ITB strain and potential injury prevention strategies.

This study evaluated the acute fatigue-inducing effect of distance running on kinematics and kinetics during overground running. Standardised mean differences (SMD) with 95% confidence intervals (95% CI) were used to pool data across 16 studies. Effects during consistent (pre- and post-fatigue running speed within ± 5%) versus varied speed running (difference of >5% between running speeds) were analysed separately. There was strong evidence that running-induced fatigue significantly increases ground contact times at consistent running speeds (SMD 0.52 [95% CI 0.22, 0.82]) and moderate evidence that step length shortens at varied running speeds (SMD -1.27 [95% CI -1.79, -0.75]). There was strong evidence that fatigue does not change peak: hip and knee flexion angles, hip adduction angle, hip and knee internal rotation angles, hip and knee extension moments, hip and knee abduction moments, knee abduction angle, knee flexion and extension moments, knee adduction moment, rearfoot eversion angle, and plantarflexion moments, or knee flexion and plantarflexion range of motion during stance. Running-induced fatigue increases contact times and reduces step length, whereas lower-body joint angles and moments are unchanged. Minimising changes in stride parameters could provide a mechanism for reducing the effects of fatigue on running performance.

This study aims to investigate the different ground reaction force (GRF) characteristics from different stride types. This study included 30 Taiwanese elite college and professional baseball pitchers. Each pitcher was classified into one of the following stride types: tall and fall (TF), dip and drive (DD), or mixed (MX). Our findings indicated that DD pitchers pressed their bodies forward earlier than TF pitchers. In contrast, the GRF of the pivot leg of TF pitchers increased slowly in the first half of the stride phase and continued to increase even after the stride leg touched the ground. This type of continuous pressing in TF was different from that in DD and MX pitchers, which decreased rapidly into the arm-cocking & acceleration phases. We conclude that the lower extremities were used differently by TF, DD and MX pitchers. This information could serve as a training guideline for coaches and pitchers to enhance training effectiveness, while simultaneously lowering injury risks.

This study examined whether an inertial measurement unit (IMU) could measure ground reaction force (GRF) during a cricket fast bowling delivery. Eighteen male fast bowlers had IMUs attached to their upper back and bowling wrist. Each participant bowled 36 deliveries, split into three different intensity zones: low = 70% of maximum perceived bowling effort, medium = 85%, and high = 100%. A force plate was embedded into the bowling crease to measure the ground truth GRF. Three machine learning models were used to estimate GRF from the IMU data. The best results from all models showed a mean absolute percentage error of 22.1% body weights (BW) for vertical and horizontal peak force, 24.1% for vertical impulse, 32.6% and 33.6% for vertical and horizontal loading rates, respectively. The linear support vector machine model had the most consistent results. Although results were similar to other papers that have estimated GRF, the error would likely prevent its use in individual monitoring. However, due to the large differences in raw GRFs between participants, researchers may be able to help identify links among GRF, injury, and performance by categorising values into levels (i.e., low and high).