Chen Yang

Footwork plays a crucial role in the stroke performance of athletes, yet its underlying foot support patterns remain underexplored. This study aimed to compare the biomechanical differences in lower limb joints between alternating foot support pattern (ASP) and full-foot support pattern (FSP) in table tennis footwork. Twelve national level I male table tennis athletes participated in a within-subject design, performing both foot support patterns. Compared with ASP, FSP showed significantly lower peak hip power generation (10.38 ± 1.42 W/kg), lower ankle power generation and absorption, with reduced ankle rates of change. In addition, the relative contribution of ankle power generation (1.25 ± 1.60%) decreased, leading to a higher combined contribution of the hip (93.62 ± 3.76%) and ankle (4.96 ± 4.46%) joints. The peak time of ankle power absorption was significantly delayed. By contrast, the relative contributions of hip and knee power generation were higher in FSP than in ASP. Overall, hip joint function serves as the primary source of positive work in both ASP and FSP. FSP reduced ankle joint contribution, with the hip and knee joints compensating for this limitation during the stroke. Athletes should actively adjust their movements according to the characteristics of the foot support pattern.

This study aims to develop a computational model to assess the cumulative probability of meniscal failure in the knee joint during running. The knee joint forces of twelve male participants were measured while running at speeds of 9 km/h, 12 km/h, and 15 km/h. These forces were used as boundary conditions in a finite element model. The proportion of high-stress elements in the meniscus during the support phase was calculated, and a Weibull distribution-based failure model was used to compute the cumulative injury probabilities of the meniscus over 360 days at the three running speeds. Running speed had a significant main effect on this ratio(p = 0.041, F = 3.393, ηp2 = 0.117), the ratio during the stance phase at 15 km/h was greater than at 9 km/h(p = 0.036, F = 5.402, Cohen’s d = 1.248), but this difference was not statistically significant when compared to 12 km/h(p = 0.513, F = 1.068, Cohen’s d = 0.224); similarly, there was no significant difference between 9 km/h and 12 km/h(p = 0.139, F = 1.335, Cohen’s d = 0.921). Faster running speeds result in higher knee joint reaction forces, however, the probability of meniscal failure is lower. The risk of meniscal failure is more strongly associated with the frequency of stress applications than with the magnitude of the stress itself. Slower running speeds require more gait cycles to complete the same running distance, thereby prolonging loading duration and increasing the number of stress applications.

Purpose: This study investigated the effect of anteromedial (AM) and central anterior cruciate ligament (ACL) reconstructions on the patellofemoral joint (PFJ) contact mechanics during walking and running.Methods: Six knee models were established under a musculoskeletal multibody dynamic framework. The ACL attachment points and muscle volume of the quadriceps femoris and hamstrings were modified to simulate ACL reconstructions and post-operative muscle atrophy. Walking and running simulations were performed to quantify ACL graft force and PFJ contact force. A single stance phase of the motion cycle was divided into eleven time points (periods 0.0-1.0). The computational results were statistically tested at each time point.Results: The results showed that central ACL reconstruction reduced graft force at contralateral toe-off and toe-off phases under walking conditions and the entire cycle under running conditions, with maximal reductions were 10.96 ± 7.42 % and 29.00 ± 10.41 %, respectively. Compared to AM reconstruction, central reconstruction increased the mean PFJ contact force by up to 2.12 ± 1.17 % of body weight during periods 0.4-0.9 of the walking cycle and exhibited a complex pattern during the running cycle.Conclusions: Central ACL reconstruction provided a significantly higher PFJ load compared with AM reconstruction during walking after surgery. No consistent conclusions were reached between the two surgical protocols on PFJ contact force during running. These findings provide clinicians with a better understanding of the PFJ mechanics after ACL reconstruction.

This study aimed to investigate the impact of different foot support patterns on knee joint loading in elite table tennis athletes. Eighteen right-handed with shake-hand grip, national I level table tennis athletes were included. Their average age was 20.33 ± 1.53 years, with a height of 1.73 ± 0.08 meters, weight of 66.75 ± 9.35 kilograms, and 11.67 ± 1.81 years of training experience. The athletes performed forehand loop strokes using different support patterns: alternating support pattern (ASP) and full-foot support pattern (FSP). Kinematic and kinetic data were collected using 8 infrared cameras and 3 force plates. Compared to the ASP, the FSP significantly reduced heel-to-forefoot rotation angle (−30.67%), knee compressive force (−9.14%), knee extension moments (−13.94%), hip (−5.6%) and thorax (−3.8%) Z-axis angular speed, but increased free moment by 19.92%. The moment graph also revealed the FSP had a higher knee internal rotation moment (0%∼69%) and external rotation moment (70%∼100%), as well as a higher hip external rotation moment (6%∼64%). The FSP decreased athletic performance and increased knee joint load during the forehand loop. It is recommended that athletes avoid using the FSP during training or competition.

Baseball hitting involves multiple biomechanical variables, and understanding their impact on bat energy is crucial for improving performance. However, no studies have explored how biomechanical features affect hitting performance from the perspective of bat energy. This study aimed to systematically investigate the influence of lower limb biomechanical variables on bat energy using factor analysis and stepwise regression methods. Sixteen right-handed baseball players participated in the study. Bilateral lower limb kinematic and kinetic features were calculated and exported using a motion capture system and force platform. Six key factors (F1–F6) were extracted from the 28 biomechanical features. Factors F1 and F5 are correlated with the rotation of the trailing and leading limbs, respectively; F2 correlates with energy production of the leading limb; F3 correlates with linear momentum production; F4 correlates with body posture control; and F6 correlates with body linear movement in the anterior direction. To enhance bat energy, hitters should step towards the incoming ball more rapidly to increase ground reaction force on the leading limb. They should also maximize extension and external rotation of both the leading and trailing limbs, stabilize the trailing limb during body rotation, and ensure proper weight distribution between the leading and trailing limbs.

The effectiveness of plyometric training in adolescent basketball players has not been fully elaborated, especially its effect on enhancing change of direction abilities. Thirty male adolescent basketball players were divided into plyometric and resistance training groups for an 8-week training period. The improvement in change of direction abilities before and after the training was assessed using the Lane Agility Drill test. Motion capture system, force platforms, and electromyography were utilized to investigate the characteristics of lower limb kinematic and kinetic features before and after training. At post-test, the Lane Agility Drill finish time for the plyometric group was significantly less than that of the resistance training group ( P < 0.05, Cohen's d = 0.551), and the post-test Lane Agility Drill finish time for the plyometric group was significantly less than their pre-test time ( P < 0.05, Cohen's d = 0.746). At post-test, the plyometric training group showed greater increases in peak impulse ( P < 0.05, Cohen's d = 0.464), peak power ( P < 0.05, Cohen's d = 0.684) compared to resistance training group. The study's conclusion indicates that compared to resistance training, plyometric training more significantly enhances athletes’ change of direction abilities. This improvement is attributed to the superior transfer of strength and explosive power gains acquired during training. Additionally, plyometric training optimizes energy utilization and production during jumping and running.