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Volleyball is a high-intensity sport characterized by repetitive jumping, sudden directional changes, and overhead movements, all of which significantly increase the risk of injuries, particularly to the shoulders, knees, and ankles. Despite the frequency of injuries caused by actions like blocking and spiking, there has been limited research focused on the specific biomechanical risk factors unique to volleyball. This study aimed to investigate the lower limb biomechanics during block jumps in both the dominant and non-dominant directions, under both anticipated and unanticipated conditions, in fifteen elite male volleyball players. Kinematic and kinetic data from the ankle, knee, and hip joints were recorded. Our results revealed statistically significant differences between the dominant and non-dominant directions at the ankle, knee, and hip joints. The non-dominant direction exhibited a greater ankle dorsiflexion angle and velocity, as well as higher knee flexion angle, velocity, moment, power, and abduction moment, along with increased hip flexion angle and power. Additionally, unanticipated movements led to increases in vertical ground reaction force (vGRF), hip extension moment, and flexion power, while ankle dorsiflexion plantarflexion velocity and knee flexion power decreased. It appears that movements in the dominant direction were stiffer and less cushioned, potentially increasing the risk of injury. While the non-dominant direction provided better shock absorption, it also elevated the knee valgus moment, which could increase the load on the knee. Furthermore, in unanticipated situations, athletes with short reaction times, unable to quickly adjust their automated movement patterns, faced a higher risk of limb overuse, thereby increasing the likelihood of injury. In practice, coaches should consider differences in limb coordination and movement direction, incorporating unilateral preventive exercises to reduce the risk of injury. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of whole-body cryotherapy (WBC) on acute recovery after a single high-intensity training day. Twelve elite professional male rowers from the national aquatic training base. They were randomly divided into a WBC group (n = 6) and a control group (CON group, n = 6). They performed a high-intensity training program, with a single session immediately followed by WBC (-110°C, 3 min) or recovered naturally for 3 min (CON group). Rowing performance, skin temperature, heart rate, blood pressure, and blood lactate concentrations were recorded before training, immediately, 5 min, and 15 min after the intervention. Blood samples were collected early in the morning of the day of intervention and that of the following day. The results indicated that 1) the blood lactate concentrations after WBC were significantly lower than pre-training ( p < 0.05); 2) the maximum power significantly decreased immediately after WBC compared to pre-training ( p < 0.05); 3) a significant main effect of time was observed for average speed, which significantly decreased after WBC ( p < 0.05); 4) a significant main effect of time for blood parameters was observed. Specifically, hematocrit, cortisol, and hemoglobin were significantly lower after WBC than pre-intervention, whereas testosterone/cortisol was significantly higher than pre-intervention ( p < 0.05). The results of this study showed that a single session of WBC had a positive effect on accelerating the elimination of blood lactate after HIT, but did not significantly change rowing performance and physiological parameters. A single session of WBC was not an effective strategy for elite rowers for acute recovery after HIT., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Huang, Dan, Wang, Ren, Liu and Li.)

Multi-core few-mode fiber based on space division multiplexing technology is widely regarded as the primary solution to the optical communication capacity issue. However, the quality of the communication signal of the multi-core few-mode fiber depends on the degree of energy coupling between the cores. Thus, we propose a heterogeneous sixteen-core four-mode fiber that achieves low inter-core crosstalk, which first employs a combination of concave and convex double-type refractive index profiles. The advantage of this double-type refractive index profile is that the fiber can more conveniently regulate the phase differences of the same modes in adjacent cores. At the wavelength of 1550 nm and the optimal fiber parameters, all cores of the proposed fiber support four LP modes, and the inter-core crosstalk of all LP modes is less than -72 dB/km. This research demonstrates the efficacy of the proposed fiber in enhancing signal quality and presents innovative ideas and solutions for the future design of various low crosstalk multi-core few-mode fiber.