Ankle Muscle Activations during Different Foot-Strike Patterns in Running.

This study analysed the landing performance and muscle activity of athletes in forefoot strike (FFS) and rearfoot strike (RFS) patterns. Ten male college participants were asked to perform two foot strikes patterns, each at a running speed of 6 km/h. Three inertial sensors and five EMG sensors as well as one 24 G accelerometer were synchronised to acquire joint kinematics parameters as well as muscle activation, respectively. In both the FFS and RFS patterns, according to the intraclass correlation coefficient, excellent reliability was found for landing performance and muscle activation. Paired t tests indicated significantly higher ankle plantar flexion in the FFS pattern. Moreover, biceps femoris (BF) and gastrocnemius medialis (GM) activation increased in the pre-stance phase of the FFS compared with that of RFS. The FFS pattern had significantly decreased tibialis anterior (TA) muscle activity compared with the RFS pattern during the pre-stance phase. The results demonstrated that the ankle strategy focused on controlling the foot strike pattern. The influence of the FFS pattern on muscle activity likely indicates that an athlete can increase both BF and GM muscles activity. Altered landing strategy in cases of FFS pattern may contribute both to the running efficiency and muscle activation of the lower extremity. Therefore, neuromuscular training and education are required to enable activation in dynamic running tasks.

The Effect of Divided Attention with Bounce Drop Jump on Dynamic Postural Stability.

This study determined the effect of divided attention on controlling postural stability during a drop vertical jump task. In total, 30 participants were tested for drop vertical jumps from a 30-cm high platform and landing on a single leg with or without divided attention tasks. Three-dimensional marker trajectories and ground reaction forces were collected simultaneously. Vertical ground reaction force, loading rate, and dynamic postural stability index were analyzed with or without divided attention tasks. The paired sample t test indicated a significantly low knee flexion angle, high vertical ground reaction force, and increased loading rate in the divided attention task. Moreover, participants showed an increased vertical stability index and dynamic postural stability index in the divided attention task than in the nondivided attention task. Thus, results demonstrated that the divided attention task could affect posture control, leading to poor dynamic posture stability and possibly increasing lower extremity injury risk. The influence of the divided attention task on movement quality likely indicates that an athlete can no longer focus his attention on the bounce drop jump maneuver. Therefore, the bounce drop jump combined with dynamic postural stability index could be used in posture stability screening.

Are Landing Biomechanics Altered in Elite Athletes with Chronic Ankle Instability.

This study analyzed landing strategies used by athletes with chronic ankle instability (CAI) and copers compared to uninjured controls. Thirty participants were asked to perform a single-leg forward jump followed by a single-leg landing. Compared to uninjured controls, those with CAI athletes had significantly greater hip flexion and ankle eversion angles at initial landing, suggesting preference for using hip movements and extra ankle eversion angles to avoid ankle inversion when landing. CAI athletes were also found to have significantly decreased peroneus longus activation and higher ankle inversion velocity were both found during descending phase. And these were potential contributors to cause ankle inversion injury as there were likely many others. Based on these findings, CAI athletes may need to utilize more multi-joint or multi-muscle strategies during landing to maintain stability and prevent re-injury.

Analysing lower limb motion and muscle activation in athletes with ankle instability during dual-task drop-jump.

This study investigates the impact of chronic ankle instability (CAI) on athletes' lower extremity mechanics during bounce drop-jump landings with divided attention. Thirty Division I physical education voluntarily participated in the study. They performed two sets of bounce drop jumps: one set with a divided attention task and the other without. The obtained data were analysed using a paired t-test to compare the outcomes between the divided attention (DA) and non-divided attention (NDA) tasks. Athletes with CAI, during the DA task, displayed higher vertical landing forces, increased ankle inversion velocity, and greater range of motion of the ankle, knee, and hip in the frontal and transverse planes. They also exhibited insufficient neuromuscular preparation of the rectus femoris muscle. Notably, distinct kinematic alterations were observed in the ankle, knee, and hip joints regarding frontal and transverse lower-extremity kinematics. The findings suggest that athletes with CAI experience decreased activation of the rectus femoris muscle, which may impact their dynamic postural stability from pre-landing to ascending phases. Furthermore, the results indicate that individuals with CAI closely replicate the injury mechanisms encountered during a drop-jump landing task with divided attention. These insights offer valuable information about the real-time challenges faced by athletes with CAI.

Effects of Jump-Rope-Specific Footwear Selection on Lower Extremity Biomechanics.

Footwear is among the most important equipment in sports to decrease injuries and enhance performance during exercise. In this study, we investigated differences in lower extremity plantar pressure and muscle activations during jump rope activities. Ten participants performed jump rope under two landing conditions with different footwear. A force platform (AMTI, 1000 Hz), a Novel Pedar-X system (Nove, 100 Hz), and a wireless electromyography (EMG) system (Noraxon, 1500 Hz) were used to measure biomechanical parameters during the jump rope exercise. Vertical ground reaction forces (vGRF), plantar pressure, and lower extremity muscle activations were analyzed. One-leg landing resulted in a significantly greater vGRF and shorter fly time than two-leg landing (p < 0.05). A significantly higher peak pressure and lesser toe (LT) area pressure was shown with the jumping shoe (all p < 0.05), but lower plantar pressure resulted in the middle foot area (p < 0.05). The EMG results of tibialis anterior (TA) were significantly greater with one-leg landing (all p < 0.05) during the pre- and background activity (BGA) phases. The results suggest that plantar pressure distribution should be considered when deciding on footwear during jump rope exercises, but care should be taken with regards to recovery after repeated collisions and fatigue. The jumping shoe provides benefits in terms of decreased plantar pressure sustained during jump rope exercises.

Influence of Landing in Neuromuscular Control and Ground Reaction Force with Ankle Instability: A Narrative Review.

Ankle sprains are generally the most common injuries that are frequently experienced by competitive athletes. Ankle sprains, which are the main cause of ankle instability, can impair long-term sports performance and cause chronic ankle instability (CAI). Thus, a comprehensive understanding of the key factors involved in repeated ankle strains is necessary. During jumping and landing, adaptation to the landing force and control of neuromuscular activation is crucial in maintaining ankle stability. Ankle mobility provides a buffer during landing, and peroneus longus activation inhibits ankle inversion; together, they can effectively minimize the risk of ankle inversion injuries. Accordingly, this study recommends that ankle mobility should be enhanced through active and passive stretching and muscle recruitment training of the peroneus longus muscles for landing strategies should be performed to improve proprioception, which would in turn prevent ankle sprain and injury to neighboring joints.

Effects of Shoe Midsole Hardness on Lower Extremity Biomechanics during Jump Rope in Healthy Males.

This study investigated differences in lower extremity muscle activations and vertical stiffness during a 2.2 Hz jump rope exercise with different midsole hardnesses (45, 50, 55, and 60 Shores C). Twelve healthy male participants wore customized shoes with different hardness midsoles and performed jump rope exercises in a random order. A nine-camera motion analysis system (150 Hz), a force platform (1500 Hz), and a wireless electromyography (EMG) system (Noraxon, 1500 Hz) were used to measure the biomechanical parameters during the jump rope exercise. The biceps femoris %MVC of barefoot participants was significantly greater than that of those wearing the 45 Shores C (p = 0.048) and 55 Shores C (p = 0.009) midsole 100 ms before landing. The vastus medialis %MVC of barefoot participants was significantly greater than that of those wearing the 55 C midsole (p = 0.005). Nonsignificant differences in vertical stiffness were found between midsole hardnesses and barefoot. Lower extremity muscle activation differed between conditions. The results of this study indicate that for repetitive activities that entail multiple impacts, sports shoes with a low midsole hardness (e.g., 50 Shores C or 45 Shores C) may be appropriate. It is important to provide customers with information regarding midsole hardness in shoe product labeling so that they properly consider the function of the shoes.

Potential of a simple solid-phase extraction method coupled to analytical and bioanalytical methods for an improved determination of microcystins in algal samples.

Artemia assays and protein phosphatase assays are commonly used for the screening of microcystins (MCs) in algal samples instead of the standard mouse toxicity assay. However, it has been shown that their results are often biased because of the matrix effects. To eliminate the possible interferences in the algal matrices, a new solid-phase extraction (SPE) method using silica gel as a sorbent was developed and evaluated. Results show that this SPE method could not only reduce the toxicity of the Microcystis samples towards brine shrimp by 50-80% but also eliminate 90-100% of the endogenous phosphatase activity from Spirulina and Chlorella samples, thus improving the determination of microcystins in algal samples using either of the two bioanalytical methods. The application of this SPE method as an off-line cleanup for high-performance liquid chromatography (HPLC) with UV detection is also described in this study. After SPE, the HPLC chromatograms of Microcystis samples have clear baselines that have no interferences with the analyte peaks.