Background: Medial tibial stress syndrome (MTSS) is one of the most common causes of exercise‐related leg pain in runners. Because stopping training due to pain from MTSS could decrease the athlete's competitiveness, it is necessary to construct MTSS prevention and treatment programs. However, the effect of running, which is believed to cause MTSS, on shear elastic modulus of the posterior lower leg is unclear. Therefore, the purpose of this study was to investigate the effect of 30 min of running on shear elastic modulus of the posterior lower leg in healthy subjects.Methods: Twenty healthy males volunteered to participate in this study (age, 20.9 ± 0.6 y; height, 169.6 ± 4.5 cm; weight, 62.6 ± 5.2 kg). The shear elastic modulus of the posterior lower leg was measured using ultrasonic shear wave elastography before and immediately after a 30‐min running task.Results: Shear elastic moduli of the flexor digitorum longus and tibialis posterior were significantly increased after 30 min running task. However, there were no significant changes in shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, peroneus longus and peroneus brevis.Conclusion: The results suggested that the increases in shear elastic moduli of flexor digitorum longus and tibialis posterior after running could be a risk factor for running‐related MTSS development.

Background: Chronic ankle instability (CAI) may result from repeated, frequent ankle sprains during sports activities. Manual examination for CAI is conducted; however, quantitative methods for the evaluation of CAI have not been established, and the reproducibility of the amount of stress is low. This cross‐sectional study aimed to use a stress device and ultrasound for the quantitative evaluation of the change in the length of the anterior talofibular ligament (ATFL) during simulated anterior drawer and ankle inversion stress tests.Methods: Questionnaires were provided to 160 healthy college students (86 men, 74 women; 320 ankles). We extracted two groups from them: control subjects without a history of ankle injury (n = 64 ankles) and subjects with CAI (n = 54 ankles). We calculated the change in the length of the ATFL with anterior drawer and inversion stress tests at ankle joint plantar flexions of 0°, 20°, and 45° using ultrasound images.Results: The anterior length change rates were significantly higher in the CAI group than in the control group at ankle joint plantar flexions of 20° and 45° in men (P < 0.05). The inversion length change rates were significantly higher in the CAI group at ankle joint plantar flexion of 20° in men (P < 0.05). No significant between‐group difference in the anterior and inversion length change rates was observed in women.Conclusions: Stress ultrasound revealed greater length changes in the ATFL in the CAI group than in the control group. The stress test may be useful at ankle joint plantar flexion of 20° for men.

In this study, the inferior fascicle of the anterior inferior tibiofibular ligament (AITFL) was classified to provide basic information to help elucidate the mechanism of ankle joint anterolateral impingement, and the morphological features of each type were compared for the purpose of clarification. This investigation examined 100 feet from 52 cadavers. The AITFL was classified into four types according to the presence or absence of the inferior fascicle and the positional relationship between the AITFL and the inferior fascicle of the AITFL. The morphological features of the AITFL that were measured included the fibre bundle length, fibre bundle width, fibre bundle angle, and the distance between the joint levels. A distinct, independent inferior fascicle of the AITFL was identified in 15 feet (15%). There were no significant differences in the morphological features based on differences in the AITFL classification. Therefore, these findings suggest that the presence or absence of the inferior fascicle and the difference in the positional relationship between the AITFL and the inferior fascicle of the AITFL are less likely to be involved in impingement during ankle dorsiflexion.

Foot-strike patterns, including rearfoot strike (RFS), midfoot strike (MFS), and forefoot strike (FFS), are related to running injuries. Additionally, cumulative load is an important parameter when considering running injuries, but the cumulative loads of Achilles tendon force (ATF), plantar fascia force (PFF), and patellofemoral joint stress (PFJS) across all foot-strike patterns, including MFS, remain unknown. This study examined the effects of different foot-strike patterns during running, including MFS, on the peak values and cumulative load of ATF, PFF, and PFJS. Twenty healthy participants were enrolled in this study. The ATF, PFF, and PFJS during barefoot running with RFS, MFS, and FFS at 10 km/h were analyzed using a three-dimensional motion capture system and force plates. Their peak values and impulse per mile (an indicator of cumulative load) were calculated. These variables were statistically compared across foot strike patterns. The significance level was adjusted using the Bonferroni method for post-hoc tests (α = 0.016). Additionally, Cohen's d was used to calculate the effect size. The peak values and cumulative loads of the ATF and PFF were highest in FFS, followed by MFS and RFS. Conversely, the peak values and cumulative loads of the PFJS were higher in RFS and MFS than in FFS. Additionally, the effect size of impulse per mile was larger than that for peak values. The load is applied to different regions depending on the foot-strike pattern. ATF and PFF showed intermediate values at midfoot strike, MFS is suggesting that it may reduce the risk of developing or exacerbating Achilles tendinopathy and plantar fasciitis. Moreover, cumulative load may be a more meaningful parameter than peak values for estimating load during actual running.

Center of pressure (COP) tracking during posture transition is an ideal scale for determining the recurrence of an ankle injury, thereby preventing chronic ankle instability (CAI). However, the same is difficult to determine because the reduced ability of certain patients (who experienced sprain) to control posture at the ankle joint is masked by the chain of hip and ankle joint motion. Thus, we observed the effects of knee joint immobilization/non-immobilization on postural control strategies during the posture transition task and attempted to evaluate the detailed pathophysiology of CAI. Ten athletes with unilateral CAI were selected. To examine differences in COP trajectories in the CAI side and non-CAI legs, patients stood on both legs for 10 s and one leg for 20 s with/without knee braces. COP acceleration during the transition was significantly higher in the CAI group with a knee brace. The COP transition from the double- to single-leg stance phase was significantly longer in the CAI foot. In the CAI group, the fixation of the knee joint increased COP acceleration during postural deviation. This suggests that there is likely an ankle joint dysfunction in the CAI group that is masked by the hip strategy.