Purpose: Given the high incidence of patellofemoral pain syndrome (PFPS) in runners, this study aimed to investigate the immediate effect of shoes with different minimalist indices (MI) on the mechanical loads of the patellofemoral joint. Methods: Fifteen healthy male rearfoot strike runners were recruited to complete overground running trials at 3.33 m/s (±5%) in two running shoe conditions (MI = 26% versus MI = 86%). The amount of ten Vicon infrared cameras (100 Hz) and two Kistler force plates (1000 Hz) were used to collect kinematic and ground reaction force (GRF) data simultaneously. Quadriceps strength, patellofemoral contact force, patellofemoral contact area, and patellofemoral contact stress were calculated. Results: No significant differences were observed in the impact force and the second peak of the vertical GRF between the two shoe conditions. Compared to wearing low-MI shoes, wearing high-MI shoes showed that the maximum flexion angle of the knee, the contact area of patellofemoral joint and the peak knee extension moment reduced significantly (p < 0.01), and the peak patellofemoral contact force and stress decreased significantly (p < 0.05). Conclusion: These findings suggest that wearing high-MI shoes significantly decreases the patellofemoral contact force and patellofemoral joint stress by reducing the moment of knee extension, thus effectively reducing the load of the patellofemoral joint during the stance phase of running and potentially lowering the risk of PFPS.

Objectives: To explore the effects of wearing compression garments on joint mechanics, soft tissue vibration and muscle activities during drop jumps. Methods: Twelve healthy male athletes were recruited to execute drop jumps from heights of 30, 45 and 60 cm whilst wearing compression shorts (CS) and control shorts (CON). Sagittal plane kinematics, ground reaction forces, accelerations of the quadriceps femoris (QF), hamstrings (HM) and shoe heel-cup, and electromyography images of the rectus femoris (RF) and biceps femoris (BF) were collected. Results: Compared with wearing CON, wearing CS significantly reduced the QF peak acceleration at 45 and 60 cm and the HM peak acceleration at 30 cm. Wearing CS significantly increased the damping coefficient for QF and HM at 60 cm compared with wearing CON. Moreover, the peak transmissibility when wearing CS was significantly lower than that when wearing CON for all soft tissue compartments and heights, except for QF at 30 cm. Wearing CS reduced the RF activity during the pre-, post-, and eccentric activations for all heights and concentric activations at 45 cm; it also reduced the BF activity during post- and eccentric activations at 30 and 60 cm, respectively. The hip and knee joint moments and power or jump height were unaffected by the garment type. Conclusion: Applying external compression can reduce soft tissue vibrations without compromising neuromuscular performance during strenuous physical activities that involve exposure to impact-induced vibrations.

Purpose: Although the Achilles tendon (AT) is the largest and strongest tendon, it remains one of the most vulnerable tendons among elite and recreational runners. The present study aims to explore the effects of 12-week gait retraining (GR) on the plantar flexion torque of the ankle and the morphological and mechanical properties of the AT. Methods: Thirty-four healthy male recreational runners (habitual rearfoot strikers) who never tried to run in minimal shoes were recruited, and the intervention was completed (20 in the GR group vs. 14 in the control (CON) group). The participants in the GR group were asked to run in minimal shoes (INOV-8 BARE-XF 210) provided by the investigators with forefoot strike patterns during the progressive 12-week GR. Meanwhile, the participants in the CON group were instructed to run in their own running shoes, which they were familiar with, with original foot strike patterns and intensities. The morphological properties of the AT, namely, length and cross-sectional area (CSA), were obtained by using an ultrasound device. A dynamometer was utilized simultaneously to measure and calculate the plantar flexion torque of the ankle, the rate of torque development, the peak force of the AT, and the stress and strain of the AT. Results: After 12-week GR, the following results were obtained: (1) A significant time effect in the peak ankle plantarflexion torque was observed (p = 0.005), showing a 27.5% increase in the GR group; (2) A significant group effect in the CSA was observed (p = 0.027), specifically, the increase in CSA was significantly larger in the GR group than the CON group; (3) A significant time effect in the peak AT force was observed (p = 0.005), showing a 27.5% increase in the GR group. Conclusion: The effect of 12 weeks of GR is an increase in AT CSA, plantar flexor muscle strength of the ankle, and peak AT force during a maximal voluntary isometric contraction test. These changes in AT morphology and function could be positive for tendon health and could prevent future AT injury.

Purpose: This study aimed to explore the relationship between foot loading and comfort perception in two basketball shoes during basketball-specific maneuvers. Methods: Twelve male collegiate basketball players were required to complete three basketball maneuvers (i.e., side-step cutting, 90° L-direction running, and lay-up jumping) in two basketball shoe conditions (shoe L and shoe N, with different midsole cushioning types). Two Kistler force plates and a Medilogic insole plantar pressure system were used to collect kinetic data (i.e., impact force, peak loading rate, and plantar pressure variables). Perception scales were used to evaluate comfort perception. Results: No significant difference was observed between the two shoes during maneuvers in terms of ground reaction force. However, the plantar pressure of shoe L in the midfoot and lateral foot regions was significantly greater than that of shoe N during side-step cutting and lay-up jumping. Shoe N was significantly superior to shoe L, especially in dynamic scale in terms of the perception of comfort. The plantar pressure and perception characteristics in the two shoes were significantly different but inconsistent with each other. Conclusion: The biomechanical characteristics of the shoes themselves and the perception evaluation of the athletes should be considered in comprehensive shoe-cushioning design and evaluation.

This study aims to investigate the effects of wearing high-top and low-top basketball shoes on the ankle joint kinematics, kinetics and performance in the sagittal plane during weight-bearing dorsiflexion (WB-DF) movement and lay-up jump. Twelve subjects performed WB-DF movement and lay-up jumps (LU) in two shoe conditions. Wearing HS can significantly reduce ankle joint excursion in WB-DF. No significant differences were found in jumping height and kinematics between the two shoes. In LU, peak plantarflexion torque and power were significantly lower in HS. The high-top shoes adopted in this study did not restrict the ankle dorsiflexion performance during actual jumping. But it is suggested that the greater power in LS during LU may have a greater potential in the actual game with different conditions, such as the distance of the shot and opposition. Thus, high shoe collar height would be applied to practical with the caution of affecting the partial kinetic characteristics of the ankle joint in the sagittal plane.