Limited range of motion at the ankle joint is one of the main causes of genu recurvatum. The purpose of this study was to clarify the kinematic and electromyographic changes induced by limited ankle joint motion during gait.

Eleven healthy subjects (21.5 ± 0.8 years old) participated in this study. An ankle-foot orthosis was used to limit the ankle dorsiflexion (DF) motion from 0 to 20 degree. The gait analysis was performed at 2, 3, 4, and 5 km/h on a treadmill. The joint angles and electromyographic signals on the right side of the lower limb were measured during gait. In addition, the degree of heel elevation during the stance phase, which is a kinematic change caused by limited DF motion, was measured.

The knee angle extended significantly as DF motion was limited, whereas it flexed significantly as gait speed increased during loading response and single-limb stance phase. Rectus femoris and vastus medialis muscle activities increased significantly with increased gait speed during the same phases. Heel elevation significantly increased with limited ankle motion and increased gait speed during the stance phase.

These results suggest that genu recurvatum is influenced by gait speed. With changes in knee angle, quadriceps muscles become more activated to support the weight in the flexed knee position.

Disuse-induced capillary regression in skeletal muscle is related to overexpression of oxidative stress and/or disorder of endocapillary cell following generation of oxidative stress. We hypothesized that astaxanthin, as an antioxidant supplement, is able to attenuate oxidative stress induced by disuse, and the attenuation consequently lead to inhibit capillary regression in atrophied skeletal muscle. The purpose of the present study was to identify antioxidant effect of astaxanthin, and then to investigate preventive effects of astaxanthin on capillary regression of soleus muscle during hindlimb unloading. Twenty-four male Wistar rats were used in the present study. Rats were divided into control, control plus astaxanthin treatment, hindlimb unloaded, or hindlimb unloaded plus astaxanthin treatment group for seven days. Hindlimb unloading without astaxanthin resulted in a loss of muscle weight and a decrease of the number of capillaries. Additionally, hindlimb unloading without astaxanthin caused an overexpression of superoxide dismutase (SOD-1), and a decreased expression level of vascular endothelial growth factor (VEGF), whereas hindlimb unloading with astaxanthin maintained the expressions of SOD-1 and VEGF at the control level, prevented disuse-induced capillary regression. These results suggest that astaxanthin is effective to attenuate oxidative stress and capillary regression in disuse muscle atrophy.

The purpose of this study was to clarify the effect of the mental practice on a completely inexperienced performance that improved after short-term practice. In this study, 22 healthy subjects were randomly assigned to 2 groups: the mental practice group and the control group. The mental practice group performed mental practice during detraining, and the control group performed normal daily activities. The new movement task was“tsuki” of kendo. The distance between the center of the target and the hit point of the shinai was measured before (pre-stage) and after (post-stage) detraining for 2 weeks. The absolute error value was calculated using the distance measured at the 1st set and the 5th set of each stage (pre1, pre2, post1, and post2). Relative changes to the results in the pre1 were calculated using each parameter measured in the pre2, post1, and post2.

The results obtained in this study, showed that relative differences in the absolute error value did not significantly change between each stage in the mental practice group. However, in the control group, relative difference increased to a greater extent in post－1 than in pre2, and relative difference decreased more significantly in post2 than in pre2.

These results suggested that the effect of short-term practice was maintained by mental practice during detraining, even if the mentally practiced movement was new for the subjects.