Quantitative analysis of approximate shapes in a myofiber cross-section and their relationship with myofiber cross-sectional area.

[Purpose] Although the shapes observed in myofiber cross-sections have been subjectively identified as polygonal, precise methodologies to classify such shapes have not been elucidated previously. Therefore, we aimed to determine the approximate shapes found in myofiber cross-sections, and to elucidate their relationship with the myofiber cross-sectional area. [Materials and Methods] Soleus muscles of five 11-week-old male Wistar rats were collected as specimens. The muscle specimens were rapid-frozen in isopentane-cooled in dry ice and acetone-and sliced into 10-µm slices in a cryostat and stained with hematoxylin-eosin. The NIH ImageJ software was used to analyze the number of corners that were counted according to the proposed criteria and the myofiber cross-sectional areas of 500 myofibers. [Results] In assessments of the approximate shapes of myofiber cross-sections, the proportion of pentagons was 41%, which was the highest among polygons. A weak positive correlation was noted between the corner count and myofiber cross-sectional area, which indicated that polygons with more corners were associated with a larger myofiber cross-sectional area. [Conclusion] The myofiber cross-sections of the soleus muscle were considered to frequently show an approximately pentagonal shape. Moreover, a correlation was observed between the myofiber cross-section shape and myofiber cross-sectional area, suggesting that the area was also associated with the relevant functional features.

Effects of an external foci of attention at different distances on standing long jump in non-athletes.

[Purpose] External focus (EF) instructions demonstrate a learning effect on motor performance enhancement. However, the effective EF distance during standing long jump performance of non-athletes has not been clarified. This study aimed to determine the effects of EF at different distances on jumping performance. [Participants and Methods] A total of 40 non-athlete participants were randomly divided among four groups. The no attention line group performed a standing long jump without the attention line on the floor; those in the -20-cm EF group, the ± 0-cm EF group, and +20-cm EF group performed the jump attention line with an attention line 20-cm posterior, at ± 0 cm, and 20-cm anterior as the reference jump distances, respectively. [Results] The mean rate of increase between the first to second jump distances in the +20-cm EF group was higher than that in the no attention line group. The rates at which the jumpers reached the attention line in the ± 0-cm EF group and the +20-cm EF group were lower than the rate in the -20-cm EF group. [Conclusion] Instructions are more effective when the distance to the attention line exceeds jumping performance.

Effects of antagonistic muscle contraction exercises on ankle joint range of motion.

[Purpose] Antagonistic stretching is an important therapeutic program in rehabilitation. However, if pain occurs during stretching, other methods should be considered. This study aimed to investigate whether antagonistic muscle contraction exercises alone had an effect in expanding the joint range of motion. [Participants and Methods] Participants included 50 healthy males and females (aged 21.0 ± 3.1 years) who were each randomly assigned to one of four groups that performed either active, resistance, phasic, or isometric exercises or a control group that performed no exercise. Each exercise group performed five sets of 30-second ankle dorsiflexion exercises. Active and passive ranges of motion of ankle dorsiflexion were measured using a goniometer, with the participants in the knee extension and flexion positions. [Results] Ankle joint range of motion was increased in the knee extension position in the isometric exercise group. There were no other differences observed in any of the groups. [Conclusion] Our results indicated that isometric exercises had an immediate effect on increasing ankle joint range of motion. This is presumably attributed to the effects of Golgi tendon organ inhibition (Ib inhibition) or stretch tolerance of the gastrocnemius muscle.

Gender difference in factors affecting the medial longitudinal arch height of the foot in healthy young adults.

[Purpose] Medial longitudinal arch (MLA) height is associated with various injuries and diseases and gender differences, if any. This study aimed to examine factors affecting the MLA height associated with gender differences in healthy subjects with no orthopedic disorders. [Subjects and Methods] This study included 36 healthy adults (19 males, 17 females; mean age, 21.8 ± 3.6 years; body mass index, 21.1 ± 2.0 kg/m2). Their height, body weight, foot length, muscle strength of the tibialis posterior muscle (TPM), toe-gripping strength, hallux valgus angle, inversion microdactylia angle, angle of leg-heel alignment, femoro-tibial angle, and navicular height were measured. Correlation between the ratio of arch height and other measurement parameters was examined. [Results] In females, the ratio of arch height was significantly positively correlated with muscle strength of the TPM and toe-gripping strength and negatively correlated with the hallux valgus angle and the leg-heel alignment, whereas in males, only a positive correlation between the ratio of arch height and muscle strength of the TPM was observed. [Conclusion] These results reveal that etiological mechanisms determining MLA height are different between males and females. Overall, the present results indicate that further studies identifying causes of MLA height variation must include gender-based analysis.

Alteration of cathepsin-D expression in atrophied muscles and apoptotic myofibers by hindlimb unloading in a low-temperature environment.

[Purpose] The purpose of this study was to elucidate the cathepsin-D involvement in signaling pathways for the survival and apoptosis of myofibers in rats with hindlimb-unloading in a low-temperature environment. [Subjects and Methods] Wistar rats were divided into two groups: a control group and a group that underwent hindlimb unloading in a low-temperature environment to induce muscle apoptosis. Cathepsin-D localization in the soleus and extensor digitorum longus muscles, along with the expression of cathepsin-D in apoptotic myofibers, was examined. Expression of the active and inactive forms of cathepsin-D was also analyzed. [Results] Cathepsin-D was mainly expressed in type I myofibers and was observed to have punctate patterns in the control group. In the hindlimb unloading in a low-temperature environment group, the type I myofiber composition ratio decreased, and caspase-3 activation and TUNEL-positive apoptotic myofibers were observed. In caspase-3-activated myofibers, cathepsin-D overexpression and leakage of it into the cytoplasm were observed. In the hindlimb unloading in a low-temperature environment group, the amount of inactive cathepsin-D decreased, whereas that of the active form increased. [Conclusion] Cathepsin-D was deduced to be indicative of a myofiber-type classification and a factor related to myofiber type maintenance. In addition, cathepsin-D leakage into the cytoplasm was appeared to be involved in caspase-3 activation in the hindlimb unloading in a low-temperature environment group.

The improvement effect of limited mental practice in individuals with poststroke hemiparesis: the influence of mental imagery and mental concentration.

[Purpose] This study examined whether limited mental practice improves the motor performance of poststroke individuals with hemiparesis. [Subjects] Twenty-three participants with poststroke hemiparesis (40-82 years of age) participated in this study. [Methods] The subjects were divided into four groups with respect to a dart-throwing task: the no-practice, physical practice only, mental practice only, and mental and physical practice groups. The groups were compared in terms of gains in motor performance, mental imagery vividness, and level of concentration during mental practice. [Results] No statistically significant difference was found for gains in motor performance among groups, and there was no correlation between imagery vividness and motor performance gains. However, a correlation was found between gains in motor performance and mental concentration during mental practice. [Conclusion] The results suggested that limited mental practice for individuals with poststroke hemiparesis may not improve motor performance. However, a higher degree of concentration during mental practice may improve motor performance.

A comparison of at-home walking and 10-meter walking test parameters of individuals with post-stroke hemiparesis.

[Purpose] The purpose of this study was to clarify the difference in gait parameters of at-home walking and the 10-meter walking test results of individuals with hemiparesis. [Subjects] A total of 14 hemiparetic stroke recovery patients participated in this study. Inclusion criteria were: living at home, the ability to walk independently, and demonstrated low extremity on recovery stages III-V on the Brunnstrom Approach. The average age of the subjects was 66 years. [Methods] We used video surveillance and the inked footprint technique to record usual walking speed and maximum speed patterns both in subjects' homes and during the 10-meter walking test. From these methods, walking speed, stride length, and step rate were calculated. [Results] While both usual and maximum walking speeds of the 10-meter walking test correlated with stride length and step rate, at-home walking speeds only significantly correlated with stride length. [Conclusion] Walking patterns of the 10-meter walking test are quantifiably distinct from those demonstrated in patients' homes, and this difference is mainly characterized by stride length. In order to enhance in-home walking ability, exercises that improve length of stride rather than step rate should be recommended.

The activation of apoptosis factor in hindlimb unloading-induced muscle atrophy under normal and low-temperature environmental conditions.

In order to identify the apoptosis-induced factors and apoptosis pathway in hindlimb unloading muscle atrophy, the reciprocal relationships between caspase-3 activation and factors related to mitochondria, other organelle pathways, oxidative stress and nitric oxide were investigated. Male Wistar rats were divided into four groups, two groups of hindlimb-unloaded rats were maintained under normal (25 degrees C) and low-temperature (10 degrees C) environmental conditions for a 3-week experimental period, plus two corresponding control groups. Active caspase-3-containing myofibers were observed in the hindlimb-unloaded rats in normal and low-temperature environments, but not in the control rats. In these caspase-3-containing fibers, DNA fragmentation, dystrophin breakdown, increased immunolabeling of mu-calpain, decreased cytochrome c, cathepsin-D effusion from the lysosomes and increased lipid peroxidation were observed, while no changes in active caspase-12, eNOS or nNOS immunolabeling were seen. Furthermore, although caspase-3 activation was observed in type-I fibers, caspase-12 labeling was observed in fibers of the hybrid type. These results show that the apoptosis observed in hindlimb unloading-induced muscle atrophy is caused by activation of the caspase cascade via the lysosome pathway. Moreover, the results suggest that caspase-12 does not activate caspase-3 due to differences in the cell differentiation or the apoptosis-inducing stimulation.