The purpose of this study was to investigate the effect of reloading on atrophied muscle and the time course of hypertrophy and regeneration. Forty-nine male Wistar rats were randomly assigned to groups for hindlimb suspension (HS), hindlimb suspension and reloading (R), or control (C0). Rats in the HS group were suspended for 14 days. Rats in the R group were randomly divided into five subgroups for different post-hindlimb-suspension recovery times. Briefly, each subgroup was suspended for 14 days and given 1 day of reloading (R1), 3 days of reloading (R3), 7 days of reloading (R7), 10 days of reloading (R10), or 14 days of reloading (R14). Myonuclear numbers were significantly decreased in the groups with hindlimb suspension and 1 day and 3 days of reloading compared with that in the control group. We focused on the processes of change of mean myofiber cross-sectional area and myonuclear domain size; the degrees of increase of both indexes were limited until 3 days of reloading, and significantly increased after 7 days of reloading. An important finding of the current study was that the processes of muscle hypertrophy and regeneration did not show uniform change. In addition, there were differences in the ratio of increase among the stages of hypertrophy and regeneration. Therefore, consideration of the duration and method of physiotherapeutic intervention for atrophied muscle on the basis of the process of hypertrophy and regeneration is needed to provide more effective physiotherapy.

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The purpose of this study was to determine the influence of passive stretching on inhibition of disuse atrophy and hemodynamics among longitudinal regions of the rat soleus muscle. Disuse muscle atrophy was induced by hindlimb suspension for two weeks. Muscle blood flow was evaluated using thallium-201 (²⁰¹Tl) which is a radiotracer that has been reported to be useful to assess blood perfusion in skeletal muscle. Thirty-nine male Wistar rats were divided randomly into 5 groups: control (C: n = 10), a group with hindlimb suspension (HS: n = 7), a group with hindlimb suspension and stretching (ST: n = 7), a group receiving only a single session of stretching after the hindlimb suspension period that was killed just after stretching (HSB: n = 7), and a group receiving only a single session of stretching hindlimb suspension and stretching period that was killed just after stretching (STB: n = 8). From the results of the cross-sectional area (CSA) and the capillary-to-fiber ratio (C/F), muscle atrophy and inhibition of atrophy were shown more in proximal than in distal regions of experimental groups. These results suggest that the alterations of the C/F and CSA were different among muscle regions in experimental groups. These differences may depend on the level of stretching. Moreover, alteration of blood flow resulting from alteration of the mechanical environment had little influence on muscle atrophy or inhibition of atrophy.

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Background: Strength of the trunk muscles is a key component of motor control, but it declines easily with the process of aging and/or disuse. Objectives: To investigate the effects of surface electrical stimulation (ES) to the abdominal muscles and the motor performance for care-needing elderly. Design: Controlled trial. Participants: Twenty-one elderly people (60-90 years) with care-needing, who were admitted to a nursing home or hospital for daily care and their score of Barthel Index had been stable from 55.3 ± 19.4 to 55.3 ± 19.8 during 3 months before intervention. Intervention: Common physical/occupational therapy was performed for all of the subjects during the study period. ES was applied to the abdomen of 15 subjects (ES group) twice a day for 8 weeks. Measurements: Functional measurements were performed before and after beginning of the study with some parameters as follows: grip strength; movement time for sitting up (MSU); maximum walking speed (WS). Results: No significant differences between two groups were noted for characteristics at baseline. In the ES group, MSU (from 21.1 ± 21.4 to 10.4 ± 8.3 sec) significantly improved (p < 0.05) after 8weeks. WS (from 17.7 ± 12.1 to 24.3 ± 15.3 m/min) were also improved (p < 0.05) after 8 weeks. Limitations: A limitation of this study was the small sample size. Conclusions: ES to the abdominal area has the potential to improve motor function in the care-needing elderly through reinforcement of the abdominal muscles.

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