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Abstract. The purpose of this study was to investigate the effects of weight bearing at varying intervals in suppressing the progression of disuse muscle atrophy, while setting the total daily weight bearing time constant. Disuse muscle atrophy was induced by 2-week hindlimb suspension. Thirty male Wistar rats ( weight : 215 ± 8 g ) were divided into 6 groups ( 5 rats/group ) : control (CON), suspension alone (SUS), two sessions of 30-minute weight bearing at intervals of 4, 8, and 12 hours during suspension, and one session of 60-minute weight bearing at intervals of 24 hours during suspension. Weight bearing was done each day during the daytime. Histochemical staining, followed by morphometrical analysis using NIH Image, demonstrated that the cross-sectional area of type I fiber in SUS was 44% of that in CON, while in the weight bearing groups ranged from 62 to 70%. The proportion of type I fibers was lower in SUS and tended to increase as the interval of weight bearing become longer, indicating the effects of weight bearing at intervals of 12 and 24 hours. For both types I and II, the distribution of muscle fiber size indicated that weight bearing at longer intervals was more effective in keeping the cross-sectional areas of muscle fibers closed to that in CON. In conclusion, when suppressing the progression of disuse atrophy of rat soleus muscle by weight bearing of one hour per day, the results suggest that the weight bearing intervals is important factor.

Prevention of disuse muscle atrophy is an important problem in physical therapy. Although several reports have been published concerning the effect of weight bearing on the prevention of disuse atrophy of lower extremity muscles, few basic clinical data are available. The present study was undertaken to examine differences in the progression of disuse muscle atrophy in terms of the time when weight bearing is started. The experimental materials consisted of the soleus muscles of 30 male Wistar rats (weight: 220 ± 6 g). The rats were divided into the control group (CON) and the experimental group, and disuse muscle atrophy caused by non-weight bearing was induced by hindlimb suspension for two weeks in the latter group. The experimental group was subdivided into four groups: no weight bearing permitted (SUS), and daily weight bearing permitted from 1, 4 and 7 days after the start of suspension (1-D, 4-D and 7-D). The relative weight of the soleus muscles did not differ for CON and 1-D or for 7-D and SUS. The mean cross-sectional area of type I fibers was 68% of that of CON for 1-D, 61% for 4-D, 52% for 7-D and 52% for SUS. This parameter showed significant differences any two groups, except for between 7-D and SUS. The results were regarded as normal in view of differences in the total time of weight bearing. The data also suggested that disuse muscle atrophy can be prevented quantitatively if weight bearing is initiated from the day following the start of suspension, and that early start of weight bearing is more effective for controlling atrophy progression.

Joint contractures after a long period of immobilization are a common problem for physical therapists. As for research on joint contracture, mainly histological and biochemical studies have been performed. In the biochemical study of joint contracture, it is considered that changes in the collagen fiber in the soft tissue around the joint are related to joint contracture and that an increase in collagen in the tissue and changes in the cross-link formed in the collagen fiber lead to a decrease in tissue flexibility 1)2) .This cross-link contributes as an important factor to collagen fiber solubility. It is generally recognized that the collagen fiber which is solubilized by neutral salt contains a small quantity of cross-link, and that the collagen fiber which contains an intramolecular cross-link is primarily solubilized by acid. Also, the collagen fiber which contains an Abstract. We have been studying mainly the changes in collagen fiber solubility with respect to its influence on immobilization of the soleus muscle and Achilles tendon of rats. We decided to investigate also the change of the collagen fiber solubility in the gastrocnemius muscle which, like the soleus muscle, is assumed to influence the range of motion of the ankle joints. The purpose of this study, therefore, was to investigate the effects of a 7-week immobilization on the solubility of the gastrocnemius muscle and soleus muscle collagen fiber of rats. The results were that in a 7-week immobilization period, hydroxyproline concentration in tissue was increased and salt and pepsin soluble collagen was decreased in both the soleus and the gastrocnemius muscles. The results suggest an increase in the collagen concentration in tissue and an increase in the intermolecular cross-link with a stronger molecular structure. As far as the amount of collagen and solubility were concerned, the immobilization had a similar influence on the collagen fiber in both muscles. Key words: immobilization, collagen solubility, soleus and gastrocnemius muscles (J Jpn Phy Ther Assoc 2: 25-29, 1999) intermolecular cross-link becomes insoluble collagen which is not solubilized by either salt or acid solution.We have been mainly studying the changes in collagen fiber solubility with regard to its effect on immobilization of the soleus muscle and Achilles tendon of rats [3][4][5] . We reported 3) that the rate of collagen in tissue was increased significantly by a 3-week immobilization, and that salt soluble collagen and the pepsin solubilization rate of insoluble collagen was decreased significantly by a 3-week immobilization. In view of this, we suggested that there was an increase in the amount of collagen in tissue, abnormal changes in cross-link, and the possibility of a cross-link having developed with a stronger molecular structure 3)5) .On the other hand, with regard to the Achilles tendon, we reported 4) that the amount of collagen in tissue had not changed significantly after a 7-week immobilization, and the change in collagen solubility was less than that in ...

P ロ rpose ： In order to obtain relevant information for optimizing the performance of air mat ・ tresses for elderly individuals ， the study was designed to ， 1)Establish the relat 童 onship between the internal air pressure of the mattress and interface pressure wh 童 le the subjects were at different positions ． 2)To see whether healthy young individuals could serve as valld controls for this kind of evaluation ． Subjects ； The sublects co 蝨 sisted of 8 elderly bed ・ bOund individuals withah 量 story of pressure ulcer and 8 healthy females agod 20 years ． The interface pressure was measured by a con − tact pressure distribution measurement device mads by NEC ・ Sanei Co ． with subjects in either asupine or lateral recumbent position and the head of the Gatch − bed raised to 30 ， 450r 70 degrees． The maximum interface pressure at the internal pressure setting of l80r 36 mmHg was compared to the known pressure level associated with ulcer formation ， This was performed while the subject was lying ln a range of different positions ． The cellular type aiternating Pressure mattress was used in the study ． Res 腿 蓋 ts l 1 ) When the Gatch − bed was set at any ang 】 e reductlon of internal air pressure effectively achieved more uniform pressure distribution at the tissue interface for the elderly ， although Gatch − bed ang 】 es with a head elevation greater than 45 degrees were associated with the