The recovery time required for rat joint contractures treated with joint fixation with unweighting of the hind limbs.

[Purpose] The purpose of this study was to investigate whether the recovery period of joint contractures differ between treatments with joint fixation with unweighting of the hind limbs and joint fixation alone. [Subjects and Methods] Twelve 10-week-old male Wistar rats were divided into a group with joint fixation of the right ankle joints in full plantar flexion for 1 week (F) and a group with joint fixation and hind limb suspension (FS). Thereafter, the rats were removed from the joint fixation and hind limb suspension for 2 weeks. The ankle dorsiflexion angles during the recovery process of the joint contractures were measured. [Results] The ankle dorsiflexion angles of the F group from the day joint fixation was removed to the seventh recovery day were significantly lower than the pre-experiment values. The ankle dorsiflexion angles of the FS group from the day joint fixation and hind limb suspension were removed to the 10th recovery day were significantly lower than the pre-experiment values. [Conclusion] We found that the period required for the recovery of joint contractures treated with joint fixation with unweighting of the hind limbs was longer than that with joint fixation alone.

Study on change of rat soleus extensibility caused by reduction in joint movement with unweighting of the hind limbs.

[Purpose] The purpose of this study was to investigate the change in soleus extensibility from a joint contracture caused by a reduction in joint movement with unweighted lower limbs and to interpret the results to aid in the treatment of human joint contractures. [Subjects and Methods] The subjects of this study were twenty-one 10-weeks-old male Wistar rats. Twenty-one rats were divided into one control (C) and two experimental groups. The first experimental group included fixed right ankle joints in full plantar flexion (F). The second experimental group's hind limbs were suspended and the right ankle joints were fixed in full plantar flexion (FS). The period of this study was one week. On the first and last day of this study, all of the rats' ankle dorsiflexion angles were measured. On the last day of this study, all of the rats' soleus extensibilities were measured. [Results] On the last day of this study, the ankle dorsiflexion angles and the soleus extensibility in the FS group were significantly more decreased than those of the F group. [Conclusion] It was shown that the skeletal muscle extensibility from joint contracture caused by reduction of joint movement with unweighted lower limbs was more markedly decreased than that from joint contracture caused by reduction of joint movement.

Effects of joint immobilization and hindlimb unloading on collagen fibers of soleus muscles in rats.

[Purpose] The purpose of this study was to determine whether collagen fibers cause a difference in a contracture resulting from a combination of joint fixation and hindlimb unloading as compared to joint fixation only. [Subjects and Methods] The subjects of this study were 21 female Wistar rats divided into 4 groups as follows: Control Group (CON, n=7); Joint Fixation Group (JF, n=7), Hindlimb Unloading Group (HU, n=7), Joint Fixation Plus Hindlimb Unloading Group (JF+HU, n=7). This study was conducted for 1-week. Ankle joint range of motion and positive areas of collagen using fluorescent stain were analyzed. [Results] Ankle joint range of motion in JF + HU showed an increase compared to that of JF. Positive areas of Type I collagen in JF+HU showed an increase as compared with that of JF. [Conclusion] The results of this study suggested that the difference in a contracture caused by only joint immobilization and by a combination of joint immobilization and hindlimb unloading were significantly associated with Type I collagen.

A study of the relationships of changes in pain and gait after tourniquet-induced ischemia-reperfusion in rats.

[Purpose] The purpose of this study was to determine the relationships of changes in pain and gait after ischemia reperfusion was induced by tourniquet in rats. [Subjects and Methods] The subjects were six ten-week-old male Wistar rats. Ischemia was induced in the left lower limbs of the experimental rats at a pressure of 300 mmHg for 90 minutes. Pain behavior evaluations were measured using the von Frey test in all the rats' hind limbs. A consistently increasing plantar stimulus was applied until the rats exhibited an escape behavior. For the evaluation of gait, a two-dimensional motion analysis system was used to measure the distance from the calcaneus to the floor (DCF) and toe extension angle (TEA) during gait. The evaluations were performed in the normal state, 3 hours after ischemia-reperfusion, and daily until 7 days after ischemia-reperfusion. [Results] Compared with the normal state, the means of the pain threshold showed a significant decrease until 4 days after ischemia. In addition, both TEA and DCF continued to show a significant decrease at 7 days after ischemia as compared with the normal state. [Conclusion] This study revealed that hyperalgesia occurs after ischemia-reperfusion, and recovery of hyperalgesia occurred earlier than gait dysfunction recovery.

Study on changes in skin extensibility during the development of joint contracture due to joint immobilization in rats.

[Purpose] The purpose of this study was to elucidate whether skin extensibility decreases when a contracture develops as a result of joint immobilization. [Subjects] This study was conducted on six female Wistar rats. [Methods] The rats were divided into two experimental groups. In the immobilized group, the right ankle joints were immobilized in complete plantar flexion by plaster casts for two weeks. In the control group, the left ankle joints had no intervention. On the final day, skin extensibility was determined from a length-tension curve by collecting skin from the posterior aspect of the ankle joint and using a tensile strength tester. [Results] Compared with the control group, the immobilized group showed a significant decrease in skin extensibility. [Conclusion] The results demonstrated that the extensibility of the skin itself decreases when joint contracture develops.

Effect of stretch on improvement of muscular contractures in rats.

[Purpose] The purpose of this study was to investigate how a stretching torque affects muscular contractures. [Subjects] The subjects of this study were 48 male Wistar rats. [Methods] Subjects were divided into 4 groups as follows: Group 1 was the control; Group 2 had muscles in continuous fixation; Group 3 had muscles stretched in the direction of dorsiflexion by a spring balancer set at a torque of 0.3N for a period of 30 minutes after continuous fixation; and Group 4 had muscles stretched in the direction of dorsiflexion by a spring balancer set at a torque of 3.0N for a period of 30 minutes after continuous fixation. Joint fixation periods were for 2 and 4-weeks. Ankle joint range of motion and soleus flexibility were analyzed. [Results] For the 2-week joint fixation, soleus flexibility in Group 4 showed an increase compared with that of Group 3. For both fixation periods, range of motion in Group 4 showed an increase compared with that of Group 3. [Conclusion] For both fixation periods, stretching improved joint range of motion. In the 2-week joint fixation, soleus flexibility improved. However, soleus flexibility did not improve in the 4-week joint fixation.

Aerobic interval exercise with an eccentric contraction induces muscular hypertrophy and augmentation of muscular strength in rats.

[Purpose] The purpose of this study was to examine whether an aerobic interval exercise using an eccentric contraction would result in skeletal muscular hypertrophy and augmentation of muscular strength in rats. [Subjects and Methods] Twenty-one female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The aerobic endurance exercise group ran for 90 min. The aerobic interval exercise group ran for a total of 90 minutes in 5 minute bouts separated by 2 minute rest periods. The exercise groups ran on a downhill treadmill incline, once every three days, for a total of twenty sessions. [Results] The muscle wet weights, the muscle fiber cross-section minor axes, and the tetanus tension results of the aerobic endurance and aerobic interval exercise groups were significantly larger than those of the control group. [Conclusion] These results indicate that aerobic interval exercise may be an effective method of inducing hypertrophy and augmenting muscular strength in skeletal muscle.

Preventive effects of antioxidants and exercise on muscle atrophy induced by ischemic reperfusion.

[Purpose] This study aimed to determine whether muscle atrophy induced by ischemic reperfusion injury in rats can be prevented by the administration of antioxidants and exercise. [Subjects] Rats were randomly divided into five groups: non-treated, ischemic, exercise, ascorbic acid and exercise, and tocopherol and exercise. [Methods] The relative weight ratio of the soleus muscle and the length of the soleus muscle fiber cross-section minor axis were used for the evaluation of muscle atrophy. Pain was assessed as the weight-bearing ratio of the ischemic side. A multiple comparison test and the paired t-test were used for the statistical analyses. [Results] Compared with the non-treated group, the relative weight ratios of the soleus muscle and the lengths of the soleus muscle fiber cross-section minor axis significantly decreased in the other groups. Excluding the non-treated group, the relative weight ratios of the soleus muscle were heaviest in the tocopherol and exercise group. Excluding the non-treated group, the lengths of the soleus muscle fiber cross-section minor axis were longest in the tocopherol and exercise group, followed by the ischemic, exercise, and ascorbic acid and exercise groups. The amount of antioxidant substances did not decrease on the weight-bearing ratio of the ischemic side. [Conclusion] In this study, using an experimental rat model, we confirmed that antioxidants and exercise effect muscle atrophy induced by ischemic reperfusion. The results show that muscle regeneration was facilitated by phagocytosis in the tocopherol and exercise group.

Induction of Muscle Hypertrophy in Rats through Low Intensity Eccentric Contraction.

[Purpose] The purpose of this study was to examine whether a low intensity exercise using an eccentric contraction would result in skeletal muscle hypertrophy in rats. [Subjects and Methods] Eighteen female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The level group ran on a treadmill on a 0° incline. The downhill group ran on a treadmill on a -16° incline. The two exercise groups ran on a treadmill at 16 m/min for 90 minutes, once every three days for a total of twenty sessions. [Results] The muscle wet weights, the relative weight ratios, and the muscle fiber cross-section minor axes of the downhill group were significantly larger than those of the control and level groups. There were no differences in the muscle wet weights, the relative weight ratios, and the muscle fiber cross-section minor axes between the control group and the level group. [Conclusion] The stimulation from the low intensity eccentric contraction may have produced enough mechanical stress to induce muscle hypertrophy without the over-stressing that might have produced muscle fiber damage. These results indicate that this technique may be an effective method of inducing hypertrophy in skeletal muscle.

Effect on blood pressure of daily lemon ingestion and walking.

Background. Recent studies suggest that the daily intake of lemon (Citrus limon) has a good effect on health, but this has not been confirmed in humans. In our previous studies, it was observed that people who are conscious of their health performed more lemon intake and exercise. An analysis that took this into account was required. Methodology. For 101 middle-aged women in an island area in Hiroshima, Japan, a record of lemon ingestion efforts and the number of steps walked was carried out for five months. The change rates (Δ%) of the physical measurements, blood test, blood pressure, and pulse wave measured value during the observation period were calculated, and correlations with lemon intake and the number of steps walked were considered. As a result, it was suggested that daily lemon intake and walking are effective for high blood pressure because both showed significant negative correlation to systolic blood pressure Δ%. Conclusions. As a result of multiple linear regression analysis, it was possible that lemon ingestion is involved more greatly with the blood citric acid concentration Δ% and the number of steps with blood pressure Δ%, and it was surmised that the number of steps and lemon ingestion are related to blood pressure improvement by different action mechanisms.

Effect of skin resection on the improvement of joint contractures in rats.

The effect of skin resection on joint contracture was determined by comparing the first measurement of range of motion after cast removal and the second measurement after the skin resection. This study aimed to verify that both the joint movement during the measurement and skin affect range of motion. [Subjects] Twelve female Wistar rats were used. [Methods] The right hind limb ankle of each rat was immobilized in complete plantar flexion in a cast. In the resection group (n = 6), the skin of the right hind limb ankle was removed surgically, but not in the non-resection group (n = 6). In the resection group, the first measurement of the dorsiflexion angle was obtained after the cast was removed, and the second measurement was obtained after skin resection. In the non-resection group, both measurements of the dorsiflexion angle were obtained soon after the cast was removed. [Results] Compared with the non-resection group, the resection group showed a significant increase between the first and second measurements of range of motion. [Conclusion] These results show that range of motion is substantially affected by skin, in addition to joint movement, during measurement.

Effect of an Intermittent Eight-hour Joint Fixation Period on Joint Contractures in Rats.

[Purpose] It has been shown that an eight-hour joint fixation daily (i.e. for the remaining 16 hours, rats were set free in the cage without joint fixation) for one week induces a joint contracture. The purpose of this study was to investigate the difference between an 8 hours continuous joint fixation and an 8 hours intermittent joint fixation per day (two 4 hours joint fixations) in the development of joint contractures in rats. [Subjects and Methods] The subjects of this study were 34 Wistar rats. On the first day, all of the rats' right ankle dorsiflexion angles were measured. The right hind limbs of all the rats were fixed in plantar flexion, and then the rats were divided into three groups as follows: Group 1 was in continuous fixation for 24 hours a day; Group 2 was in continuous fixation for 8 hours a day; Group 3 was in intermittent fixation for 8 hours a day. The fixation was performed daily for seven consecutive days. On the last day, ankle dorsiflexion angles of all the rats were measured after the casts had been removed. [Results] The development of joint contractures was statistically significant for Groups 1 and 2. [Conclusion] Our results indicate that 8 hours a day of continuous fixation induces a joint contracture, but 8 hours a day of intermittent fixation does not.

Evaluation of the Lactate Threshold during Downhill Running in Rats.

[Purpose] The purpose of the present study was to investigate if lactate thresholds in rats could be accurately determined during downhill running in rats. [Subjects] Twenty-four female Wistar rats were used in this study. Rats were randomly divided into two groups: the level running group and downhill running group. [Methods] Catheters were inserted into the right external jugular veins of the rats. Two days after the operation, the rats performed incremental exercise tests. The level running group ran on a treadmill at a 0° incline; the downhill running group ran on a treadmill at a -16° incline. The lactate threshold was determined using the 2-line combination that minimizes the total sum of squares for fitting all data. [Results] Maximal running speeds and running speeds at the lactate threshold for the downhill running group were significantly higher than those for the level running group. [Conclusion] In this study, it was possible to accurately determine the lactate threshold during downhill running. These findings suggest that when the treadmill speed is the same, downhill running can be done at lower metabolic intensity than level running.

[Effect of variation of lemon intake and walking in daily life on various indicators of muscle mass and blood biochemistry in menopausal middle-aged and elderly women].

OBJECTIVES: We examined the factors considered to change body composition and blood biochemistry indicators in menopausal middle-aged and elderly women. These changes result from exercise by walking as part of their daily activities and lemon consumption by women who live on the small islands of the Seto Inland Sea, Japan's largest citrus fruit (lemon)-producing region. METHODS: Between September 2011 and March 2012, we recorded the daily lemon consumption and the number of steps taken by 101 middle-aged and elderly female lemon farmers. We also measured their body dimensions, body compositions, and blood pressure pulse wave velocity and conducted blood tests before and after the survey period. The results before and after the survey period were compared by the t-test and associations were determined on the basis of Pearson's correlation coefficient. Covariance structural analysis was carried out to determine causal associations. RESULTS: From the results of covariance structure analysis, lemon intake did not have a direct impact on each item examined. The third item, i.e., "the factors related to arteriosclerosis," was affected indirectly via citric acid and fatigue, and anticoagulation was shown. The fourth item, i.e., "the factors related to maintenance of muscle mass," which is affected by menopausal years and the change in walking speed, was shown to be associated with the second item, i.e., "the factors related to lipid metabolism." Menopausal years affected the first, third and fourth items. CONCLUSIONS: Lemon intake did not have a direct impact on each item. Lemon has been shown to indirectly affect the third item through citric acid. Walking affected the second item, the level of total cholesterol, such as HDL cholesterol, through the fourth item. The importance of providing services that lead to sustained physical activity and a well-balanced metabolism between lipids and carbohydrates has been shown.