This study investigated the effects of wheel-running using the upper limbs following immobilization after inducing arthritis in the knees of rats. Forty male Wistar rats (aged 8 weeks) divided into four groups randomly: arthritis (AR), immobilization after arthritis (Im), wheel-running exercise with the upper limbs following immobilization after arthritis induction (Im+Ex) and sham arthritis induction (Con). The knee joints of the Im and Im+Ex groups were immobilized with a cast for 4 weeks. In the Im+Ex group, wheel-running exercise was administered for 60 min/day (5 times/week). The swelling and the pressure pain threshold (PPT) of the knee joint were evaluated for observing the condition of inflammatory symptoms in affected area, and the paw withdraw response (PWR) was evaluated for observing the condition of secondary hyperalgesia in distant area. Especially, in order to evaluate histological inflammation in the knee joint, the number of macrophage (CD68-positive cells) in the synovium was examined. The expression of calcitonin gene-related peptide (CGRP) in the spinal dorsal horn (L2-3 and L4-5) was examined to evaluate central sensitization. The Im+Ex group showed a significantly better recovery than the Im group in the swelling, PPTs, and PWRs. Additionally, CGRP expression of the spinal dorsal horn (L2-3 and L4-5) in the Im+Ex group was significantly decreased compared with the Im group. According to the results, upper limb exercise can decrease pain in the affected area, reduce hyperalgesia in distant areas, and suppress the central sensitization in the spinal dorsal horn by triggering exercise-induced hypoalgesia (EIH).

• MeSH
• Arthritis etiology   pathology   rehabilitation   MeSH
• Pain pathology   prevention & control   MeSH
• Upper Extremity physiology   MeSH
• Immobilization methods   MeSH
• Knee Joint physiopathology   MeSH
• Physical Conditioning, Animal methods   MeSH
• Rats MeSH
• Disease Models, Animal MeSH
• Rats, Wistar MeSH
• Spinal Cord Dorsal Horn pathology   MeSH
• Inflammation pathology   prevention & control   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

The effects of exercise on mechanical hyperalgesia, joint contracture, and muscle injury resulting from immobilization are not completely understood. This study aimed to investigate the effects of cyclic stretching on these parameters in a rat model of chronic post-cast pain (CPCP). Seventeen 8-week-old Wistar rats were randomly assigned to (1) control group, (2) immobilization (CPCP) group, or (3) immobilization and stretching exercise (CPCP+STR) group. In the CPCP and CPCP+STR groups, both hindlimbs of each rat were immobilized in full plantar flexion with a plaster cast for a 4-week period. In the CPCP+STR group, cyclic stretching exercise was performed 6 days/week for 2 weeks, beginning immediately after cast removal prior to reloading. Although mechanical hyperalgesia in the plantar skin and calf muscle, ankle joint contracture, and gastrocnemius muscle injury were observed in both immobilized groups, these changes were significantly less severe in the CPCP+STR group than in the CPCP group. These results clearly demonstrate the beneficial effect of cyclic stretching exercises on widespread mechanical hyperalgesia, joint contracture, and muscle injury in a rat model of CPCP.

• MeSH
• Chronic Pain etiology   pathology   rehabilitation   MeSH
• Hyperalgesia etiology   pathology   rehabilitation   MeSH
• Immobilization MeSH
• Physical Conditioning, Animal methods   MeSH
• Contracture etiology   pathology   rehabilitation   MeSH
• Muscle, Skeletal physiology   MeSH
• Rats MeSH
• Humans MeSH
• Disease Models, Animal MeSH
• Rats, Wistar MeSH
• Casts, Surgical MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH