Effects of prolonged stretching and thermotherapy on muscle contracture of immobilized rat soleus muscle

Abstract

[Purpose] We examined the effects of prolonged stretching and thermotherapy on muscle contracture of immobilized rat soleus muscles by determining ankle joint range of motion (ROM), collagen fibril arrangement in the endomysium and insoluble collagen content. [Methods] In the experimental group, bilateral ankle joints of each rat were fixed in full plantar flexion with plaster casts for four weeks. Then, the experimental group animals were randomly partitioned into five groups: 1) immobilization alone; and 2) spontaneous recovery, 3) prolonged stretching, 4) thermotherapy, and 5) prolonged stretching immediately following thermotherapy for 2 weeks after cast removal. Prolonged stretching of the soleus muscle (30 min/day) was conducted by maintaining the dorsiflexion position of the ankle joint. Thermotherapy consisted of immersion of bilateral hindlimbs (20 min/day) in hot water (42 °C). Under anesthesia, both treatments were performed six days per week during the two-week remobilization. [Results] Immobilization led to decreased ROM, collagen fibril movement in the endomysium and increased insoluble collagen. Prolonged stretching and the combination of stretching and thermotherapy accelerated amelioration of the ROM limitation and diminished collagen fibril movement. [Conclusion] Our findings suggest that while thermotherapy does not exert a specific effect on muscle contracture, prolonged stretching can promote recovery.