Improvements In Plantarflexor Size And Function Following Rehabilitation After Lower Leg Injury

Abstract

Rehabilitation following injury and immobilization has a positive impact on muscle recovery. However, muscle atrophy and weakness and recover at different rates following immobilization. PURPOSE: To determine changes in plantarflexor (PF) muscle size and strength in subjects with lower extremity fractures, who underwent immobilization followed by a structured rehabilitation program. METHODS: Subjects included 10 males and 7 females [(20-46 yrs, BMI 24.8± 4.0 (mean ± std)] who sustained lower leg fractures and were immobilized for at least 4 weeks. Subjects participated in a 6-week rehabilitation program that began immediately following immobilization. The program consisted of progressive resistance training of the ankle PFs and progressive treadmill walking. Measurements were taken immediately prior to and following rehabilitation. T1-weighted, axial images of the lower leg were obtained from MRI (1.5T or 3T) and were used to determine the maximal cross-sectional area (CSA) of the PFs. Maximal voluntary isometric torque of the ankle PFs was measured on a Biodex dynamometer. Peak torque and Time to Peak Torque were analyzed using Acknowledge software. RESULTS: Subjects experienced 23% improvement in PF CSA values after rehabilitation in the injured limb compared to a 4% increase in the noninjured limb. Muscle strength measures also showed an improvement, with a 30% increase in peak torque in the injured limb and 14% in the noninjured limb. Time to Peak Torque showed similar results with a 20% improvement in the involved limb and 15% improvement in the uninvolved limb. CONCLUSIONS: Following a period of immobilization and rehabilitation, muscle size tends to recover to a lesser extent than muscle strength. Improvements in muscle size are observed in the injured limb, whereas substantial muscle strength gains are seen in both the injured and uninjured limbs, which may indicate an improvement in neuromuscular recruitment of the PFs following rehabilitation.