Muscle lengthening and structural changes in the muscle-tendon complex of triceps surae after 1 year of rehabilitation including a daily self-stretch program in patients with chronic hemiparesis

Abstract

To explore changes in muscle architectural parameters of the muscle-tendon unit of soleus and medial gastrocnemius (GM) in patients with chronic hemiparesis, after 1 year of rehabilitation. In this prospective study, 20 chronic hemiparetic patients (8 W, mean age: 56 [12], time since lesion 9 [8]) were evaluated. Muscle architectural parameters including muscle fascicle length, pennation angle, thickness, tendon and muscle belly lengths were evaluated in vivo using ultrasonography in passive condition (verified by electromyographic recording) in a seated patient with ankle, knee and hip on the paretic side at 90°. Following the biomechanical analysis, each patient benefited from the Five Step Assessment (FSA), involving the measure of XV1, angle of arrest at slow and strong stretch, which estimates soft tissue extensibility around each muscle. Four muscles of interest in the lower limb were selected for this measure: soleus (XV1Sol), medial gastro-soleus complex (XV1GSC), gluteus maximus (XV1GM) and rectus femoris (XV1RF). Biomechanical and clinical analyses were performed at the beginning and after 1 year of treatment. Two treatments were implemented: – conventional rehabilitation (50%); – guided Self-rehabilitation contract (GSC, 50%). Patients in the GSC group were prescribed a daily self-stretch program with static (> 10 min/muscle/day) and eccentric stretch. Changes in architectural parameters and clinical muscle extensibility of overall patients before and after 1 year of rehabilitation were analyzed (Student's). After 1 year, muscle fascicle length and thickness increased respectively by 6.1 mm (14.2%, P = 0.05), 1.8 mm (13.6%, P = 0.06) in soleus, and by 2.9 mm (9.1%, P = 0.04) and 1.7 mm (13.2%, P = 0.03) in MG. Muscle belly length of MG increased by 2.9 cm (17%, P = 0.0001) and its tendon length decreased by 0.82 cm (5%, P = 0.04). XV1GSC increased by 4.8° (3.3%, P = 0.07), XV1GM by 4.1° (3.3%, P = 0.0004) and XV1RF by 7.2° (6%, P = 0.02). Stretch of soleus and medial gastrocnemius practiced over the long term in patients with spastic hemiparesis allowed structural changes, increasing muscle fascicle length and thickness. Muscle belly length of medial gastrocnemius also increased significantly while its tendon length decreased, suggesting that the tendon may adapt its length to the muscle length changes.