Achilles tendon length changes during walking in long-term diabetes patients.

BACKGROUND: Diabetes leads to numerous side effects, including an increased density of collagen fibrils and thickening of the Achilles tendon. This may increase tissue stiffness and could affect stretch distribution between muscle and tendinous tissues during walking. The primary aim of this study was to examine stretch distribution between muscle and tendinous tissues in the medial gastrocnemius muscle-tendon unit in long-term diabetes patients and control subjects during walking.

METHODS: Achilles tendon length changes were investigated in 13 non-neuropathic diabetes patients and 12 controls, whilst walking at a self selected speed across a 10 m force platform. Electromyographic activity was recorded in the medial gastrocnemius, soleus and tibialis anterior muscles, goniometers were used to detect joint angle changes, and ultrasound was used to estimate tendon length changes.

FINDINGS: Achilles tendon length changes were attenuated in diabetes patients compared to controls, and were inversely correlated with diabetes duration (r=-0.628; P<0.05), as was ankle range of motion (r=-0.693; P<0.01). Tendon length changes were also independent of walking speed (r=-0.299; P=0.224) and age (r=0.115; P=0.721) in the diabetic group.

INTERPRETATION: Stretch distribution between muscle and tendon during walking is altered in diabetic patients, which could decrease walking efficiency, a factor that may be exacerbated with increasing diabetes duration. Diabetes-induced changes in mechanical tendon properties may be at least partly responsible for attenuated tendon length changes during walking in this patient group.