Altered leverage around the ankle in people with diabetes: A natural strategy to modify the muscular contribution during walking?

Highlights

• People with diabetes show a reduced external moment arm and larger effective mechanical advantage at the ankle compared to controls and independent of walking speed.

• This altered leverage around the ankle in people with diabetes highlights a novel mechanism through which they can reduce the joint moment at the ankle despite the matching of walking speed between groups.

• The altered leverage at the ankle in people with diabetes results in a lower contractile force required from the plantarflexor muscles, lowering the muscular demands of walking.

Abstract

Diabetes patients display gait alterations compared to controls including a higher metabolic cost of walking. This study aimed to investigate whether differences in external moment arm (ExtMA) and effective mechanical advantage (EMA) at the ankle in diabetes patients could partly explain the increased cost of walking compared to controls. Thirty one non-diabetic controls (Ctrl); 22 diabetes patients without peripheral neuropathy (DM) and 14 patients with moderate/severe diabetic peripheral neuropathy (DPN) underwent gait analysis using a motion analysis system and force plates. The internal Achilles tendon moment arm length was determined using magnetic resonance imaging during weight-bearing and ExtMA was calculated using gait analysis. A greater value (P < 0.01) for the EMA at the ankle was found in the DPN (0.488) and DM (0.46) groups compared to Ctrl (0.448). The increased EMA was mainly caused by a smaller ExtMA in the DPN (9.63 cm; P < 0.01) and DM (10.31 cm) groups compared to Ctrl (10.42 cm) These findings indicate that the ankle plantarflexor muscles would need to generate lower forces to overcome the external resistance during walking compared to controls. Our findings do not explain the previously observedhigher metabolic cost of walking in the DM and DPN groups, but uncover a new mechanism through which patients with diabetes and particularly those with DPN reduce the joint moment at the ankle during walking: by applying the ground reaction force more proximally on the foot, or at an angle directed more towards the ankle, thereby increasing the EMA and reducing the ankle joint moment.