Detailed assessment of motor function in patients with type 2 diabetes (T2DM) is important to identify early sub-clinical deficits and to implement early interventions in order to limit the development of advanced pathology and improve their quality of life. Lower limb muscular dysfunction has been demonstrated in several studies in patients with diabetic neuropathy (DN). Vitamin D deficiency is very common in patients with T2DM, both in subjects with impaired glucose tolerance (IGT) and in healthy subjects. Vitamin D deficiency can cause reduction in muscle strength, size, walking speed, a disturbance in dynamic sway during walking and an increased risk of falls in healthy elderly subjects. This project aimed to investigate muscle function, structure and kinematic alterations during walking activity in subjects with IGT and patients with T2DM in relation to vitamin D deficiency and neuropathy.The work in thesis shows that diabetes is associated with reduced muscle strength and size of the lower extremities in patients with T2DM, and that is related to the severity of neuropathy but not vitamin D deficiency. Furthermore, small fibre neuropathy has been related to distal muscle weakness and increased dynamic medio-lateral sway during walking in subjects with IGT and patients with T2DM. Vitamin D deficiency has been related to muscle weakness in subjects with IGT but not to kinematic alterations during walking.