Neuromuscular dysfunction in diabetes: Role of nerve impairment and training status

PURPOSE: To investigate the effect of diabetes, motor nerve impairment and training status on neuromuscular function by concurrent assessment of the torque-velocity relationship and muscle fibre conduction velocity (MFCV). METHODS: Four groups were studied (n=12 each): sedentary diabetic patients in the first (lower) and fourth (higher) quartile of motor nerve conduction velocity (D1 and D4, respectively), trained diabetic patients (TD) and non-diabetic sedentary control subjects (C). Maximal isometric and isokinetic contractions were assessed over a wide range of angular velocities for the elbow flexors (EF) and knee extensors (KE) to evaluate the torque-velocity relationship. Simultaneously, MFCV was estimated from surface electromyography of the vastus lateralis (VL) and biceps brachii (BB). RESULTS: Isometric strength was similar among groups. EF dynamic strength was reduced in diabetic patients at the higher contraction speeds. KE strength was lower in sedentary diabetic patients at all velocities considered, with significantly lower values in D1 than in D4 at 60, 90 and 120°·s, whereas it was similar between TD and C subjects, especially at low contraction velocities. At the VL, but not the BB, MFCV was lower in D1 and D4, as compared to TD and C, showing similar values. CONCLUSIONS: Muscle weakness in diabetes affects also the upper limb, though to a lower extent than the lower limb, is only partly related to motor nerve impairment, and is dependent on contraction velocity. Exercise training might counteract diabetes-induced alterations in muscle fibre contractile properties and MFCV.

PURPOSE: The purpose of this study was to investigate the effect of diabetes, motor nerve impairment, and training status on neuromuscular function by concurrent assessment of the torque-velocity relationship and muscle fiber conduction velocity (MFCV). METHODS: Four groups were studied (n = 12 each): sedentary patients with diabetes in the first (lower) and fourth (higher) quartile of motor nerve conduction velocity (D1 and D4, respectively), trained diabetic (TD) patients, and nondiabetic sedentary control (C) subjects. Maximal isometric and isokinetic contractions were assessed over a wide range of angular velocities for the elbow flexors and knee extensors to evaluate the torque-velocity relationship. Simultaneously, MFCV was estimated from surface electromyography of the vastus lateralis and biceps brachii. RESULTS: Isometric strength was similar among groups. The dynamic strength of elbow flexors was reduced in patients with diabetes at the higher contraction speeds. The strength of knee extensors was lower in sedentary patients with diabetes at all velocities considered, with significantly lower values in D1 than that in D4 at 60°, 90°, and 120°·s, whereas it was similar between TD and C subjects, especially at low contraction velocities. At the vastus lateralis, but not the biceps brachii, MFCV was lower in D1 and D4 as compared with TD and C subjects, showing similar values. CONCLUSIONS: Muscle weakness in diabetes affects also the upper limb, although to a lower extent than the lower limb, is only partly related to motor nerve impairment, and is dependent on contraction velocity. Exercise training might counteract diabetes-induced alterations in muscle fiber contractile properties and MFCV