Insulin action and long-term electrically induced training in individuals with spinal cord injuries

Purpose: Individuals with spinal cord injuries (SCI) have an increased prev alence of insulin resistance and type 2 diabetes mellitus. In able-bodied i ndividuals, training with large muscle groups increases insulin sensitivity and may prevent type 2 diabetes mellitus. However, individuals with SCI ca nnot voluntarily recruit major muscle groups, but by functional electrical stimulation (FES) they can now perform ergometer bicycle training. Methods: Ten subjects with SCI (35 +/- 2 yr (mean +/- SE), 73 +/- 5 kg, level of le sion C6-Th4, time since injury: 12 +/- 2 yr) performed 1 yr of FES cycling (30 min.d(-1). 3 d.wk(-1) (intensive training)). Seven subjects continued 6 months with reduced training (1 d.wk(-1) (reduced training)). A sequential , hyperinsulinemic (50 mU.min(-1).m(-2) ( step 1) and 480 mU.min(-1).m(-2) (step 2)), euglycemic clamp, an oral glucose tolerance test (OGTT), and det ermination of GLUT 4 transporter protein in muscle biopsies were performed before and after training. Results: Insulin-stimulated glucose uptake rates increased after intensive training (from 4.9 +/- 0.5 mg.min(-1).kg(-1) to 6.2 +/- 0.6 mg.min(-1).kg(-1) (P < 0.008) (step 1) and from 9.0 +/- 0.8 mg. min(-1).kg(-1) to 10.6 0.8 mg.min.kg(-1) (P = 0. 103) (step 2)). With the r eduction in training. insulin sensitivity decreased to a similar level as b efore training (P > 0,05). GLUT 4 increased by 105% after intense training and decreased again with the training reduction. The subjects had impaired glucose tolerance before and after training, and neither glucose tolerance nor insulin responses to OGTT were significantly altered by training. Concl usions: Electrically induced bicycle training, performed three times per we ek increases insulin sensitivity and GLUT 4 content in skeletal muscle in s ubjects with SCI. A reduction in training to once per week is not sufficien t to maintain these effects. FES training may have a role in the prevention of the insulin resistance syndrome in persons with SCI.