The role of physical activity in the prevention of diabetes mellitus is of utmost importance. According to the Center for Disease Control and Prevention, nearly 10 percent of Americans are affected by diabetes. Furthermore, the American Diabetes Association purported that approximately 80 million Americans are pre-diabetic. Insulin resistance in skeletal muscle is considered to be the primary defect in type 2 diabetes1. Studies have shown that individuals who engage in resistance training programs were able to lower glucose levels effectively2 and increase insulin sensitivity3.Click here for more information
Effects of Strength Training on Diabetes
When compared to aerobic activities, resistance training has been shown to be a more effective intervention in terms of glucose and insulin control. A study published by Eriksson in the Journal of Hormone and Metabolism Research showed that a 3-month progressive resistance program consisting of two days a week circuit training was more effective in lowering glucose levels when compared to a cardio program2. These results were recently supported in Diabetology & Metabolic Syndrome4. Similarly a study by Ishii and colleagues in the Journal of Diabetes Care found that moderate-intensity, high volume training improved insulin sensitivity by 48%3. Therefore, it seems that resistance training programs elicit skeletal muscle adaptations that enhances glucose control.
Mechanisms – Why is Resistance Training so Effective?
Improvements in Glucose Transport-4 Recepetors (Glut-4) 5,6
You will find Glut-4 receptors on the wall of every muscle cell. Its function is to act like a door to allow glucose to pass from the bloodstream to the muscle. At rest, glut-4 does not function properly in diabetics, but during resistance exercise they function normally. Strength training increased protein content of GLUT4, insulin receptor sensitivity, protein kinase B-α/β, glycogen synthase (GS), and GS total activity; factors that increase insulin sensitivity.
Diagram demonstrating Glut-4 receptors site in the muscle and how it aids in glucose uptake
Increases in Adiponectin7
Adiponectin has been shown to increase glucose uptake by the cells. It is a hormone that regulates the secretion rate of glucose from the liver into the bloodstream. Decreases in adiponectin levels are therefore associated with insulin resistance. Performing Circuit resistance training 3x a week with 4 sets of 12 reps at 50-65% of 1 Repetition Maximal for 12 weeks was shown to significantly improve adiponection levels
Higher intensity exercises are known to rely more on muscle glycogen; increasing glycogen resynthesis, storage capacity, and promoting glucose uptake. Repeated muscle contractions have an effect on protein mechanism that increases insulin sensitivity.