Exercise as it relates to Disease/Resistance Training and Insulin Sensitivity in Type II Diabetics
What is Insulin Sensitivity?
When the digestive system breaks down food to produce glucose, it is absorbed into the blood stream and the body’s blood glucose level (BGL) rises. As the BGL rises, the pancreas releases insulin to help the uptake of glucose by the cells to use as energy. In a non-diabetic, normal levels of the hormone insulin are released after a meal to help restore the blood glucose levels to normal as the tissues respond by absorbing glucose, storing it as glycogen. In an insulin resistant person, this process breaks down and the body fails to use the secreted insulin effectively because the cells do not respond adequately to the presence of insulin. . As a result, more insulin is required to reduce the BGL causing the pancreas to work harder to keep up with the demand. Eventually the pancreas cannot keep up with the demands and begins to fail, causing the BGL to rise exponentially.
What is Type II Diabetes?
Non insulin dependent diabetes mellitus (NIDDM), or type II diabetes is a metabolic disease in which the body produces insulin, but can’t use it efficiently because of insulin resistance. According to Diabetes Australia, 1.7 million Australians have diabetes, and an estimated 2 million Australians are pre-diabetic. The exact cause of NIDDM is still unknown but it is believed to be caused by both genetic and environmental factors.
What is Resistance Exercise Training (RET)?
Resistance exercise training involves each effort being performed against an opposing force. It is used to develop strength and size of skeletal muscles and is achieved by progressively overloading the musculoskeletal system so it gets stronger.
How does Resistance Exercise improve Insulin Sensitivity?
The treatment goal in patients with Type II Diabetes is to achieve and maintain a relatively normal blood glucose level by increasing insulin sensitivity. Resistance exercise training is a therapeutic modality used to achieve this in the following ways:
- Body sensitivity to insulin is directly proportional to muscle mass and the decrease in insulin resistance is related to an increase in lean body mass, allowing more glucose to be cleared from the blood.
- Changes in the quality of muscles, not just the quantity of muscles improves skeletal muscle insulin sensitivity. A shift from Type IIb muscle fibres to more insulin sensitivity Type IIa muscle fibres decreases insulin resistance.
The results from a variety of studies indicate that changes in insulin sensitivity and the signalling pathway are related to adaptations at a cellular level. These include: an increase in the glucose transporter isoform (GLUT-4), protein kinase B content (a kinase involved in the insulin signalling pathway to glycogen synthase) and glycogen synthase activity. After resistance exercise training, research shows that less insulin is required by the patient to achieve the same lowering effect on blood glucose levels, suggesting that insulin sensitivity will improve. Resistance trained muscles show improvements in their ability to alter components of the insulin signalling pathway in skeletal muscles, having elevated rates of glucose transport and a decrease in insulin resistance.
Recommendations for Resistance Training
Resistance exercise training can elicit metabolic benefits like improved insulin sensitivity with low to moderate intensity, low volume programs. This is key to engaging sedentary individuals who might be reluctant to participate in strenuous activity. These benefits begin to manifest themselves in a short period of time and these quick results can serve as a motivator to continue training. For the elderly, frail or overweight, resistance training programs are excellent as they provide less risk of sustaining injuries. Prior to beginning a resistance exercise program, diabetic patients should undergo a medical evaluation by their health care professional to ensure that they are safe to participate and that the activities in their programs can be performed correctly to maximize benefits and minimize risk of injury.
The American College of Sports Medicine recommends that resistance training should be integrated into the exercise programs for adults with Type II Diabetes and the following guidelines should be considered: The frequency of exercise should be 2-4 times a week at an intensity of 50-80% of patients VO2 max, sessions should be 30–60 minutes long, 1-2 sets at the beginning of the program but as patient progresses increase to 3-4 and each set should consist of 10-15 repetitions.
Resistance exercise training programs should be progressive and individually designed for each patient. As the patient’s insulin sensitivity improves, modifications to exercise type and intensity should be made. Modifications can be made for severe cases and high risk patients. Lighter workloads, strategic eating before and during exercise, constant checking of blood glucose levels and knowing the warning signs of hypoglycemia (dizziness, anxiety, shaking) will help with exercise tolerance. Following basic exercise protocols for proper warm-up and cool-down are also essential, as well as wearing appropriate footwear, maintaining adequate hydration and avoiding exercising in extreme environments.
For further information regarding insulin sensitivity and resistance training in Type II Diabetics contact your health care professional or visit:
- National Diabetes Information Clearinghouse - http://diabetes.niddk.nih.gov
- Diabetes Australia - http://www.diabetesaustralia.com.au
- Progressive Resistance Training Improves Insulin Sensitivity in Older Men With Type 2 Diabetes -http://care.diabetesjournals.org/content/28/3/662.full
- Effective Exercise Modality to Reduce Insulin Resistance in Women With Type 2 Diabetes - http://care.diabetesjournals.org/content/26/11/2977.full
- Field, J. Insulin Resistance in Diabetes. Annual Review of Medicine. 1962; 13; 249-260.
- Diabetes Australia, 2008. http://www.diabetesvic.org.au/health-professionals/diabetes-facts, 20/11/2011.
- Yaspelkis, B. Resistance Training Improves Insulin Sensitivity and Action in Skeletal Muscles. American College of Sports Medicine. 2006; 34; 1; 42-46.
- Sigal, R, Wasserman D. Physical activity/exercise and type 2 diabetes. Diabetes Care. 2004; 27; 2518-2539.
- Eves, N, Plotnikoff, R. Resistance Training and Type 2 Diabetes: Considerations for implementation at the population level. Diabetes Care. 2006; 29; 8; 1933-1941
- Balady, G, Tresierras, M. Resistance Training in the Treatment of Diabetes and Obesity: mechanisms and outcomes. Journal of Cardiopulmonary Rehabilitation and Prevention. 2009; 29; 67-75.
- Krisan, A.D., D.E. Collins, A.M. Crain, C.C. Kwong, M.K. Singh, J.R. Bernard, and B.B. Yaspelkis III. Resistance training enhances compo- nents of the insulin signaling cascade in normal and high-fat-fed skeletal muscle. J. Appl. Physiol. 2004; 96:1691–1700.
- Castaneda, C., J.E. Layne, L. Munoz-Orians, P.L. Gordon, J. Walsmith, M. Foldvari, R. Roubenoff, K.L. Tucker, and M.E. Nelson. A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes. Diabetes Care 2002; 25:2335–2341.