Resistance Training and Type 2 Diabetes

Diabetes is a disease that involves the body’s ability to properly clear glucose from the blood stream. When excess glucose, or blood sugar, builds up in the body serious problems can result. These problems affect kidneys, eyes, nerves gums and teeth. A very serious problem that can develop is cardiovascular disease. A diabetic’s risk for heart attack is the same as a person who has already had an attack. (1) This risk applies to both men and women. To moderate this risk it important to keep blood pressure and blood fat levels under control.

The regulation of blood glucose requires a delicate balance between several signaling proteins that bring glucose in and out of the cell. The hormone insulin begins a cascade of events that lead to entry of blood glucose into the cell. If the cascade is inhibited at any of the many steps the glucose clearance rate is slowed. This causes a rise in blood sugar levels that is so detrimental to human health.

One glucose transport protein that has been looked at is called GLUT4. This protein is located inside the cell. With the stimulation of insulin through a series of steps, GLUT4 is sent (translocated) to the cell membrane to carry glucose molecules into the cell. If the cell does not have a high ratio of these transporters then the cell may decrease the number of receptor sites for insulin and become insulin intolerant. This condition (also known as insulin resistance) is a precursor to diabetes type 2. Diabetes type 2 is characterized by insulin resistance and a relative decrease in the effectiveness of insulin. There is also a genetic component with type 2, however, lifestyle choices can inhibit or slow the development of the disease. (2)

Epidemiologically type 2 diabetes is a major health concern world -wide. Type 2 diabetes was rarely seen in children but, now it is seen world -wide in both children and adults (mostly in low and middle income countries). The World Health Organization estimates that in 2005 over 1.1 million people died of the disease. There is a projection of a 50% increase in deaths in the next ten years in low to middle income countries, and in upper income countries an 80% increase between 2006-2015.(3).

Exercise is a common method used to manage diabetes type 2. Much of the research on type 2 diabetes and exercise has been concerned with aerobic exercise. Walking is the easiest aerobic exercise to perform. Unfortunately, many overweight individuals find walking to be difficult on joints and many abandon the activity. Resistance training (RT) is a good alternative. Research has shown that RT can help maintain glucose clearance rates.

Muscle is one of the main repositories of blood sugar. (The liver is the other one.) There are two main muscle fiber types; slow twitch type one (T1) and fast twitch type two (T2). Both muscle types use a mix of glucose and fats, however, type one fibers have the ability to use more oxygen and thus tend towards fat as a fuel source. Type 2 fibers are the muscles that are used to initiate movements and fast actions. Their main fuel mix is predominately glucose. How does this affect blood sugar levels in a type 2 diabetic?

Research has shown that overweight individuals have different ratios of muscle fiber types than lean individuals. Tanner et al in 2002 determined that obese women possessed lower levels of T1 (slow twitch oxidative) fibers than lean. This means that their levels of T2 fibers (fast twitch, glycolytic) were relatively higher. (The authors speculate that this may be why it is difficult for obese individuals to lose weight and to keep it off. If you have a lower percentage of fat burning muscle fibers then it can be difficult to burn enough calories through aerobic exercise to lose weight and to keep it off.)(4) Michael Gaster et al found that in overweight and obese individuals there is a lower ratio of GLUT4 in T1 muscle than in lean individuals’ T1 muscle. This means that blood sugar clearance is much lower. In type 2 diabetics the GLUT4 ratio is even lower in T1 muscle than in overweight non-diabetics. (5) (Remember the process that blood sugar needs to enter into the muscle cells? Insulin attaches to the cell receptor and causes a cascade of actions that result in the glucose being transported into the cell via the transporter called GLUT4. These transporters have to be present in the cell at a certain ratio or level. )

What does this mean? It means that those who are diabetic and overweight may have difficulty using aerobic exercise as a means to weight loss and maintaining blood glucose levels. But, remember those type 2 muscle fibers? There are quite a few studies that have shown that resistance training can improve glucose regulation. The common belief is that the increase in lean mass was the reason for this improvement. This may not be the case.

Ben Yaspelkis and his associates found that in rat skeletal muscle GLUT4 signaling was improved with resistance training. This is due to an increase in signaling proteins and GLUT4 levels in T2 muscle fibers. Two sets of rats were placed on two exercise protocols; 1. aerobic exercise and 2. resistance exercise. Aerobic rats ran on a motorized treadmill for 12 weeks three times per week. Resistance rats were placed on a RT program of three sets of 10 repetitions with 75% of their one repetition maximum three times per week for 12 weeks. (He made an ingenious rat squat machine.)

Both sets of rats had improved glucose clearance. The aerobic rats showed improvements in lower leg muscle used for running. The RT rats showed better glucose uptake in the upper leg used for squatting. (The resistance trained rats had glucose transport improvements without an increase in muscle size.) The results are not surprising since there is quite a body of literature supporting aerobic exercise as an effective way to improve glucose clearance rates in both type2 diabetics and healthy populations. There is a smaller number of studies that show RT to have a positive effect on clearance rates and those studies that have been done have not looked extensively at the mechanism for improvement. Yaspelkis et al have shown that the improvements in clearance is due to more effective activation of the insulin stimulated signaling cascade in resistance trained muscle. (6)

Insulin sensitivity in older Hispanic men has been found to be improved after 16 weeks of resistance training. Naomi Brooks et al report that after 35 minutes three days per week of 16 weeks of resistance training that there were improvements in muscle quality, whole body insulin sensitivity, decreased inflammation, and better metabolic control as a result of the improvements. (7) Dunstan et al also found that in overweight men and women aged 60-80 years high intensity weight training plus moderate weight loss is effective in improving blood sugar control. (8) Resistance training can be an effective alternative to aerobic exercise for diabetes type 2 patients especially for older individuals.

Patients with complications from diabetes type 2 such as, peripheral neurological problems, cardiovascular disease, retinopathy, autonomic neuropathy (affecting the nerves to the heart), and high blood pressure need to use lower intensity resistance training. The American College of Sports Medicine recommends that blood glucose levels be checked prior to and after exercise. If glucose levels are >250 ml/dl then exercise needs to be postponed until levels are normalized. If glucose levels are <100 ml/dl then a snack should be eaten prior (about 10-20 grams of easily absorbed carbohydrate). Good shoes are mandatory for a diabetic due to circulation issues. Feet should be checked regularly and kept clean. A diabetic patient should exercise with a partner or under supervision in case of an emergency. (9)

Check with your physician before undertaking an exercise program.


1. http://www.diabetes.niddk.nih.gov/dm/pubs/type1and2/what.htm
2. http://www.healthinsite.gov.au/topics/Types_of_Diabetes
3. http://www.who.int/features/chronic_disease/en/index.html
4. Tanner, C.J., Barakat, H.A., Dohm,G.L., Pories, W.J., MacDonald, K.G., Cunningham, P.R., Swanson, M.S., and Houmard, J.A. “Muscle fiber type is associated with obesity and weight loss.” Am. J. Physiol Endocrinol Metab, 282:E1191-E1196, 1002.
5. Gaster, M., Stacher,P., Beck-Nielson, H., Schrader H.D., and Handberg, A. “Glut4 is reduced in slow fibers of type 2 diabetic patients.” Diabetes, June 2001, vol 50.
6. Yaspelkis, Ben. “Resistance training improves insulin signaling and action in skeletal muscle.” Exer. Sport Sci. Rev., Vol. 43, pp. 42-46, 2006.
7. Brooks,N., Layne, J.E., Gordon, P.T., Roubenoff, R., Nelson, M.E., Castaneda-Scappa, C. “Strength training improves muscle quality and insulin sensitivity in Hispanic older adults with type 2 diabetes.” Int. J Med Sci, 4(1):19-27, 2007.
8. Dunstan, D.W., Daly, R.M., Owen, N., Jolley, D., de Courten, M., Shaw, J., and Zimmet, P. “High intensity resistance training improves glycemic control in older patients with type 2 diabetes.” Diabetes Care, 25(10): 1729-1736, 2002.
9. ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescription, 5th ed. American College of Sports Medicine, 2006