According to the American College of Sports Medicine's Position Stance from 2010, diabetes is a rapidly spreading epidemic across the country, with an estimated 24 million Americans currently battling the disease. Diabetes is a class of conditions characterized by chronically high blood sugar levels. Type 2 diabetes is a specific form of the disease in which your cells become less responsive to the hormone insulin, a molecule that regulates the storage of blood glucose. Through the development of what is known as insulin resistance, Type 2 diabetics are unable to properly control blood sugar levels and require strict glucose control with either lifestyle changes or medication. Type 2 diabetes leads to premature mortality and morbidity because of increased risk of cardiovascular disease, eye damage, kidney disease and loss of sensation in the extremities. Regular physical activity may delay or even prevent diabetes, as well as these complications.
Acute Effects of Exercise
At rest, insulin is required for glucose to enter your cells. Muscle contractions during exercise act to stimulate glucose transport though a separate, insulin-independent mechanism. Therefore, even if you have Type 2 diabetes, the ability of your muscle to take up glucose during exercise is completely normal. Thus, exercise helps control blood glucose levels in diabetics without requiring insulin. Additionally, acute exercise improves the action of insulin in the short term. Physical activity of any intensity shows improved insulin sensitivity through increased uptake of blood glucose by muscle cells at rest. In fact, more prolonged, intense exercise enhances insulin efficacy for up to 72 hours afterward.
Chronic Effects of Exercise
Long-term exercise programs reverse symptoms of diabetes by enhancing the ability of muscle cells to respond to insulin. By increasing glucose transporters and insulin signaling molecules, skeletal muscle is able to increase uptake of glucose, improving blood glucose control. According to the American College of Sports Medicine, resistance training twice per week for 16 weeks in older men with Type 2 diabetes showed a 46.3 percent increase in the activity of insulin and a 7.1 percent reduction in blood glucose levels. This effect may be mediated by increased mass of muscular tissue capable of taking up blood glucose. The position statement from the ACSM concludes that long-term aerobic and resistance training improve insulin efficacy and decrease blood glucose.
Role in Prevention of Type 2 Diabetes
Aerobic exercise is a well-established approach to diabetes prevention and management, often showing improvement in insulin sensitivity after one week of training. According to the Da Qing study in China, even small increases in exercise reduce the risk of diabetes by 46 percent. These modest changes in physical activity may range from 20 minutes of mild exercise to five minutes of very strenuous exercise once to twice per day. The ACSM concludes that at least 2.5 hours of moderate exercise per day can prevent Type 2 diabetes onset in adults.
Applications in Treatment
Although many people with Type 2 diabetes are capable of taking on a moderate exercise routine, some with a long history of sedentary lifestyle should consider having an evaluation by a physician before beginning exercise. Many of the complications of diabetes predispose these people to injury during exercise. Conditions such as retinal disease may produce problems with vision and may complicate exercise. Similarly, peripheral neuropathy, or loss of sensation in the extremities, may make simple exercises such as brisk walking difficult. The ACSM recommends elderly, sedentary people to schedule a pre-exercise evaluation with their physician to rule out these conditions or make the appropriate adaptations to avoid injury during exercise.
