Diabetes is a disease that is associated with the hormone insulin. Insulin is secreted by the pancreas following meals, and is required for uptake of glucose to be used in cells.

There are two types of diabetes: Type I and Type II. Type I diabetes is least common, and is due to the inability of the pancreas to produce insulin. This type of diabetes is usually present from birth, and requires insulin injections and/or pills. Type II is far more common, and therefore will be the focus of this paper.

Type II diabetes is also known as adult-onset diabetes, since most people develop this type as adults, as opposed to type I, which is acquired around birth. People with type II diabetes experience insulin resistance, and because of this their bodies are unable to respond to, and use, the available blood glucose. Glucose is an essential source of fuel for the body, as all carbohydrates are broken down into these basic building blocks. As a result, the cells of people with diabetes are essentially starving, and over time this can lead to eye, kidney, nerve, and heart damage. Diabetes is most common in African Americans, Latinos, Native Americans, and Asian Americans/Pacific Islanders, as well as the aged population, although this disease is not restricted to those populations. (1)

According to a major government study - the Diabetes Prevention Program (DPP) - regular exercise has been shown to delay, and in some cases, prevent the onset of Type II Diabetes. (2) In fact, in one study, the overall incidence of diabetes in people with impaired glucose tolerance was reduced by 58% with positive lifestyle changes. (3) These positive lifestyle changes focused on improving cardiovascular fitness and muscular strength, as well as physical activity in general.

“Large cohort studies have found that higher levels of habitual aerobic fitness, and/or physical activity, are associated with significantly lower subsequent cardiovascular and overall mortality, to a much greater extent than could be explained by glucose lowering alone.”(4) It is also known that exercise increases insulin sensitivity. Insulin sensitivity is a measure of how well the cells respond to and uses the available blood glucose. This is important for those with diabetes to consider as a way to manage this disease.

Before beginning any exercise program, it is important that a doctor be consulted. Considering which medications the patient is currently taking, and the proper types of exercise for that patient is essential. It is recommended that people with diabetes live a general physically active lifestyle, as well as engage in aerobic exercise, strength training, and regular stretching.(2) It should be stated that physical activity is defined as bodily movement produced by the contraction of skeletal muscle that requires energy expenditure in excess of resting energy expenditure. Exercise is defined as a subset of physical activity: planned, structured, and repetitive bodily movement performed to improve or maintain one or more components of physical fitness. The terms "physical activity" and "exercise" are often used interchangeably. Lastly, physical fitness is defined as including cardio-respiratory fitness, muscular fitness, and flexibility.(4)

Approximately 54.8% of adults diagnosed with diabetes are obese.(5) Since many people with type II diabetes are overweight or obese, this type of exercise is beneficial because there is less load on the joints, thereby enabling an enjoyable experience that the person is more likely to stick with. If the person with diabetes experiences lower limb numbness, aquatic exercise may be a better alternative. If the person chooses other forms of exercise, they must be sure to pay special care to the condition of their feet, and any blisters or sores that may form, since a major concern for people with diabetes is poor circulation. In addition, any kind of exercise that raises blood pressure is likely not the best option for someone with type II diabetes. This includes lifting heavy weights or performing static, or isometric, exercises.

After it is determined that the patient is ready to engage in a regular exercise routine, there are several options as to what types, the duration, and the intensity of exercise for that individual.

According to the U.S. Surgeon General’s report, it is prescribed that people with diabetes live an active lifestyle by, for example, using the stairs instead of the elevator, parking their car further from their destination, and minimizing sedentary activities such as watching television. In addition, it is recommended that people with type II diabetes exercise for a minimum of 30 minutes a day, approximately three to five days per week. The effect of increased insulin sensitivity following exercise lasts for approximately 72 hours. Therefore, people with type II diabetes should not allow more than two consecutive days to pass without exercising. There is evidence that resistance training results in an increased period of insulin sensitivity following exercise, possibly due to the increased muscle mass. (4)

In one study, the greatest effect of exercise on HbA_1c was seen with the highest exercise intensity (6). HbA1c is a test performed on people with diabetes in order to determine their blood glucose levels for the previous two to three months. In this study, subjects exercised at 75% of their VO₂ max with some intervals at even higher intensity, for 55 minutes three times a week, including five minutes of warm-up and five minutes of cool down.

There are several types of exercise for people with type II diabetes. When considering aerobic activity, walking, running, bicycling, and swimming are traditional and effective options. Although, if the person is obese, overweight, or experiences peripheral neuropathy, these types of aerobic activity may be limiting. As mentioned earlier, aquatic exercise is an alternative that many find to be advantageous. Water allows the person to feel lighter and more buoyant, and therefore this may make it easier for someone who is obese or overweight to gain similar benefits. The overall goal is to elevate heart rate and recruit large muscle groups.

Strength training may produce faster changes in body composition and functional status due to the gains in muscle mass.(4) This is more rewarding to the client and will improve their motivation, which is a critical factor is determining their adherence to the program. “With increased age, there is a tendency to progressive declines in muscle mass, leading to "sarcopenia," decreased functional capacity, decreased resting metabolic rate, increased adiposity, and increased insulin resistance, and resistance training can have a major positive impact on each of these.”(4)

Stretching has been shown to increase range of motion and reduce the risk of injury, although there is some controversy as to whether it helps with metabolic control.(4)

There are certain situations when exercise should be avoided for a person with diabetes. One example is if hyperglycemia, or high blood glucose, occurs. The American Diabetes Association recommends that exercise be avoided if fasting glucose levels are >250 mg/dl and ketosis is present, and performed with caution if glucose levels are >300 mg/dl even if no ketosis is present.(4) In comparison to hyperglycemia, hypoglycemia, or low blood glucose, should also be considered before exercising. Exercise can cause hypoglycemia due to increased need for fuel, which is more of a concern during prolonged exercise. Medication dose and carbohydrate consumption should be considered, as these levels may need to be modified when an exercise routine is added. In addition, certain medications including diuretics, ß-blockers, ACE inhibitors, aspirin, and lipid-lowering agents are often taken by those with diabetes. These medications may hinder the person’s exercise capacity, so proper attention should be paid to these interactions.

It is now clear that exercise has great benefits for people with type II diabetes. A doctor should always be consulted before beginning any exercise program, as there are certain considerations to take when prescribing the proper exercise routine. Even still, there are multiple types of exercise options for people with diabetes to engage in. The main types of exercise to include in a routine are aerobic, strength, stretching, and an overall active lifestyle.

Reference List:

1. American Diabetes Association. Retrieved March 21, 2009, Web site: http://www.diabetes.org/home.jsp
2. U.S. Department of Health and Human Services, What I need to know about Physical Activity and Diabetes. Retrieved March 22, 2009, from http://diabetes.niddk.nih.gov.lp.hscl.ufl.edu/dm/pubs/physical_ez/physactivity.pdf
3. Tuomilehto, Jaakko (May 3, 2001). Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. The New England Journal of Medicine, 344, Retrieved March 22, 2009, from http://content.nejm.org/cgi/content/full/344/18/1343
4. Sigal, Ronald (2004). Physical activity/exercise and type 2 diabetes. Diabetes Care, 27, Retrieved March 22, 2009, from http://care.diabetesjournals.org/cgi/content/full/27/10/2518#R121
5. (November 19, 2004). Prevalence of overweight and obesity among adults with diagnosed diabetes --- United States, 1988--1994 and 1999--2002. Center for Disease Control, 53, Retrieved March 22, 2009, from http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5345a2.htm
6. Mourier, A (1997). Mobilization of visceral adipose tissue related to the improvement in insulin sensitivity in response to physical training in NIDDM. Effects of branched-chain amino acid supplements.Diabetes Care, 20, Retrieved March 22, 2009, from http://www.ncbi.nlm.nih.gov/pubmed/9051392
   

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