"People with SCI have an increased risk of DM and CVD due primarily to a sedentary lifestyle and a large mass of paralyzed muscle."
Diabetes Mellitus (DM) is a chronic systemic syndrome characterized by high blood glucose. The human pancreas secretes a hormone called insulin, which facilitates the entry of glucose into all tissues of the body (Lewis & Collier, 1992). In a person with DM, the entry of glucose into tissue cells is impaired due to a deficiency of insulin produced or altered tissue cell receptors (American Diabetes Association, 1996). There are two variations of DM: Type I and Type II (Campaigne & Lampman, 1994). In Type I DM, the human pancreas produces very little insulin or none at all. In Type II DM, the human pancreas often makes an excessive amount of insulin, but tissue cells are resistant to insulin and therefore cannot use glucose as energy (Campaigne & Lampman, 1994).
Cardiovascular Disease (CVD) as described by the Heart and Stroke Foundation (1993) is a broad group of conditions, of which the major components are ischemic heart disease and stroke. Other conditions include arrhythmias (disturbance to heart rhythm); hypertension (high blood pressure); valvular heart disease (conditions of heart valves); peripheral vascular disease (that affecting the arteries and veins), and myocardial disease (conditions affecting the heart). It costs the Canadian Health Care System an estimated $17 billion annually to support those who survive and live with CVD (MacLean, 1994).
DM Mellitus in People with Spinal Cord Injury (SCI)
Type II DM is a more serious problem in people with SCI than in people without a disability. Recent research reported that 22% of people with SCI had Type II DM compared to 6% in a non-disabled sample, and that 56% of people with SCI had an abnormal glucose metabolism compared to 20% in a non-disabled sample (Bauman & Spungen, 1994). In fact, people with SCI have approximately four times higher risk of developing DM than the general population. This high incidence of impaired carbohydrate metabolisms is due to physical inactivity (Bauman & Spungen, 1994), a large amount of paralyzed muscle tissue (Burnham et al., 1996; Andersen, Mohr, Biering-Sorensen, Galbo, & Kjar, 1995), and changes in body composition after SCI (Bauman & Spungen, 1994; Bjorntorp, 1990; Despres, Sital, Lupien, Andre, & Claude, 1990). Therefore, it is very important to prevent DM in people with SCI.
Cardiovascular Disease in People with Spinal Cord Injury
Cardiovascular Disease (CVD) is a major cause of death and occurs at a younger age in people with SCI compared to people without a disability (Bauman et al., 1992a, 1992b). Risk factors for CVD are divided into those that are changeable (modifiable) and those that are unchangeable (nonmodifiable). Those that are modifiable are: cigarette smoking; abnormal blood pressure; high blood cholesterol levels; improper diets; reduced high density lipoprotein cholesterol; DM; abdominal obesity and sedentary lifestyle (Consultants Olympic Inc., 1995; Genest & Cohn, 1995; MacLean, 1994; Nair, Nargundkar, Johnasen, & Strachan, 1990). Those that are nonmodifiable are age, gender, and hereditary factors (Genest & Cohn., 1995). Research has demonstrated that reduced high density lipoprotein levels particularly raise the risk of CVD in people with SCI (Bauman et al., 1992b; Ragnarsson, Pollaack, & Twist, 1991). These reduced high density lipoprotein levels are attributed to physical inactivity (Ragnarsson et al., 1991).
Nutritional Intervention of DM and CVD
The ultimate goals of nutritional management of DM and CVD are to normalize blood glucose and achieve desirable blood lipid levels. Nutrients of most concern in these diseases are carbohydrates, protein, and fat.
Carbohydrates are found in starchy foods such as potatoes, rice, pasta, breads, and cereals. There are three types of carbohydrates: complex carbohydrates, simple carbohydrates, and dietary fibre (Williams, 1988). Simple sugars such as sucrose and glucose increase blood glucose faster and to a higher level. Therefore, ingestion of complex carbohydrates is recommended (45 to 60% of total energy). In the digestive process, complex carbohydrates are broken down into simple sugars, like glucose, and are absorbed into the blood. Once in the blood, glucose stimulates the pancreas to secrete insulin into the blood. Insulin is a hormone which facilitates uptake and utilization of glucose by various tissues in the body, notably muscles and adipose tissue (Williams, 1988).
Fibre has recently emerged as an important dietary component, a therapeutic agent, and preventer of DM and CVD. Fibre is found in foods like fruits and vegetables, beans, and whole grain products. Vegetables particularly high in fibre are broccoli, cauliflower, and brussels sprouts (Williams, 1988). A high fibre diet slows nutrient digestion and absorption, thereby allowing blood glucose levels to increase more slowly while reducing insuling requirements. A high fibre diet has also been shown to decrease cholesterol levels and blood fat such as triglycerides, which increase the risk of CVD.
Ten of 20% of total calories should come from protein. Proteins are found in both vegetable and animal sources. Vegetable proteins come from such foods as beans, peas, and nuts. Animal proteins come from foods like eggs, meat, milk, and poultry.
Less than 30% of total calories should come from fat. Diets that include large quantities of dietary fat increase the risk for DM and CVD. There are several types of dietary fat: saturated, monounsaturated and polyunsaturated. Saturated fat is found in animal products such as butter, shortening, lard, coconut oil, and palm oil. It has been shown to increase blood cholesterol and fat, both of which are highly correlated with CVD (Williams, 1988). Due to the detrimental effects of saturated fat, consuming monounsaturated and polyunsaturated fat is encouraged. Monounsaturated fat is commonly found in olive, canola, and peanut oil, and is known to decrease cholesterol. Polyunsaturated fat contains omega-6 fat, derived from vegetable oils (safflower, sunflower, corn, and soybean), and omega-3 fat, which comes from fish and marine mammals. Both omega-6 and omega-3 fats decrease cholesterol, and omega-3 fat can notably lower the risk of CVD by reducing serum cholesterol levels (Williams, 1988).
In summary, dietary intervention plays an important role in the prevention of DM and CVD. A few recommendations to keep in mind for better health and increased prevention of CVD.
* Eat a wide variety of fruits and vegetables.
* Maintain a normal body weight. Excessive body weight may contribute to the development of disease.
* Decrease your consumption of foods that are high in total fat, saturated fat, and cholesterol. Do this by eating low fat meats and butter; fish; fewer eggs, and fewer dairy products high in fat.
* Eat more foods with adequate starch and fibre.
* Reduce your consumption of refined sugar by checking food labels for corn syrup, dextrose, fructose, malt sugar, and corn sweeteners.
* Reduce candies and desserts.
* Use less salt. Drink alcohol in moderation Williams, 1988, 288-291
Aerobic Exercise as Prevention Against DM and CVD
Physical activity has been shown to decrease the risk of developing CVD (Brenes, Dearwater, Shapera, LaPorte, & Collins, 1986) and DM. However, activities of daily living in people with SCI are not sufficient to maintain muscular and cardiopulmonary systems (Janssen, Van Oers, Van Der Woude, & Hollander, 1994). Therefore, supplemental exercise training is desirable for people with SCI in order to develop and maintain fitness to subsequently decrease the risk of developing DM and CVD. In one study, eight people exercised for one hour daily, stair climbing, over a period of six weeks. It was found that physical exercise decreased the risk factors for DM considerably (43%), more than that which had been reported with the drugs metformin (16-25%) or troglitazone (about 20%) (Perseghin et al., 1996). Another study demonstrated that men with SCI following eight weeks of moderate intensity wheelchair exercise decreased their total cholesterol (-8%), increased their high density lipoprotein levels (20%), and decreased their low-density lipoprotein-cholesterol levels (15%) (Hooker & Wells, 1989). These beneficial alterations in the blood lipid and lipoprotein profiles translate into a 20% reduction in risk of CVD (Hooker & Wells, 1989). Therefore, it is important for people with SCI to engage in regular physical activity so that DM and CVD can be prevented.
Aerobic training for people with SCI has been limited to upper body exercise, yet there are still many other unexplored opportunities for people with SCI to be physically active. For example, arm crank exercise, wheeling exercise, wheelchair basketball, and wheelchair tennis all provide great fitness benefits (Janssen et al., 1994). Although upper body exercise is beneficial, the relatively small mass of upper body musculature available for exercise (in people with SCI) does not elicit a sufficient magnitude of cardiopulmonary and cardiovascular responses during exercise (Astrand & Rodahl, 1977; Vokac, Bell, Bautz-Holter, & Rodahl, 1975). Prolonged excessive upper body endurance exercise for individuals with SCI can be stressful on upper body joints and muscles, particularly on shoulders and wrists which are required for self-care and wheelchair mobility (Ragnarrson et al., 1991). Overuse injuries to the upper body are commonly seen in people who have lived many years with a SCI and may negatively affect a person's well being and quality of life (Ragnarsson et al., 1991). Therefore, functional electrical stimulation, FES-assisted exercise, another mode of aerobic exercise has been introduced to people with SCI.
FES-Assisted Lower Body Exercise
Advanced computer technology has made it possible to stimulate multiple paralyzed muscle groups sequentially for long periods of time in order to produce relatively complex motor activities such as pedaling a cycle ergometer (Hooker, Scremin, Mutton, Kunkel, Cagle, 1995; Figoni, et al., 1988; Ragnarsson, 1988). The ERGYS system is a computer-controlled bicycle which applies electrical stimulation through surface electrodes to the buttocks, front and back of the thigh in a sequence to allow pedaling at 50 rpm for up to 30 minutes (Glaser, 1994). ERGYS can be used alone or in combination with arm exercise to improve musculoskeletal, peripheral, and cardiovascular fitness for people with SCI (Glaser, 1994; Krauss et al., 1993). It also results in improved circulation of the lower limbs, improved cardiovascular fitness (Andrews & Wheeler, 1995; Glaser, 1994), and decreased incidences of pressure sores and blood clots (Petrofsky & Stacy, 1992). Also, ERGYS exercise has the potential to decrease risk factors associated with DM and CVD in people with SCI. ERGYS exercise increases physical activity and stimulates the large paralyzed mass of denervated leg and gluteal muscles which results in body composition changes (Burnham et al., 1996) that may consequently decrease cholesterol levels in blood and improve glucose metabolisms (Brenes et al., 1986).
Summary and Recommendations
People with SCI have an increased risk of DM and CVD due primarily to a sedentary lifestyle and a large mass of paralyzed muscle. Exercise and diet have proven to be the best ways to prevent and treat both DM and CVD. Physical activity combined with diet in persons with SCI is therefore desirable to help prevent secondary complications and improve quality of life. Upper body exercise alone may increase physical activity level but does not stimulate the large mass of paralyzed muscles which is the main reason for the increased incidence of DM and CVD. FES-assisted exercise improves circulation of the lower limbs, cardiovascular fitness, and decreases the incidence of pressure sores and blood clots. In summary, exercise, notably upper body exercise and FES-assisted exercise, is recommended as a means of increasing physical activity and developing cardiopulmonary fitness to decrease the risk of developing DM and CVD.
The information in this article was presented to people in the Edmonton community in order to educate and raise awareness on ways to prevent diabetes and cardiovascular disease. From this seminar, we hoped to recruit participants for post graduate work. The seminar was supported by the Spinal Cord Injury Treatment Centre Society (SCITCS), The Great Canadian Bagel, and Blimpies. We would like to thank Louise Miller, Robert Burnham, Garry Wheeler, Rick Gingras and Neil Pierce and Larry Pempleit from the Alberta Paraplegic Association for their contributions to the seminar. We would also like to thank the many volunteers who helped us conduct the seminar. Michael Penkman, Tony Webster, Birgit Siefort, and Mandy Korthe. Many thanks to the Therapeutic Alliance and the Alberta Paraplegic Foundation for their financial contributions to the resulting research.
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Christine B. Weiss is a Master's student in Adapted Physical Activity in the Department of Physical Education and Recreation at the University of Alberta. Her research is investigating the effects of exercise on lipid levels in people with spinal cord injury.
Justin Y. Jeon is a Master's student in Adapted Physical Activity in the Department of Physical Education and Recreation at the University of Alberta. His research is examining the effects of exercise on glucoregulation, insulin sensitivity, and diabetes mellitus in people with spinal cord injury.
Miyoung Suh is a doctoral student in the faculty of Agricultural, Food, and Nutritional Science. Her research is investigating the effects of fatty acid metabolism on the retina of the eye.
Robert D. Steadward is a professor in the University of Alberta's Faculty of Physical Education & Recreation. He is Founding Director of the Rick Hansen Centre, a fitness, health, lifestyle, and research facility for people with disabilities, and is President of the International Paralympic Committee, world-governing body for athletes with disabilities.…