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THE CONVERGENCE OF EXERCISE, DIABETES AND HEART RATE MONITORS

Authors: Cathy Mullooly, M.S.. C.D.E., Director Exercise Physiology Joslin Clinic Pam Fernandas, Elite athlete.

The Benefits of Physical Activity

The American public is flooded with information on how physical activity impacts health and wellness. Scientific studies show that dozens of medical conditions are substantially improved and in some cases prevented by participation in a fitness program.1 Medical as well as health and fitness professionals are actively promoting physical activity as a means to reduce the risk of developing chronic or debilitating diseases and maintaining health. Even with this wealth of information, more than 60 percent of adults do not participate in regular physical activity. Twenty-five percent of all adults admit that they are not active at all. These American’s are more likely to be older in age, female, less educated and make a lower income.

People with disabilities are also less likely to engage in regular moderate physical activity than people without disabilities. Yet, the argument can be made that they have even more to gain from participating in some form of physical activity. Participation in physical activity can promote health and help prevent the progression of many conditions. Exercise can improve stamina, increase muscle strength, bone density, and reduce the symptoms of anxiety and depression that are often present with chronic diseases and disabilities. Overall, physical activity can help to improve mood and promotes feelings of general well being while living with a disability. A disability should not be an excuse to be sedentary. In fact, the lack of physical activity may shorten a life.

Improving A Chronic Disease Through Exercise: Diabetes

While there are many chronic diseases and disabilities that inhibit participation in physical activity, the content of this paper will focus on those associated with Diabetes Mellitus. Diabetes devastating effects have long been recognized and are well-documented 3,4. In 1996, 16 million Americans were estimated to have diabetes. This number is expected to increase in the next century. Diabetes is currently listed as the sixth leading cause of death by disease in the United States. The true devastation of the disease comes in its many complications. Cardiovascular disease (CD) has the largest impact on the morbidity and mortality of individuals suffering from diabetes. CD is 2 to 4 times more common in people with diabetes. It is present in 55 - 75% of diabetes related deaths. Other cardiac risk factors such as hypertension (present in 60 - 65%) and lipid abnormalities (present in up to 44%) are also common. Diabetes is also the leading cause of blindness, cataracts, end-stage renal disease and lower extremity amputations. Diabetes care in the USA alone is estimated at $92 billion annually.

While these figures are discouraging, many of these complications are known to be associated with long-standing hyperglycemia. A number of recognized studies have shown that any improvement in diabetes control (changes in the glycohemoglobin A1c) dramatically reduces diabetes complications. 5,6,7 Also, many people with diabetes are living active lives without any restrictions due to the disease. This is the direct result of regular exercise. In fact, a respectable number of diabetic patients are elite professional athletes. The exact role that exercise plays in preventing long-term complications has been difficult to research. However, there are a significant number of patients who lead a very active life reducing the severity and eliminating the complications commonly associated with diabetes.

The therapeutic use of exercise to control diabetes is not new. It was prescribed as early as 600 BC by the Indian physician, Sushruta, and was widely recommended by physicians of the 18th century. In the early 1900’s, the impact that a single exercise session has on blood glucose levels was first measured. 8,9 Since then, the long-term impact of exercise has also been investigated. Studies have proven that HbA1C levels improve when regular exercise is performed 10,11,12 and that some factors involved in diabetic complications can be positively impacted.13 Monitoring the Intensity Level of an Exercise Prescription

Many professional organizations (i.e., American College of Sports Medicine, American Heart Association, American Diabetes Association, American Association of Cardiovascular and Pulmonary Rehabilitation) have published clinical guidelines using heart rate for prescribing a safe and appropriate exercise program. Athletes regularly monitor heart rate to achieve maximum training effectiveness, avoid injury, and ultimately improve performance. Heart rate provides an indirect measurement of how much oxygen the body is consuming for the production of energy, known as oxygen uptake or VO2. Heart rate ranges are usually calculated from a measured or estimated VO2MAX (maximal oxygen uptake). Exercising within a certain heart rate range provides the most beneficial effects. Ranges vary depending on an individuals goals and limitations. By setting ranges appropriately, weight loss, increased cardiovascular fitness, combating depression, improved insulin resistance (possibly preventing diabetes), improved athletic performance and lipid levels, and hypertension, all can be positively effected.

Diabetes Complications and Exercise for Diabetes Control

While exercise is accepted as an important component in diabetes control, the presence of diabetes complications requires certain precautions. Because of the prevalence of cardiac disease in the diabetic population, heart rate should be closely monitored. In a supervised session, trained clinical exercise physiologists can measure the heart rate by a variety of means and then set the exercise workload accordingly. Patients exercising on their own may not be able to do so. For example, the presence of diabetic neuropathy inhibits pulse taking because of the loss of the feeling at the fingertips. In these situations an important tool is a heart rate monitor. One such device we have found particularly useful is the HEARTalker™ heart rate monitor because of its easy to understand verbal feedback.

The heart rate also becomes an important measure in the presence of retinopathy (eye disease) and nephropathy (kidney disease). At certain stages in both of these disease processes, blood pressure changes need to be closely guarded. Any sudden or extreme changes in this biological parameter is thought to exacerbate these conditions which may then lead to vision loss or kidney damage. By measuring the linear response of heart rate to blood pressure changes during exercise, a maximum heart rate level during exercise can be prescribed where the blood pressure response is acceptable. Constant feedback is necessary throughout each workout to insure these parameters are not exceeded.

Diabetic with vision loss would also find it impossible to palpitate for a pulse because of the need to use a timepiece to count seconds. In these instance, a HEARTalker talking heart rate monitor provides the heart rate feedback required.

Athletes at all levels of experience acknowledge that monitoring heart rate is a help in optimizing athletic performance. Those athletes hindered by a disease such as diabetes should not be prevented from reaching their peak performance because modern technology is unavailable to them. Again, the HEARTalker monitors fill this void very well so even those suffering from severe complications of diabetes can receive the benefits of heart rate training.

Real Life Experiences of an Elite Athlete

One such athlete is Pam Fernandes. Pam is blind, she also happens to be an elite athlete, and a five-time National Champion for the United States Association of Blind Athletes (USABA) cycling team. Pam earned the first USABA International medal in cycling by capturing the silver at the World Championships in Belgium. At the Atlanta Paralympic Games Pam won a bronze in the one Kilometer Time Trial. Pam lost her sight 17 years ago as a result of complication from type I diabetes. She is also a kidney transplant recipient. For the past 17 years Pam has dedicated herself to maintaining an active life style, remaining independent, staying fit, and competing as a world class athlete. Pam has not allowed blindness to stop her. She constantly looks for ways to help her achieve her goals in life.

Health and fitness have always been important to her. As a sighted youngster she was involved in many team sports, but with the onset of her blindness and subsequent kidney failure at the age of 21 she could no longer exercise in the same manner as before. After the kidney transplant in 1987 she yearned to become physically active again, both for health reasons and to lose weight gained while recuperating and from the anti-rejection medication. Joining a local gym and enthusiastically throwing herself into aerobic exercise and weight training, Pam gained strength, lost weight and increased her cardiovascular fitness. The positive effects exercise had on her physically and mentally, challenged her to set goals and strive to work harder to meet them.

In 1993 Pam discovered tandem cycling when attending a racing camp held at the U.S Olympic Training Center in Colorado Springs. The camp accelerated her learning curve for cycling and ignited a passion for the sport. She learned new training methods and about the body’s physiology, diet, and competitive racing. She was also exposed to heart rate monitoring for the first time.

Unfortunately, existing heart rate monitors were not very friendly to someone who is blind. The available wireless monitors used a digital watch to provide heart rate feedback. A beeping sound alerted the user when exercising out of the prescribed target heart rate zone. This was difficult for Pam to use, and required that she depend on others to set target zones than help her interpret the monitor’s feedback. She was determined to find a way to get the information she needed in order to train like every other elite athlete.

Old Problem Solved by New Technology In 1998 Pam found the solution to her heart rate training dilemma. A friend suggested she try a new heart rate monitor, the HEARTalker Personal Trainer. With all the heart rate feedback delivered verbally, the HEARTalker was just the tool Pam had been seeking to help her train independently. The HEARTalker monitor performed well for her and it was not expensive. Many products produced just for the disabled cost too much to be widely used. Like any piece of new equipment Pam experimented with it, walking around the house wearing it to get a feel for how it worked. To quote Pam, "the monitor is so easy to use even a blind person can use it". Training became more enjoyable because the feedback she was getting helped her trainer more effectively and she again found herself to be more self dependent in her workout activities.

How Heart Rate Training Works The competitive athlete who uses a heart rate monitor first must determine their maximum heart rate (MHR). This value can be determined by a number of ways. The most popular estimated method is to use the value 220 minus the person’s age. This method is appropriate average individuals but is inadequate for the competitive athlete because of their conditioning. For competitive athletes the VO2MAX (maximal oxygen uptake) test is often used to determine MHR. Other test methods are also available. Once the MHR value is determined, an effective training program can be established.

Pam’s training included workouts at heart rates of 70%, 80% and 90% of her MHR, so heart rate monitoring has to be accurate and reliable. On easy workout days her heart rate was kept below 70% MHR. Certain workouts require Pam to keep her heart rate at 140 BPM for one hour. Before HEARTalker this would have been impossible to monitor. Needless to say, her coach is excited about this new piece of training equipment.

For competitive athletes one of the biggest problems is over training. Too frequently the athlete succumbs to the seduction that "more is better". Combine this with a "type A" personality and you have a recipe for disaster, put another way, the road to certain injury. If the athlete is knowledgeable about how the heart responds to training the intensity can be adjusted appropriately. Heart rate trained athletes know that if the resting heart rate is elevated something is wrong. Additional warning signals include rapid increases in heart rate and slower recovery to normal levels. These may be signals that the body has not recovered from a previous workout, or an indication of other more serious problems. Heart rate can be a reliable indicator as to the overall health and fitness of the body. Regular use of a heart rate monitor makes it possible for anyone to better understand their body in order to pace themselves for a safer more effective exercise program.

Heart Rate Monitoring for the Average Diabetes Patient

The HEARTalkerÔ Personal Trainer heart rate monitor is not just for the competitive athlete. The heart is the most important muscle in every body, not just the body of athletes. When the heart becomes more physically fit endurance is improved. Exercising with a heart rate monitor helps anyone exercise at the safest and most beneficial level based on age and fitness level.

Exercise benefits previously mentioned such as weight loss, lower blood pressure, reduction of stress and depression can all be realized sooner and with less strain when a heart rate monitor helps manage the intensity of the exercise. Cardiovascular benefits can help improve the quality of life many patients. Perhaps the biggest benefit to diabetics is the positive effect exercise has on lowering blood sugar which results in the need for less insulin. Exercise as simple as a brisk walk for 30 minutes at 70% MHR can have a significant effect on blood sugar. Careful monitoring of blood sugars is required to achieve best results. Make exercise a daily part of life. REFERENCES

  1. Designed for Action. ACSM’s Health & Fitness Journal, May/June 1999, Vo1 2, No. 3, 30-37.
  2. U.S. Department of Health and Human Services: Physical Activity and Health: "A Report of the Surgeon General." Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Washington, DC, U.S. Govt. Printing Office, 1996.
  3. National Diabetes Information Clearinghouse. Diabetes Statistics. NIH Publication No. 96-3926. October, 1995.
  4. American Diabetes Association. Diabetes 1996:Vital Statistics,1996.
  5. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N. Engl. J. Med. 329:977-986, 1993.
  6. Ohkubo Y., H. Kishikawa, E. Araki, et al. Intensive insulin therapy prevents the progression of diabetic micro-vascular complications in Japanese patients with non-insulin-dependent diabetes mellitus: a randomized prospective 6-year study. Diabetes Res. Clin. Pract. 28:103-117, 1995.
  7. UK Prospective Diabetes Study Group. Intensive blood glucose control with sulfonylureas or insulin compared with conventional treatment and risks of complications in patients with type 2 diabetes (UKPDS 33)Lancet 352:837-853, 1998.
  8. Lawrence R. D. The effect of exercise on insulin action in diabetes. Brit. Med. J. 1:648-652, 1926.
  9. Marble A. and R. M. Smith. Exercise in diabetes mellitus. Arch. Intern. Med. 58:577-588, 1936.
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  11. Scheider S. H., A. K. Khachadurian, L. F. Amorosa, L. Clemow and N. B. Ruderman. Ten-year experience with an exercise-based outpatient lifestyle modification program in the treatment of diabetes mellitus. Diabetes Care 15(Suppl. 4):1800-10, 1992.
  12. Stratton R., D. Wilson, R. K. Endres, and D. E. Goldstein. Improved glycemic control after supervised 8-wk exercise program in insulin-dependent diabetic adolescents. Diabetes Care 10:589-93, 1987.
  13. Veves A, Saouaf R, Donaghue VM, Mullooly CA, Kistler JA, Giurini JM, Horton ES, Fielding RA. Aerobic exercise capacity remains normal despite impaired endothelial function in the micro- and macrocirculation of physically active IDDM patients. Diabetes 46: 1846-1852, 1997.

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