The application of walking exercise to special populations may serve as one of the best reasons yet to start on a walking program for improved health. This article will concentrate on one area that walking may have a profound impact on – that of Gestational Diabetes Mellitus during pregnancy. Regular exercise has effects in diabetes in general, and the focus here is its relevance with women who have two concerns – exercise during pregnancy, and dealing with the effects of diabetes during their gestation.
Diabetes in Pregnancy
Gestational diabetes is a disorder that affects a small but significant percentage of women during their pregnancies. It is defined as abnormally high blood sugar levels after a meal, and is associated with changes in hormonal levels during the second trimester on of pregnancy. These physical changes, as well as a family history, body weight above 115 % of ideal, and poor dietary patterns may predispose women to GDM.
Approximately 3-5% of women will encounter GDM during their pregnancy. It rate is higher in low socioeconomic status women, and in Hispanics. The results of uncontrolled GDM throughout pregnancy may result in fetal macrosomia (baby birth weight above nine pounds), and increases the risk for neonatal morbidity, compensatory low blood sugar reactions in the neo-nate, and cesarean section. It is the major cause of still births in the United States.
GDM is associated with fetal macrosomia because of high levels of insulin secretion by the fetus in response to high levels of maternal sugar that cross the placenta. The mother’s own insulin is too large of a molecule to pass through the membrane, so the fetus must “overproduce” its own to compensate for the flood of sugar. Insulin is a growth hormone, and this is the cause of fetal macrosomia.
Screening for GDM
The usual diagnosis of GDM is by a 3 hour glucose tolerance test, whereby the mother drinks a 100 gram sugar solution, hoping to keep glucose levels from elevating too high over this time. The standard criteria is: Fasting levels < 105 mg/dl, 1 hour > 190, 2 hours > 165, 3 hours > 145 mg/dl. If a women is higher at any two time points, she is diagnosed with GDM.
Standard treatment of GDM is usually diet modification, staying with a meal plan higher in protein and fat to blunt the post-prandial (after meal) response. Women are encouraged to measure their own blood sugar levels at various times during the day with a home glucose monitor, which will record the results of a small drop of blood on a reflectance strip, and gives blood sugar results in a short time period.
If a standard diet is not successful in keeping blood sugar levels under control after meals, or during the fasting state, then insulin therapy is usually ordered by the doctor. It is done so because oral agents (used with many older adults with diabetes), is contraindicated in gestational diabetes, because of suspected risks to the fetus.
Insulin is administered around meal time on what is known as a “split routine”; or trying to match insulin amounts to types and amounts of foods eaten. If it is successful, then blood sugar levels will be in good control most of the time. Many women are not happy with the idea of taking insulin injections over the last two months of their pregnancy, and many are looking for other alternatives to this type of medical treatment.
Exercise and Diabetes
Exercise is one of the cornerstones of diabetic treatment. It has been used in type I (insulin-dependent), and type II (non insulin-dependent) diabetes for years. Exercise has an “insulin-like effect” on the muscle, causing blood sugar levels to drop, independently of insulin in most cases. It has been studied in many adults with diabetes, but until recently, not much in pregnant women.
The reason there was little research performed in GDM is that many physicians were not sure of the benefits of exercise in a normal pregnancy, let alone a high risk pregnancy such as a diabetic woman. After about 15 years of experiments, from the late 1970’s until the early 1990’s, the amount of scientific research in the area was increased, and the latest word in sports medicine is that many women are better off performing regular exercise as part of their pregnant routine, than being sedentary over their gestation. It mimics the evidence for people in general, in terms of basic health maintenance.
Exercise in GDM
One of the first studies performed in GDM used bicycles to look at blood sugar response to a controlled exercise situation. Results showed that indeed, these levels did lower in response to exercise. Other studies looked at diet and diet along with exercise and its effects on both short term, and long term blood sugar control. Again, those women who performed regular exercise showed improvement in their blood sugar control, even above that of diet alone. In fact, those exercisers used conditioning regimens in leu of insulin to keep themselves in control during the last half of their pregnancy.
The women in most research studies exercised on aerobic machines, keeping track of work load, and other criteria, such as fetal response to exercise (via heart rate monitoring), maternal heart rate and blood pressure, and of course, blood sugar response. The emphasis of the research also showed that some types of exercise machines, such as the upper body arm crank, and recumbent bike were better tolerated by exercising women, as they did not have any uterine contractions during exercise, compared with other forms of exercise which had a few contraction episodes, prompting an early ceasing of exercise (to be on the safe side).
The Benefits of Walking
Walking is coming into its own as a major health enhancement tool. One of the big questions as to the beneficial aspects of exercise in general is not so much if it is good for healthy people (does exercise make you healthier, or do healthy people naturally gravitate to exercise?), but what are its effects on those with disease.
Walking has been shown to reduce cholesterol levels, have a protective effect from coronary heart disease, reduce body weight, reduce blood pressure, and improve circulation in medical patients. The question to be asked is – what type of effect would it have in diabetes?
Many clinical exercise physiologists report that one of the only types of exercises that they can prescribe to their adult onset diabetic patients is daily walking – since many do not have exercise machines, or belong to a health club. They must therefore be creative in working with “home-based” exercise programs that their patients will adhere to, and benefit their diabetes control.
Walking about 30 minutes after eating has been beneficial in keeping post prandial blood sugars in control for many patients. They feel that they can accomplish a 20 to 30 minute walk 2 or 3 times per day, and over a couple of months, they feel better. Many have reduced their medication levels during their tenure in their walking program.
An application to GDM
How can the pregnant diabetic women accrue the benefits of exercise without an added financial expense, or jeopardizing her or her babies health? Barring any orthopedic limitations, walking 2 or 3 times a day may just be the ticket to enhancing her health, and keeping her blood sugars in check over the last half of her pregnancy. Many women feel that exercise programs become more fatiguing as the third trimester approaches, so even getting out for a walk and increasing circulation is a big help in keeping them feeling good.
A sample program would include a mid morning walk of 1 to 1.5 miles with a couple “up hill” challenges. An afternoon walk would include a pre-planned route that also included some small hills, but that is not too congested with traffic.
Walking at the local track will offer women a planned distance, as all tracks are a quarter mile in length. They also have soft surfaces for shock absorption, and usually are not crowded until track practice at 3-4 p.m.
Walking with a partner (perhaps one who is also pregnant) may help in keeping motivation levels high during pregnancy. With a diagnosis of GDM, and a growing belly, many women feel that they are to big to begin with, let alone trying to keep up with those who may not wish to keep their pace.
Good walking shoes are a must. Many women gain enough weight in the second trimester to warrant purchase of a new pair. This may help in case there are any minor swelling problems in the feet, and newer shoes are more stable. To date, there is not specific shoe for pregnancy, but there may be a market for them, with the advent of the new “baby boom”.
One aspect of good diabetes control is that of self-blood sugar monitoring, as highlighted above. Self monitoring lets any diabetic person know where their sugar levels are at any time of the day. In exercise, it sets the limits of conditioning, as higher levels may dictate more prolonged exercise programs to “burn off” more sugar, and lower levels may dictate the ingestion of a carbohydrate to prevent hypoglycemia (low blood sugar) reactions after exercise has finished. None the less, having a home monitor (usually reimbursed by insurance upon physician prescription) plays an important part of the diabetic exercise regimen, and should be used by any GDM women who wishes to perform walking programs (or any exercise) to keep in good metabolic control during her pregnancy.
It should always be remembered that any exercise program should be built up in terms of intensity and duration, including walking. There are many women who would not think of walking for 30 minutes two or three times a day, because of swelling, morning sickness, backache, or headaches. Consultation with your obstetrician should provide proper guidelines for any medical considerations needed to perform exercise safely, and within individual limits.
Then, working with an instructor, or on your own, exercise up to your perceived limits, and stay in those limits as you build endurance over a couple of weeks. It is possible to increase fitness levels during pregnancy, if they are done systematically. Walk for 5 minutes as a brisk pace, and gradually increase. If the goal is blood sugar control, compare walking times with post walking sugar checks. Over time there should be a consistent pattern.
Exercise not only has been touted as a good therapeutic treatment for diabetes, but recent epidemiology studies also shows a strong association between exercises levels, and the reduction of diabetes in general. This is known as primary prevention. Those persons who exercised the most had the least occurrence of the disease. This types of studies have given tremendous support to the advent of exercise in the diabetic population.
One case report highlighted a previously diagnosed GDM women in her first pregnancy who exercised throughout her second. The glucose tolerance test was normal – essentially preventing the occurrence of the disease in the second pregnancy. These are powerful reasons for pregnant women to inquire about exercise, and for doctors to prescribe it more often.
As more people in this country switch from heavy exercise routines, to health promoting activity programs, walking is emerging as a viable daily endeavor. Pregnant women who have been diagnosed with GDM may find that a simple walking program can keep their blood sugar levels under control, keep their body fat levels from increasing dramatically, and enhance their overall health. It all starts with the first step.