Physical and Glycemic Responses of Women With Gestational Diabetes to a Moderately Intense Exercise Program ERICP. D URAK, MSc, CSCS Sports Training Institute, New York and Sansum Medical Research Foundation Santa Barbara, California

LOIS JOVANOVIC-PETERSON, MD CHARLES M. PETERSON, MD Sansum Medical Research Foundation Santa Barbara, California

Aerobic exercise machines are becoming more popular. Their use by women with gestational diabetes is reported, and their benefits in improving blood glucose management and in

increasing maternal fitness without undue stress to the fetus are substantiated. Of equal benefit is the use of an exercise

specialist to prescribe an individual exercise program, to increase the safety and effectiveness of the workout, to monitor maternal and fetal wellbeing, to record relevant data, and to provide feedback and information to the patient about the exercise session. The use of exercise specialists in the clinical

setting should prove a useful adjunct to medical and dietary regimens for the woman with gestational diabetes.

The issue of exercise and pregnancy has gained attention in the past few years both in the medical and sport science literature,1.2 and in current health and fitness magazines. Most of the literature generated about exercise deals with both maternal and fetal responses to conditioning programs3 and the proper exercise prescription necessary to enhance fitness without causing distress to the mother or the fetus. The normal pregnant woman undergoes many physiological changes during her pregnancy (Table 1). These changes make it difficult to prescribe exercise programs because of a lack of knowledge about the outcome of the exercise itself: Is it too difficult for the woman to accomplish’? Is it challenging enough to create an exercise stimulus? Will it cause a problem with the fetus during or after the exercise session (such as bradycardia, tachycardia, uterine contractions, etc)1?4.5 From the standpoint of exercise and diabetes management, the most important issues are blood glucose monitoring and safety of the exercise program being prescribed.33 The purpose of this paper is to evaluate current aspects of physical training in gestational diabetes mellitus (GDM) and their impact on parameters of diabetes management. The role of the exercise specialist in prescribing individual exercise will also be discussed.

Reviews of Exercise in

Pregnancy and GELB1

by Wolfe and colleagues6 points out the many respiratory changes that occur during the course of pregnancy. Although most parameters change disproportionately during the three trimesters, there is a general decrease in the Vo, and a general increase in heart rate and cardiac output. Metabolic equivalent (MET) levels have been studied in both diabetic and nondiabetic women during light exercise.~ Results indicate that exercise at low to moderate intensity poses little or no danger to the fetus during the exercise program performed. A current review

This study was supported m part by grants from Cybex, Inc., Ronkonkoma. New Yor4,, and Pro Tec Sports. Huntington Beach. Califurnia Reprint requests to Enr P Durak. MSc, S;~n,um Medical Research Foundauon, 2219 Bath Street, Santa Barbara, CA 931U5.

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Table 1.

Maternal Physiological

Changes During Pregnancy

prefer to engage in personal activities such as swimming, outdoor biking, or jogging. Some fitness enthusiasts choose to exercise on aerobic machines. Performing aerobic exercise indoors requires the use of an ergometer (bicycle, arm, rowing, etc). Ergometers are also widely used in fitness clubs because of space limitations. These machines are helpful in conditioning because work loads can be quantitated and recorded, and improvements in fitness can be established over time.

Physical Conditioning Modalities

These reports all look into the parameters of the physiological responses to exercise and pregnancy, and have helped define limits of exercise thresholds for general exercise prescription. In GDM, glycemic control is perhaps the most critical factor of manipulation in relation to other physiological responses mentioned. Since most GDM patients are diagnosed at approximately 28 weeks, they probably have not undergone any supervised training program, so any effects of training or changes that may have occurred as a result of conditioning programs have not been ascertained. Although exercise should not be too vigorous to cause maternal or fetal complications (such as increased core temperature, excessive fatigue, fetal heart rate arrhythmias, etc), it should be of adequate intensity to elicit some change in blood glucose levels independent of other metabolic factors, such as kilocalorie intake and time of day of exercise.6 Heart rate response and patient rating of perceived exertion (RPE) become important factors in proper dose/response to exercise. RPE has been recommended as a method for monitoring and prescribing exercise intensity during pregnancy8 and, along with monitoring of target heart rate, provides a suitable criteria for which fitness specialists may set up conditioning programs for pregnant women. Blood glucose responses are dependent on food/ percentage of carbohydrate intake and, of course, insulin intake. The goal of exercise therapy in GDM is to obviate the need for exogenous insulin injections in newly diagnosed women and to reduce, if not eliminate, injections in patients who are already using insulin as their sole mode of treatment for their disease. It is very hard to test the effect of exercise when insulin is being used. Each element acts as a mask to the other. Therefore, if exercise is to be used as a treatment modality, it must keep the patient’s blood glucose levels in as good control as if the patient were taking insulin injections

daily. Exercise Trends

Many women who engage in exercise during pregnancy are enrolled in an aerobic class of some type. These courses entail approximately 20 to 30 minutes of moderate, lowimpact aerobic exercise, along with flexibility routines, relaxation techniques, abdominal breathing, and Kegel’s exercises.9 Outside of the classroom situation, some women

Prior to beginning an exercise program, submaximal testing should be done to determine the woman’s initial fitness level so that exercise prescriptions can be individualized. Such testing will also provide insight into heart rate and blood pressure responses prior to exercise. Whatever conditioning mode is chosen, the GDM woman should begin each training session with a blood glucose monitor check, and the initial level should be recorded. The beginning exercise sessions start with women working out moderately on exercise machines based on their initial fitness level, estimation of perceived exertion, and functional work capacity. These aerobic machines train the body in an overall aerobic effect and are used to condition specific muscle groups in a progressive resistance fashion. The Upper Body Ergometer (UBE) (Cybex Fitness, Ronkonkoma, NY) provides resistance for the arms, shoulders, and upper back, which are often very weak in some women. The UBE contains four different revolution settings, and an open-faced dial measuring resistance in kilogrammeters. The trainee sits in a comfortable seat on the machine and is instructed to pedal with her arms to the specific kilogram-meter setting for a specific period of time. If she cannot perform the given work load, the setting is adjusted to her work capability based on her RPE and target heart rate. ~°~~ ~i

The Concept II Rower (Concept II, Morrisville, Vt) exercises buttock, back, shoulder, brachial, and forearm muscles. The rower sits on a padded seat that slides on a track, and pulls on handgrips to turn a flywheel at a given tension. The resistance of the flywheel can be modified by changing the chain on the gear settings. The resistance is measured in watts; other information, such as total distance and caloric expenditure, can also be recorded. The amount of resistance per unit of time is up to the individual, who determines how hard a given force is exerted against the machine. For a pregnant woman, the sliding action is limited by a 24-inch wood beam secured to the track so that her hip and knee joints will not be forced into a full range of motion during exercise. This also allows more effort to be exerted by the upper body. Here the patient is instructed to perform the exercise with a straight posture while pulling against the flywheel. The machine registers the effort of the pulling action in watts, with a mean output represented on the screen. The mean output is recorded during exercise. The PTS Turbo 1000 Recumbent Bike (Pro Tec Sports, Huntington Beach, Calif) provides a biking action using a reclining bucket seat. Resistance is provided by a gear system with three settings, but revolutions per minute are not constant. The intensity of the exercise session is based on the patient’s ability to maintain a miles-per-hour pace for the

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Table 2.

Borg Scale for Rating of Perceived Exertion

prescribes for them.

In most cases, the goal of women in the last trimester of pregnancy is to modify the training protocol to maintain a level of fitness rather than to attempt to make improvements. The use of supervised exercise sessions is beneficial in quantitating individual work loads during each session. Each workout is a progression on the previous session, so improvements in total work capacity increase without causing undue stress on the mother or fetus (based on the woman’s perceived exertion rate; the fetus’s heart rate, which is monitored during and after selected exercise sessions; and the woman’s own self-monitoring, which is performed by palpating the abdomen for any sign of uterine contractions).

Role of Exercise

duration of the session, while keeping within her own target heart rate. The latest version of the recumbent bike includes hydraulic arm rowing devices for added resistance. The use of this added feature increases the muscle mass involved in the exercise, and raises the heart rate proportionally to the intensity of the pulling action. Patients’ progress on each machine is based on their functional work capacity, heart rate response to exercise, and perceived exertion based on the Borg scale’O (Table 2). After a few weeks of exercise, the same work load may be achieved with both a lower heart rate and a lower perceived exertion rate. Then the work load is increased until the target heart rate is up to an adequate training range. Although increases may be slight and sometimes not perceived by the patient, it is possible, with supervision, to make improvements with this

type of training. Exercise sessions may alternate among the aerobic machines to work different muscle groups and provide different types of exercise stimulus. All three machines offer the patient some degree of protection against jarring (and excessive movement) because they are not weight bearing in nature. The machines place little or no load on the lower extremities, and each provides different resistance settings to vary the workout intensity. Weight-bearing exercises may be associated with an increase in uterine activity, r2 thus nonweight-bearing exercises may be the modality of choice for women with GDM who (u) require direct supervision, (b) are exercising at a specific intensity, or (r) may have orthopedic limitations for weight-bearing exercises (such as obesity, lower limb edema, or a limited range of motion, etc). At the end of each workout session, patients obtain a postexercise blood glucose check so that the effect of exercise on glucose consumption can be ascertained.


From the standpoint of convenience, personalized training offers an alternative to other types of exercise training because it allows the pregnant woman to engage in physical conditioning outside of the classroom setting using alternative exercise modalities and environment to improve her level of fitness. Because the session is monitored by an individual who is trained to modify the workout in cases of distress, this type of training also enhances safety. Workout sessions may be interrupted or discontinued by a fitness specialist if he or she deems it appropriate. Table 3 highlights the advantages to pregnant women of using a supervised training program outside of the classroom. In terms of diabetes control, the exercise professional can aid newly diagnosed patients in properly executing blood glucose monitoring; explain how their increased metabulism (as a result of exercise) may be beneficial in keeping their blood glucose levels lower during the course of the day: adjust insulin levels downward as physical conditioning improves; and discuss physical and lifestyle changes associated with fitness, including lowering cardiovascular risk factors, better outlook on life, more 10 energy, more restful sleep, and so forth. Such topics can be discussed during the training sessions as part of the educational component. Fitness specialists who are knowledgeable about diabetes may conduct classes for fitness enthusiasts or train individual patients. They may contract their services to community or university fitness programs, and teach classes on different aspects of exercise as it relates to diabetes. With their knowledge about how exercise may help persons with diabetes improve metabolic control, the fitness professional can become an important part of a total diabetes management program.

Recommendations Women with GDM who wish


engage in aerobic

training to

Advantages of Supervised Training Program During Pregnancy

Table 3.

Response to Exercise Women who engage in supervised training sessions increase the level of fitness to whatever degree the exercise specialist Downloaded from tde.sagepub.com at FLORIDA ATLANTIC UNIV on May 24, 2015


improve fitness and diabetes control should be aware of a few basic ~

points: Try to exercise at about the same time every day. Regularly scheduled exercise is


effective in



of information and proper training protocols will be beneficial to everyone involved in exercise, from the fitness professionals to expectant mothers who wish to remain active throughout pregnancy.

glucose levels than is sporadic exercise. ~



Select aerobic machines that fit your body type and are comfortable to use. Know how to calculate your target heart rate and apply this knowledge to your exercise intensity during workouts. (An easy calculation for women is 220 minus your age times .65 to .75. Example: 220 - 25 x .65 to .75 = 127to 146 target heart rate. Staying within that training zone will assure that the intensity will give you a training effect without excessive fatigue.) Remember to drink water regularly so as not to dehydrate

yourself. ~



Follow these exercise session principles for proper prescription : frequency (3 to 4 days of exercise per week), intensity (regulated by target heart rate and RPE), and duration (length of the exercise session, usually 15 to 30 minutes of aerobic exercise). Discontinue any session if you experience signs of undue fatigue, labored breathing, excessive muscle soreness, or signs of hypoglycemia (dizziness, nausea, shaky hands, incoherent speech). Be sure to monitor blood glucose levels before and after each exercise session.


Pregnant women who wish to continue or start an exercise program represent a small but significant sample of the exercise community. Their special needs make them a challenge to the exercise specialist to provide prenatal care as well as a properly prescribed fitness program. The continued growth

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2. Leaf DA. Exercise and pregnancy: current concepts and controversies. Int Med 1985;8(7):185. 3. Artal R, Wiswell RA. Exercise and pregnancy. Baltimore: Williams & Wilkins, 1986. 4. American College of Sports Medicine. and exercise prescription. 2nd ed.


Guidelines for graded exercise Philadelphia: Lea & Febiger,

1980:18. 5. Beckwith KA. Exercise and pregnancy: is it safe? Ann Arbor: University of Michigan, 1984.

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6. Wolfe LA, Ohtake PJ, Mottola MF, McGrath MF. Physiological interactions between pregnancy and aerobic exercise. In: Exercise and sport sciences reviews. Vol 17. Baltimore: Williams & Wilkins, 1989:295-351. 7. Artal R, Wiswell RA, Romem Y. Hormonal response to exercise in diabetic and nondiabetic pregnant patients. Diabetes 1985:34(suppl 2):78. 8. Jovanovic-Peterson L, Durak EP, Peterson CM. Randomized trial of diet versus diet plus cardiovascular conditioning on glucose levels in gestational diabetes. Am J Obstet Gynecol 1989;161:415.

9. Olkin SK. Positive pregnancy fitness. Garden City Park, New York: Avery Publishing Group, 1987. 10. Borg G. Physical performance and perceived exertion. Lund, Sweden: Gleerup Publishers, 1982:1-63. 11 Cooper KH. The aerobics M. Evans & Co, 1982:125.

program for the total well-being.

New York:

12. Durak EP, Jovanovic-Peterson L, Peterson CM. In search of a safe exercise as potential treatment for gestational diabetes [Abstract]. Med Sci

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Physical and glycemic responses of women with gestational diabetes to a moderately intense exercise program.

Aerobic exercise machines are becoming more popular. Their use by women with gestational diabetes is reported, and their benefits in improving blood g...
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