Diabetes Mellitus and Exercise:What to Tell Patients

Your middle-aged patientwith type 2 diabetes wishesto start a weight-trainingprogram. What recommendationswill you offerhim? Another diabetic patient hasperipheral neuropathy; which exercisesare safest for her?Answers to these and otherquestions about physical activityby patients with type 1 and type 2diabetes mellitus can be found inguidelines from the American DiabetesAssociation.¹ Highlights ofthose recommendations arepresented here.EVALUATIONBEFORE EXERCISEBefore a diabetic patient startsan exercise program, a detailed historyand physical examination arerequired. Focus the evaluation onthe symptoms of diabetes that affectthe cardiovascular system andkidneys, as well as the nervoussystem.²Cardiovascular disease. Dependingon the intensity of the exerciseprogram that a patient wishesto pursue, a graded stress test maybe useful. If the exercise is low-intensity(less than 60% of maximalheart rate), such as walking, a stresstest may be appropriate if the patientis at high risk for cardiovascular disease(Table). If the intensity level isgreater--more than 70% of maximalheart rate--and there are underlyingrisk factors for cardiovasculardisease, an exercise stress test isrecommended.Patients who show nonspecificECG changes while exercising orwho have nonspecific ST- and Twavechanges on the resting ECGmight benefit from radionuclidetesting or an alternative test. In patientswith known coronary arterydisease, evaluate ischemic responseto exercise, ischemic threshold, andpropensity for arrhythmia. Assessmentof left ventricular systolicfunction at rest and in response toexercise is a valid option in manycases.Peripheral arterial disease.Signs and symptoms of peripheralarterial disease include intermittentclaudication, decreased or absentpulses, cold feet, atrophy of subcutaneoustissues, and hair loss. Ischemicchanges in the forefoot mayoccur even if dorsalis pedis and posteriortibial pulses are present. Ifyou have any doubts concerningblood flow to the forefoot and toesduring the physical examination,measure toe pressures and Dopplerpressures at the ankle.Retinopathy. Depending onthe degree of diabetic retinopathy,assess the amount and intensity ofexercise according to the risks involved.If the eye examination revealseither no diabetic retinopathyor moderate nonproliferative diabeticretinopathy, then all but extremeactivities, such as boxing and heavylifting, are acceptable. For patientswith active proliferative diabeticretinopathy, strenuous activity maycause vitreous hemorrhage or tractionretinal detachment. Low-impactactivities, such as swimming or stationarycycling, are acceptable, butjogging and weight lifting should bediscouraged.Nephropathy. Advise patientsto avoid strenuous activities; however,low- to moderate- level exerciseis acceptable. Patients withovert nephropathy frequently havea reduced capacity for exercise, andthey tend to limit their physicalactivity.Peripheral neuropathy. If apatient has lost protective sensationin the feet, any weight-bearing exercisewill carry a risk of ulcerationand fractures. If tests of deep tendonreflexes, vibratory sense, or positionsense suggest peripheral neuropathy--or if the 5.07 (10-g) monofilamentfails to indicate touch sensation--then jogging, treadmill exercise,and even extensive walkingshould be discouraged. Swimming, bicycling, and other non-weightbearingexercises would still beacceptable.Autonomic neuropathy. Cardiacautonomic neuropathy associatedwith diabetes has been linked tosudden death and silent myocardialischemia. An appropriate noninvasivetest to determine such risks isresting or stress thallium myocardialscintigraphy. Patients with autonomicneuropathy are more likely toexperience hypotension or hypertensionat the start of an exerciseprogram or after a vigorous session.Because these patients also havedifficulty with thermoregulation,they should not exercise in hot orcold environments and should drinkplenty of fluids regularly whileworking out.PREPARATION FOREXERCISEEncourage patients with diabetesto engage in physical activities.Young patients with good metaboliccontrol can participate in mostactivities. Middle-aged or older patients--after proper screening--canengage in many activities that arenot high-impact or high-resistance.Recommend both a warm-upand a cool-down period (5 to 10 minuteseach). During the warm-up,low-intensity aerobic activity is recommended. Stretching the musclesto be used in the exercise session isalso advisable, either during or afterthe warm-up. During the cool-down,the heart rate is gradually loweredto its pre-exercise level.Because trauma to the feet is arisk for patients with diabetes--particularlythose with peripheral neuropathy--recommend silica gel orair midsoles. Polyester or polyestercottonsocks can help prevent blistersand keep the feet dry. Tell patientsto monitor themselves for blistersand other injuries both beforeand after each session. They shouldalways wear a visible diabetes identificationbracelet or shoe tag whileexercising.Hydration, especially whenexercising in the heat, is essential.Recommend that patients drink17 oz of fluid 2 hours before exercising,and emphasize the need forearly and frequent hydration duringthe session.Although high-resistanceweight training is not recommendedfor older diabetic persons, nearly allpatients can benefit from moderateweight-training programs. Such programsuse light weights and a highnumber of repetitions to strengthenthe upper body and maintain goodmuscle, bone, joint, and ligamenthealth.TYPE 2 DIABETESAND EXERCISEStrongly encourage patientswith type 2 diabetes to participate inan exercise program--and the soonerthe better. Exercise may have agreater beneficial effect on metabolicabnormalities early in the progressionof diabetes, when patients showinsulin resistance or impaired glucosetolerance, rather than later,when they are experiencing overthyperglycemia. The specific benefitsof a long-term exercise program forpatients with type 2 diabetes include:

• Improved glycemic control.
• Reduced risk of cardiovasculardisease.
• Improved lipid levels.
• Reduced blood pressure.
• Weight control.

Glycemic control.

Althoughstudies are not conclusive, it appearsthat regular exercise helps patientswith type 2 diabetes improve theircarbohydrate metabolism and insulinsensitivity. For patients withimpaired glucose tolerance or uncomplicatedtype 2 diabetes, studieshave demonstrated sustained improvementsand few complications.

Prevention of cardiovasculardisease.

The insulin resistance syndromeis a key risk factor for prematurecoronary artery disease in patientswith type 2 diabetes. Thesepatients usually have a low level offitness and often have other cardiovascularrisk factors, such as hypertension,hyperinsulinemia, centralobesity, and dyslipidemia. Exercisecan help forestall cardiovascular diseaseby improving insulin sensitivityand thereby decreasing plasma insulinlevels.Regular physical training reduceslevels of triglyceride-richvery-low-density lipoprotein, butmost studies have not demonstratedpositive effects on low-density lipoproteinor high-density lipoproteincholesterol in patients with type 2 diabetes. Improvements in bloodpressure have been shown mostconsistently in patients who have hyperinsulinemia.Many patients withtype 2 diabetes have impaired fibrinolyticactivity, but so far no studyhas demonstrated that physicaltraining improves this condition.

Obesity.

When accompaniedby a calorie-restricted diet, exercisecan help patients lose or maintainweight. Studies have not focusedspecifically on patients with type 2diabetes, however, and much of theevidence is obscured by the concurrentuse of diets and other behavioralinterventions. Exercise mayhave an especially propitious effecton loss of intra-abdominal fat, whichhas been linked with metabolic abnormalitiesin diabetic patients.

Prevention of type 2 diabetes.

Exercise may help delay or evenprevent the onset of type 2 diabetes.Three trials have demonstrated delayor prevention of diabetes withlifestyle modification (regular moderatephysical activity and weightloss).

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TYPE 1 DIABETESAND EXERCISE

who have no complications and whohave good blood glucose control mayengage in all levels of exercise, fromleisure activities to competitive professionaltraining. Advise patients tomonitor their own blood glucose datain response to exercise; they canthen use this information to enhancetheir safety and performance (

Box

).Intensive insulin therapy has allowedpatients to adjust doses forthe appropriate activity. But adviseagainst the previously common practiceof using carbohydrate supplementswithout regard to glycemiclevels at the start of exercise. Thatpractice can actually neutralize thebeneficial effects of exercise onglycemic control.These guidelines for adultswith type 1 diabetes (and no complications)can be recommended forchildren and adolescents as well.The key factor is to regulate glycemiclevels while also maintainingthe young person's normal experienceof play. Hormonal changes inadolescents and greater variabilityof blood glucose levels in childrenmake such regulation more challengingbut still possible with carefulself-management and treatment ofhypoglycemia.

References:

REFERENCES:

1.

American Diabetes Association. Physical activity/exercise and diabetes.

Diabetes Care.

2004;27(suppl 1):S58-S62.

2.

Devlin JT, Ruderman N. Diabetes and exercise:the risk-benefit profile revisited. In: Ruderman N,Devlin JT, Schneider SH, Krisra A, eds.

The HealthProfessional’s Guide to Diabetes and Exercise.

Alexandria,Va: American Diabetes Association; 2002.

3.

Tuomilehto J, Lindstrom J, Eriksson JG, et al.Prevention of type 2 diabetes mellitus by changes inlifestyle among subjects with impaired glucose tolerance.

N Engl J Med.

2001;344:1343-1350.

4.

Pan XR, Li GW, Hu YH, et al. Effects of diet andexercise in preventing NIDDM in people with impairedglucose tolerance. The DaQing IGT and DiabetesStudy.

Diabetes Care.

1997;20:537-544.

5.

Diabetes Prevention Program Research Group.Reduction in the incidence of type 2 diabetes withlifestyle intervention or metformin.

N Engl J Med.

2002;346:393-403.