Minimizing Risks in Patients Who Have Neuropathy

Sheila A. Ward, PhD, MPH

THE PHYSICIAN AND SPORTSMEDICINE - VOL 33 - NO. 8 - AUGUST 2005

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In Brief: Exercise is an important component of diabetes management that can help maintain physical fitness and help slow the development of peripheral neuropathy. However, because of impaired sensation, a person who has diabetic peripheral neuropathy risks developing infected foot ulcers when exercising. These infections can eventually lead to lower-extremity amputation. Clinicians who are familiar with techniques for preventing diabetic foot ulcers, foot ulcer risk factors, and strategies for exercising safely with diabetes and insensate feet can provide foot care guidelines for patients with diabetes who exercise.

Diabetes, the sixth leading cause of death in the United States, accounted for more than 71,000 deaths in 2001.¹ As many as 18 million people in the United States have diabetes, but more than 5 million people remain undiagnosed.²

Patients who have diabetes may experience many long-term complications, such as nephropathy, neuropathy, and retinopathy. Diabetic neuropathy, a leading cause of foot ulceration, is estimated to affect 15% of all persons with diabetes at some time during their lives.³ Diabetic foot ulcers and lower-extremity amputation are recognized as major public health issues and were included in the Healthy People 2010 initiative.⁴ Diabetic foot ulceration accounts for 83% of the $10.91 billion annual cost to treat diabetic peripheral neuropathy and its complications.⁵

The goal of diabetes management is to maintain a near-normal blood sugar level by carefully coordinating diet, exercise, medication (if necessary), and glucose monitoring. Diabetic complications are best delayed or managed by normalizing the glucose level and by managing cardiovascular disease risks factors, such as hypertension, a common comorbidity of diabetes.⁶

Exercise is an important component of diabetes management. As with any exercise program, the benefits should outweigh the risks. This is especially true for patients who are at high risk for foot ulceration, because diabetic foot wounds are the most common foot complication that leads to amputation. Patients who have diabetes also need to take precautions, such as wearing appropriate footwear, so that new foot ulcers do not develop while they are exercising. Using a team approach involving the patient, exercise specialist, and primary care physician ensures proper foot care and footwear, prevents foot ulcers by understanding and recognizing risk factors, and encourages diabetic patients to exercise safely.

Origins of Foot Ulcers

Diabetic foot ulcers are a major reason why people with diabetes are hospitalized.⁷ Because neuropathy often accompanies these open sores, patients are unable to feel pain. If foot ulcers become infected, gangrene and amputation can result. If the ulcers are detected early and treated appropriately, up to 85% of amputations can be prevented.⁸

A foot ulcer is diagnosed by a physician during a comprehensive wound evaluation. Foot ulcers, frequently covered by callous tissue, commonly form over the metatarsal area or the top or tip of a toe. They may be caused by pressure from improperly fitted shoes, a corn or callus, or an injury such as a splinter. Continued pressure on an open injury may cause infection, leading to gangrene and amputation.^6,7 Foot injuries and diabetic foot ulcers can be caused by intrinsic factors (eg, loss of sensitivity, reduced proprioception, abnormal foot shape) or extrinsic factors (eg, tight shoes, rocks, heat).

Prominent metatarsal heads are a key marker for the high-risk neuropathic foot, because ulceration occurs most frequently over these areas.⁷ In a normally structured and sensate foot, weight is evenly distributed across the metatarsal heads and constantly transferred from areas of pressure during walking and running.⁹ Muscles in the feet can atrophy and weaken, changing the bone-to-tissue ratio, structure, and shape of the foot. Any of these abnormalities are risk factors for foot ulceration.

Neuropathy

The main complications of diabetes that lead to foot ulceration are neuropathy and peripheral vascular disease. Autonomic neuropathy affects blood flow and reduces sweating, causing dry skin that cracks easily.¹⁰ Peripheral neuropathy contributes greatly to foot ulcers by causing a loss of or reduction in protective sensation, muscle strength, and balance. An estimated 30% to 65% of patients with diabetes have peripheral neuropathy to some degree.¹¹ A high risk of future ulceration has also been suggested in patients who have motor neuropathy.¹² Exercise can increase blood flow to affected areas and help slow the rate of peripheral neuropathy development by reviving motor nerve function and preserving unaffected motor nerves. Exercise helps maintain physical fitness through improved muscle strength, flexibility, tone, and balance.¹³ Patients who have diabetes can prevent or lessen nerve damage by keeping blood glucose levels close to normal, not smoking, not drinking too much alcohol, managing blood pressure and cholesterol levels, and having an annual foot exam.

Exercises for Patients With Neuropathy

Whether beginning an exercise program or transforming a regular exercise program into a more vigorous regimen, patients with diabetes must have medical clearance.¹⁴ Walking is recommended for beginning exercise programs, because it is easy, safe, and accessible. However, walking is a weight-bearing activity, and footwear and walking surfaces are important safety factors.

Exercises that do not put much stress on the feet and weight-bearing joints are recommended for patients with diabetes who have a loss of protective sensation. These exercises include swimming, bicycling, rowing, and other non–weight-bearing exercises and a variety of upper-body exercises, including chair and arm exercises.¹⁴ Weight-bearing activities, such as using a treadmill, prolonged walking, jogging, and step exercises, are absolutely not recommended for patients with active foot ulcers. Patients with diabetes and peripheral neuropathy or previous foot ulceration may need to reduce or avoid these activities as well.¹⁵ Non–weight-bearing exercises (eg, chair aerobics, arm ergometry) are recommended for patients with active foot ulcers who want to exercise during the healing process. Patients who have open wounds should not exercise in a pool until the wounds are completely healed.

Prescribing weight-bearing exercises for patients with peripheral neuropathy requires a great deal of consideration. Pain is often present in peripheral neuropathies, but not in all cases. The missing sensation of pain, when it should be present, can be dangerous for the sedentary diabetic patient and even more dangerous for the active patient with diabetes. The ability to feel pain protects the foot, because patients are alerted to conditions that may become serious.

Diabetic patients with peripheral neuropathy and insensate feet may choose to participate in weight-bearing activities, and more research is needed to determine the safest activities for them.¹⁶ It is important that physicians work with their patients' attitudes and behaviors toward proper foot care, footwear, and the types of exercises they participate in when they are diagnosed with insensate feet.

Effective communication between the patient and the clinician will help the patient understand the roles of the sensory feedback system and "pain" (see "Foot Care Guidelines for Patients Who Have Diabetes"). The sensory feedback system enables the body to respond to discomforts or irritations before pain receptors are activated. These warnings allow the body to make needed adjustments to avoid putting excess stress on the foot that could lead to bone damage or breaks in the skin. Instead of becoming emotionally detached from their feet,¹⁷ patients with insensate feet must learn to rely on other sensory modalities, such as the eyes to check for discoloration, bruises, or cuts that may have been caused by objects in the shoes, the fit of the shoes, or movement.¹⁸ Hand inspection to check for irregularities in footwear is crucial.

A qualified exercise specialist is a very important team member in the care of patients with diabetes. The exercise specialist understands the science of how the body responds to exercise and designs a specific exercise program for the special needs of diabetic patients. The exercise specialist should communicate with the physician as well as the patient to understand important risks factors in designing an exercise program that is safe and effective. The American Diabetes Association recommends that qualified exercise specialists have a masters or doctoral level degree in exercise physiology or be licensed healthcare professionals who have received graduate-level training in exercise physiology.¹⁹

Preventing Diabetic Foot Ulcers

Identifying patients at high risk for foot ulcers is an important step in minimizing exercise risks. Patients must understand that prolonged high blood sugar levels can damage nerve cells and blood vessels that supply vital information and materials to the feet. Daily foot care and proper management of minor foot injuries (eg, cuts, scrapes, blisters, and, particularly, wounds that do not heal rapidly) and infections (eg, athlete's foot) can reduce the incidence of foot ulceration in diabetic patients who have neuropathy.²⁰ Even minor injuries must be given the utmost attention. Risk factor recognition, preventive foot maintenance, and regular foot examinations may be learned through a good ulcer prevention program.^8,15

In addition to neuropathy and peripheral vascular disease, common risk factors for diabetic foot ulcers include previous ulcer, structural changes in foot and callus formation, skin changes, abnormal gait, long duration of diabetes, smoking history, high hemoglobin component HbA1c, and low ankle-to-brachial index. Physicians should stress that keeping blood glucose levels as close to normal as possible slows the progression of diabetic foot ulcers.

Risk Factors and Shoes

Many aerobic activities, like walking and jogging, require appropriate footwear. Improper footwear may cause abnormal foot pressures, inadequate blood flow or ischemia, and inflammation from repetitive stress that may result in wounds or ulcers through the skin. If the ulcer gets infected and the patient does not detect it, he or she will continue walking and spread the infection deeper into the foot. The infected area will demand more blood than the reduced blood vessels can supply. Bone may also be lost to the point where the foot is inadequate for walking and bearing weight. The patient may need complete rest in a plaster cast to heal the neuropathic ulcer,¹⁸ and this can be challenging for a physically active person. Reducing foot ulcer risk factors may prevent such challenges.

Footwear is perhaps the most important gear when exercising, especially for the high-risk patient with diabetes. Appropriate footwear protects the skin and can reduce ulcer recurrence.²¹ In addition to wearing thick-soled shoes, patients who have sensory losses should always check for objects that may have fallen undetected into their shoes before placing them on their feet. Hot sidewalks, pool areas, heaters, or even hot baths can be damaging and cause severe burns on the feet. Special footwear is available for pool areas and swimming.

Orthotic management is also vital. Neuropathy combined with several forefoot structural deformities has been identified as a factor in increased plantar pressures.^22,23 The range of motion of the first metatarsophalangeal joint and the joint angle (ie, hammer toe deformity) are important indicators for determining pressures under the hallux. Orthoses can redistribute and reduce plantar foot pressures and help reduce the skin breakdown that may lead to ulceration.

For aerobic activity, the American Diabetes Association recommends reducing foot injury by using silica gels or air midsole orthoses and polyester or cotton-blend socks to prevent blisters and keep feet dry.¹⁹ Orthoses should be used to resolve fitting issues, new shoes should be broken in gradually, and worn-out shoes should be discarded. Socks should provide extra cushion and wick sweat away from the skin. Clean, dry socks should be worn at the start of each new workout, and sweaty socks should be removed at the end of each workout. Feet should be thoroughly dried after activity. Sweaty socks can be dangerous, because they increase the risk of athlete's foot.

Additionally, patients should select athletic shoes that are made for the type of exercise that will be performed, such as basketball, soccer, tennis, walking, aerobics, or jazz dance. The exercise surface, such as asphalt, carpet, or hardwood, should also be considered in athletic shoe selection. Exercise-specific shoes are designed to allow the safest and most efficient performance. For example, compared with court shoes, running shoes have more cushion, are flared to provide a broader and more stable base at the heel, and have a deep-cut tread that grips a variety of surfaces. Court shoes are designed to enable quicker side-to-side movements. Aerobic shoes have flatter tread and may have a round design under the ball of the foot for easy turning.²⁴ Primary physicians or podiatrists should check their diabetic patients' exercise footwear.

Abnormal stresses on the foot can trigger high- and low-pressure injuries that may result in foot ulceration. The soles of the feet are tough and designed to withstand much pressure without breaking or tearing. However, with neuropathy and a loss of pain sensation, sharp objects as small as a pebble can cause plantar pressure to rise high enough to break the skin. The irritant may remain embedded without the patient's awareness.¹⁸ A previous foot ulceration increases the risk of future injury, because both the foot dynamics and distribution of plantar pressures may change. Changes in gait caused by muscle atrophy or from a sprain or strain may cause new pressure points to form.¹⁵

Inadequate blood flow caused by tight shoes is a common cause of low-pressure injury. When trying on shoes, patients who are unable to feel the normal sense of shoe support may assume the shoe is too loose and ask for a tighter shoe. A tight shoe is dangerous, because ischemic pressure sores can occur on the edges of the feet where the fabric of the shoe bends.¹⁸ Shoes that are too tight can prevent continuous blood supply to the feet. Patients need shoes that have plenty of room around the forefoot and toes, but shoes should have a snug fit around the heel to prevent rubbing and blister formation. Leather is also preferable to plastic, because leather will conform to the foot and allow the foot to "breathe."

Repetitive Stress and Inflammation

Walking, jogging, and running produce repetitive stress, a common cause of ulceration. Repetitive stress causes a gradual buildup of inflammation with edema and other materials that stiffen the tissue in the sole of the foot.¹⁸ Because the tissue is less pliable, localized stress becomes more severe than in the normal sole. The normal sensate foot will experience discomfort from the irritation and use this as a sign to stop the activity. Patients who have insensate feet may continue to exercise and further damage their feet. Local warmth is the most consistent sign of developing inflammation; therefore, feet should also be checked for uneven temperatures that may indicate tissue breakdown in any part of the foot.

Foot Care Guidelines for Active Patients

Because weight-bearing exercise may pose great risk for foot problems, such as foot ulcers, proper foot care cannot be overemphasized for active patients who have diabetes. Minor cuts, scrapes, and bruises that occur during exercise cannot be ignored and should be examined by a physician. Strict observance of foot care guidelines for active patients who have diabetes can reduce the risk of injury or ulceration that can lead to infection and, possibly, amputation. Patients who have diabetes must understand that even minor infections can lead to very severe consequences, such as gangrene. Foot care education and appropriate exercise will ensure that the benefits outweigh the risks.

References

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2. Centers for Disease Control and Prevention: Section 2: The burden of heart disease, stroke, cancer, and diabetes, United States, in The Burden of Chronic Diseases and Their Risk Factors: National and State Perspectives 2004. Available at http://www.cdc.gov/nccdphp/burdenbook2004/toc.htm. Accessed April 11, 2005
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4. National Institutes of Health: Healthy People 2010. Bethesda, MD, US Department of Health and Human Services, 1999. Available at http://www.healthypeople.gov. Accessed February 22, 2005
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Foot Care Guidelines for Patients Who Have Diabetes Clinicians may use the following recommendations as an outline for discussions with their patients who have diabetes.1,2 For General Diabetes Care •Obtain medical clearance before starting any exercise program. •Report any injury, no matter how minor, before it can progress to a major complication. •Have a healthcare professional inspect your bare feet at every office visit. •Follow clinical recommendations for foot care, including an annual comprehensive foot exam. •Maintain good long-term control of blood glucose (blood sugar) levels and hypertension (high blood pressure) to prevent diabetic complications, such as peripheral neuropathy (nerve damage in your feet). •Do not smoke. When Buying Shoes •Select shoes that are made for the specific type of exercise that will be performed (for example, walking shoes, running shoes). •Check with a podiatrist to confirm the correct fit and see if orthotic inserts are needed. •Buy shoes that are comfortable when being fitted. Do not expect shoes to become more comfortable after you have worn them. •Gradually break in new shoes by wearing them for short intervals, then observe your feet carefully before wearing the shoes for longer periods. Small skin discolorations or indentations caused by fabric or shoelaces may be indications of pressure points (figure A). Before Putting on Shoes and Socks Each Time •Wear socks to provide extra padding for the bony parts of the feet. Socks should be smooth, provide cushioning and warmth, and wick sweat away from the skin. •Inspect socks for ridges, holes, or seams that may rub the foot and cause blisters, before gently putting on the socks. •Shake each shoe to check for foreign objects. Something could have fallen in unnoticed between wearings. •Use your hand to feel inside each shoe for a torn lining or lumpy insole. When shoes are worn out, throw them out and buy a new pair. General Foot Care •Wash feet daily in warm (not hot) water, but do not soak them. Soaking may soften the skin too much, increasing the likelihood of infection. •Carefully dry feet to remove excess moisture, especially between the toes. •Check feet daily for scratches, corns, and calluses, and again after exercise for any cuts, scrapes, blisters, or bruises that may have developed. If your vision is limited, ask a family member or friend to assist you. •If skin is very dry, apply moisturizer. Skin that is too dry can crack easily, creating an entry point for infection. •Prevent ingrown toenails by filing—not cutting—straight across the top and diagonally at the corners of the nails. Rounded or U-shaped nails are more prone to become ingrown. •If ingrown toenails, calluses, or corns develop, discontinue exercise and see a doctor right away. Do not try to use over-the-counter products to self-medicate. Special Exercise Precautions •Start off with a dry pair of clean socks each time you exercise, even if you exercise several times on the same day. •Never walk around barefoot, especially while exercising. Locker rooms, showers, and pool areas may harbor athlete's foot fungus or other infections, or you may accidentally step on a sharp object. •Avoid walking on hot surfaces, such as sidewalks or pool decks. •Do not use adhesive tape on your feet. •When exercising, make sure you drink enough fluids, monitor your blood glucose for unexpected changes, and have insulin and carbohydrates available. •Wear a diabetes identification bracelet so that appropriate help, if needed, may be provided. REFERENCES Levin ME: The diabetic foot, in Ruderman N, Devlin JT, Schneider SH, et al (eds): Handbook of Exercise in Diabetes, ed 2. Alexandria, VA, American Diabetes Association, 2002, pp 385-399 Coleman WC: The diabetic foot, in JK Davidson (ed): Clinical Diabetes Mellitus: A Problem-Oriented Approach, ed 3. New York City, Thieme, 2000, pp 571-580

Dr Ward was a research associate at the Strelitz Diabetes Institutes of Eastern Virginia Medical School in Norfolk and is currently an evaluator and exercise consultant with the division of Chronic Disease Prevention and Control at the Virginia Department of Health in Richmond. Address correspondence to Sheila A. Ward, PhD, MPH, Norfolk State University, Echols Hall, Rm 167, 700 Park Ave, Norfolk, VA, 23504; address e-mail to sward@nsu.edu.

Disclosure information: Dr Ward discloses no significant relationship with any manufacturer of any commercial product mentioned in this article. No drug is mentioned in this article for an unlabeled use.