Exercise for the patient with diabetes
Although aerobic exercise is recommended for patients with diabetes, an understanding of diabetic foot ulcer pathology, biomechanics, and adaptive footwear is needed in order to design an exercise program that is safe for patients who are at risk for developing diabetic foot ulcers.
Exercise for the patient with diabetes
Diabetic foot ulcers (DFUs) are by definition wounds that occur on the weight bearing surface of the foot or the dorsal digits as a result of repeated trauma, sensory neuropathy, and bony deformities. Other factors that can contribute to the failure of DFUs to heal include peripheral arterial disease, poor glucose control, inappropriate footwear, lack of adherence to the program, and activities that create pressure and shear at the site of injury. Standard care for these wounds is well documented to include debridement of necrotic tissue, treatment of infection, dressings for moisture balance, and OFF-LOADING to redistribute the pressure away from the injured tissue. The gold-standard for off-loading is the total contact cast, although numerous other methods have been used and found to be effective in promoting healing.
A critical part of managing diabetes is for the patient to be physically active, to exercise as part of a total program to control blood glucose levels, improve cardiovascular health, and maintain optimal function. One study showed that regular exercise reduces the cost of medical care for patients with diabetes. The National Institute of Health recommends 150 minutes of aerobic exercise per week for patients with diabetes. A review of exercise programs recommended for diabetes control that are available on-line revealed a variety that may not always be appropriate for the patient with sensory neuropathy, bony abnormalities, and risk for ulceration.
Traditionally increased peak pressures on bony areas was reported to be the main cause of DFUs. However, more recently plantar shear stress has been presented as a causative factor. Therefore any health professional prescribing an exercise program needs to assess both the patient’s feet and the risk of shear that may occur during the exercise routine. The DFU visualized in the photo is an example of one caused by shear, and it indeed looks much like a pressure ulcer described as deep tissue injury, which is known to be caused by shear. Shear differs from direct pressure which is defined as a direct vertical load on tissue. Shear stresses “act tangentially in anteroposterior and mediolateral directions at the foot-ground interface, transmitting a complex stress-strain pattern to the sublayers of the plantar tissue. These stresses are applied in alternating direction and are abrasive to the plantar surface, particularly during walking.” The stress occurs between the bone and the adjacent tissue causing disruption of the capillaries, bleeding into the tissue, and subsequent tissue necrosis. This pathological progression tends to lead to undermining and tunneling so that once the ulcer presents on the surface, one is only seeing the tip of the iceberg, so to speak.
With this risk of ulceration, what type of exercises are safe for patients with diabetes? The Cleveland Clinic lists 5 that it considers safe: walking, tai chi, yoga, dancing and swimming. My experience with patients and working through their exercise programs is that any exercise in a standing position that results in the foot being planted while the body moves over that base of support (e.g. squats, elliptical, rowing, treadmill walking) will produce shear between the subcutaneous tissue and the bony, weight-bearing prominences of the plantar foot. Safer exercises, especially for the high risk patient, include bicycling, upper extremity ergometer, weight exercises in a sitting position, and swimming. The problem with swimming is getting in and out of the pool barefooted, or walking on the bottom of a pool with a rough surface. The skin maceration that occurs with prolonged immersion in water can also be problematic. Any patient needs to be instructed in daily foot inspections, especially after exercising, to ensure that there is no tissue injury.
During any weight-bearing activities the patient is advised to use shear-reducing insoles and diabetic shoes. The Therapeutic Shoe Bill states that Medicare will cover 1 pair of custom-molded shoes and 3 pairs of inserts per year for the patient who has severe diabetic foot disease, provided the patient is being cared for by a physician who manages the diabetes. The combination of correct footwear and a prudent exercise program, prescribed by a knowledgeable health care provider who understands movement and the diabetic foot, is the best prevention for development of DFUs.
Further information on diabetes and the diabetic foot, the pathophysiology and resulting biomechanical changes, can be found at the following site:
Scarborough P, McGuire J. Diabetes and the diabetic foot. In Hamm R (Ed), Text and Atlas of Wound Diagnosis and Treatment: 2nd edition. New York: McGraw Hill Education. 2019, 199-233. Available at https://accessphysiotherapy.mhmedical.com/book.aspx?bookid=1334.
 Yavuz M, Ersen A, Hartos J, Schwarz B, Garrett AG, Lawrence AL et al. Plantar shear stress in individuals with a history of diabetic foot ulcer: An emerging predictive marker for foot ulceration. Diabetes Care. 2017;40(2):e14-e15.