Considering the Optimal Approach to Physical Activity After Diabetic Foot Ulceration

Podiatrists frequently encounter questions about return to activity. After an injury in a healthy individual, we can usually answer this confidently. We gradually encourage activity to eventually meet the World Health Organization recommendations of 150 minutes a week of moderate-intensity aerobic physical activity, even among those with chronic conditions.¹ However, return to activity instructions are much less straightforward after a diabetic foot ulceration or partial foot amputation. On the one hand, activity and exercise are well known to have many health benefits for those with diabetes.² On the other hand, increased activity may elicit concern for ulcer recurrence.

Some patients are not motivated or are unable to improve their health due to frequent recurrent ulcerations or other health limitations. For this cohort, returning to baseline activity or merely meeting the minimum activities of daily living may, unfortunately, be the end goal. Others recognize the dangers and heed warnings of increased mortality associated with ulcerations.³ Even small amounts of activity can make a difference. In patients with diabetes, walking 2 hours a week demonstrated a 39% reduction in all-cause mortality and 34% in cardiovascular mortality.⁴ Although this study suffered from a possible selection bias, this effect remained even after controlling for insulin status, diabetes duration, heart trouble, and history of stroke.⁴

Other studies have also reported similar findings in patients who started cycling. In a large, multicenter 5-year prospective study of individuals with diabetes, study participants who took up cycling after the start of the study had a substantial reduction in a multivariate-adjusted hazard ratio of all-cause mortality (0.65, 95% CI, 0.46-0.92) compared to those who did not pick up cycling.⁵ A recent systematic review and meta-analysis has also found the benefits of even low-dose physical activity in patients with diabetes and demonstrated a nonlinear dose-response pattern across not only diabetes but multiple diseases.⁶

Aside from mortality, exercise training may lead to a reduction in HbA1c of about 0.8 ± 0.3%, similar to long-term drug or insulin therapy.⁷ Physical activity may even have a beneficial effect on depression in those with diabetes,⁸ which is known to be prevalent in this population.⁹ However, in higher-risk individuals, one should discuss health considerations such as hypoglycemia or cardiovascular conditions, which warrant modifications to the exercise plan, with the primary care provider and other appropriate physicians. Providers may consider reviewing the American Diabetes Association position statement for a brief overview.² Frequently, the primary physician has already recommended exercise and the patient is pending release to exercise from the podiatrist concerning the healed ulceration.

Is Physical Activity Safe for Those With Previous Ulcerations?

This is a difficult question to answer. Physical activity and exercise encompass many activities with varying degrees of demand on the foot. Excessive stress to the foot, referred to as plantar tissue stress, consists of all mechanical stress accumulated over time, including plantar pressure, shear stress, daily weight-bearing activity, and time spent in prescribed interventions.¹⁰ Interestingly, sedentary behavior has an association with ulceration development, contrasting the previous dogma that reducing activity will reduce recurrence.¹¹ Others have found that increasing daily weight-bearing activity did not increase reulceration rates.¹²

Armstrong and colleagues also found lower activity in those who ulcerated but found that individuals who ulcerated had greater activity variability.¹³ Thus, they suggested that one might implicate the peaks and valleys from mean daily activity in ulcer recurrence. However, step count is an incomplete picture of the overall weight-bearing activity. Patients with diabetic peripheral neuropathy spend twice as much time standing as walking.¹⁴ Accordingly, as Lazzarini and team describe, plantar tissue stress may be altered by various weight-bearing activities, such as standing, turning, and walking at different speeds. Steps alone do not reflect these types of activities.¹⁰ This makes measuring plantar tissue stress difficult and, in turn, the specific limitations of each respective and cumulative effect of activities challenging to prescribe.

Most regard a gradual increase in activity over time as sound advice. Presumably, a proper stimulus/stress should lead to adaptive changes over time and improved tolerance as described by “physical stress theory.”¹⁵ This principle is broad-ranging and applicable to many different problems. Most intuitively, there are applications in sports medicine in which athletes intentionally stress their bodies to allow for positive adaptations in their respective sports. However, too much applied stress can result in overuse injuries, and little or no stress over time can result in deconditioning or atrophy.

One can apply this concept to the skin of the plantar foot, but the theory assumes normal physiology, which is not a given in patients with previous foot ulcerations. Systemic conditions may result in a narrower therapeutic range with a lower injury threshold. Unfortunately, neuropathy makes it less likely that a patient will recognize that plantar tissue stress may be over this elusive threshold. Thus, one must exercise caution to gradually increase the plantar tissue stress over a longer duration. The specifics of how to do this are not known. A traditionally used guideline is a weekly increase of no more than 10% duration/distance in endurance sports.¹⁶ It may be prudent to progress slower than this, but this is merely a guess meant to temper my patients’ expectations and is without any robust evidence.

Some authors have taken physical activity one step further and evaluated exercise in patients with active ulcerations. A recent systematic review of 3 randomized controlled trials of non-weight-bearing exercise interventions with active ulcers found some promising results, but warned of methodological concerns and thus found insufficient evidence to support wound healing improvements with exercise.¹⁷ A scoping review of physical activity in patients with active ulcerations found similar results when expanding criteria outside solely randomized trials.¹⁸ Although not within the scope of this article, others undertook this investigation with venous ulcerations, but again, more evidence is necessary.¹⁹

Final Thoughts

Future studies may change our understanding, but it appears too early to recommend exercise with active ulcerations. There is, however, clear evidence of health benefits from physical activity and exercise in patients with diabetes. Some evidence also suggests that physical activity in patients that have healed foot ulcerations does not actually increase recurrence. It may be that purposeful, gradual increase in activity may counterintuitively reduce recurrence by increasing plantar tissue stress reserve, but we have to wait for future studies. For now, the possible neutral effect to healed ulcerations combined with the numerous health benefits associated with increased physical activity should encourage providers to recommend slowly increasing physical activity and exercise such as cycling while carefully monitoring their feet.

Dr. Thorud is a Fellow of the American College of Foot and Ankle Surgeons and practices in McHenry, IL.

References
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