How do we deal with physical activity in people with diabetic neuropathy at risk of foot ulceration?

Offloading is one of the cornerstones of prevention of foot ulcers. The basic idea is easy: when there is no stress on the skin (i.e., when it is adequately offloaded), skin will not break down. Apart from adequate footwear, reducing physical activity seems another method to reduce the stress on someone’s foot. When a patient reduces their number of steps, there is less stress on their feet. However, if anything, physical activity generally needs to be increased in people with diabetes. This has led clinicians in the foot field with two extremely different options for years. Does your patient with diabetic neuropathy (at risk of foot ulceration) needs to increase or decrease their activity?

A new perspective paper will be published in the journal Physical Therapy in January 2017 postulating a new paradigm: stress on the skin should not be so high that it causes injury, but it should also not be so low that it reduces stress tolerance or causes atrophy. This interesting hypothesis is worth a closer look (and the full paper is worth a read over Christmas).

There is little debate on the first part, as that is in line with the offloading recommendations in international guidelines: high stress on the skin should be avoided. To prevent a foot ulcer, this level has been quantified in recent years as a 30% reduction compared to standard footwear, or as peak plantar pressures below 200kPa. The second part, however, is the new aspect of this paradigm: stress levels should not be too low. Unfortunately, there is very little evidence available to substantiate this part at the moment, which leaves room for discussion and critical thinking.

The most important research to back this is probably the “weight-bearing” trial, co-authored by one of the lead authors of this paper. This RCT found that a weight-bearing exercise program did not increase the risk of foot ulceration, showing that physical activity can be safely performed in this group of patients. However, the authors did not measure stress, so a “safe level” cannot be determined based on their results. Additionally, two high-quality studies from the US and the Netherlands indicate that daily activity itself is not a risk factor, but variation in daily activity is. This may indicate that consistent levels of higher stress are less harmful than sudden peaks in stress, because the skin will be less adapted to stress in the second instance.

Another, indirect, argument in favour of this paradigm is the age-old “use it or lose it” principle, which applies to so many parts of the body. Bones weaken when they are not put under stress, nerve functions deteriorate, physical fitness drops. It seems logical that a similar principle might apply to the skin; however, there is very little research to the quality of neuropathic skin to substantiate this. We therefore do not know when stress levels are “too low”, leaving clinicians with a hypothesized window of “good stress” that, at this moment, cannot be further substantiated or assessed.

The current paper does not provide the answer to the question whether to reduce or increase physical activity in your patients. It does, however, make two important suggestions that can (and perhaps should) be applied to clinical practice tomorrow:

• Do not be overly protective with regard to activity levels in people at risk of foot ulceration, but give them overload stresses
• Activity and stress need to be carefully monitored

The first suggestion is just as you would with any other population, with the goal of helping them to become more stress tolerant. The second may help to keep your patient below the level of “too much stress”, while still making sure they are active and profiting from physical activity.