January 2015

Out on a limb: Muscling in on diabetes

1Limb-JordanaJordana Bieze Foster, Editor

There are already plenty of good reasons for indivi­duals with diabetes to exercise. But here’s one more: Strengthening the intrinsic foot muscles just might reverse the development of diabetic peripheral neuropathy (DPN) even before it becomes clinically apparent.

Multiple studies have established that patients with DPN demonstrate significant intrinsic foot muscle atrophy compared with healthy controls. But new research is revealing that patients who have diabetes but do not have DPN also have significant intrinsic foot muscle atrophy relative to controls. A study from India, epublished in December by the Journal of Diabetes, and a study from China published in August by the online Journal of Diabetes Research, both arrived at similar conclusions.

The presence of intrinsic muscle atrophy in the absence of clinically detectable peripheral neuropathy supports the theory that the earliest stages of the DPN spectrum occur at a sub­clinical level. And that means clinicians shouldn’t have to wait until a patient presents with significant sensory loss to start taking steps to reduce the risks of ulceration and amputation.

Ideally, it also means interventions targeted at DPN specifically can be implemented even earlier. And it suggests that at least one aspect of those interventions should include exercises to strengthen those atrophied intrinsic foot muscles.

Few studies have looked at the effects of exercise on lower extremity-specific variables in patients with DPN—at least in part because it wasn’t until recently that research confirmed the loads involved in exercise would not, as many feared, increase the risk of neuropathic ulceration (see “Exercise and neuropathy: Not mutually exclusive,” July 2011, page 22). But, in a Brazilian study published in April 2014 by the online journal BMC Musculo­skeletal Disorders, a 12-week multimodal physical therapy program was associated with significant improvements in both intrinsic foot muscle function and Michigan Neuropathy Screening Instrument scores in patients with DPN.

So there’s at least some reason to believe that strengthening could have an independent positive effect on neuropathic symptoms in patients with DPN. And, if that’s the case, it’s certainly plausible that strengthening interventions in patients with subclinical DPN—those with intrinsic muscle atrophy—could help delay or prevent the clinical emergence of those symptoms.

The authors of the Indian and Chinese studies both suggested that musculoskeletal ultrasound could be used to screen patients for intrinsic muscle atrophy. To me, while ultrasound makes sense as a research tool, it doesn’t seem practical or cost-effective to use it to regularly screen every patient with diabetes.

But, if researchers can identify the point in the DPN spectrum at which muscle atrophy typically becomes apparent (in the Chinese study, the duration of diabetes in the no-DPN group was six years, so that’s a start), then it would make sense to screen patients with diabetes starting at that time. Or it might make sense to simply implement foot-specific exercise programs at that time point for all patients with diabetes, even without the formality of screening.

It’s no secret that early intervention is the key to prevention. Now clinicians who treat patients with diabetes can take that philoso­phy to the next level.

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