The acute effects of physical activity on the stiffness of the plantar skin of people with and without diabetes
Wendland, Deborah Michael
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Diabetes affects 25.8 million Americans. Complications related to this growing disease impact public health. One secondary complication of diabetes is changes in skin that can contribute to an increased risk for ulceration. Skin of people with diabetes has not been characterized over time nor has the skin’s acute response to exercise been assessed. The objective of this project was to establish the changes in skin properties over time, within different ambient environments, and after acute exercise. This objective sought to address the central hypothesis that skin will demonstrate decreased stiffness and increased elasticity as a result of acute physical activity. Skin stiffness, compliance, and thickness measurements of the plantar foot were compared across time and environment. Skin stiffness and compliance were also compared before and after treadmill walking. First, three devices were validated. Accuracy of the StepWatch was validated for people using assistive devices. The tissue interrogation device (TID), a novel device that measures tangential skin stiffness, and the myotonometer, which measures skin compliance, were validated using elastomer phantoms. Both were found suitable to measure plantar skin properties. Second, skin properties of 16 persons with and without diabetes were measured over time and environmental condition. Skin was variable across subjects over time, but was stable within subjects over a month, supporting the use of a repeated measures approach to interventional study on the plantar skin in people with diabetes. Previous findings for general skin characteristics were supported including the tendency for persons with diabetes to have a thinner epidermis and a thicker dermis than persons without diabetes. Tangential skin stiffness was determined to be less stiff in people with diabetes when measured in a medial-lateral direction. People with diabetes had lower tissue compliance than those without. Skin properties varied across environmental condition, supporting the consideration of testing environment when evaluating skin. Finally, changes in skin properties were evaluated in 32 persons with diabetes before and after treadmill (TM) walking. Using the TID, skin stiffness (tangential) at the great toe of people with diabetes (663.705±4.796 N/m) and without (647.753±5.328 N/m) were different (p=0.040). Stiffness immediately following TM walking did not differ from pre-walking stiffness, but subsequent trials had increased stiffness. Similar, but not significant responses were noted at the first metatarsal head. Compliance using normal loading increased after walking with statistical differences lasting 30-60 minutes.