Association between daily steps and calf muscle oxygen saturation in patients with symptomatic peripheral artery disease

We determined whether patients with peripheral artery disease (PAD) who walked at least 7 000 steps/day had better microvascular function, assessed by calf muscle oxygen saturation (StO 2 ), and more favorable vascular biomarkers than patients who walked less than 7 , 000 steps/day. Five hundred sixteen patients were assessed on daily ambulatory activity for one week with a step activity monitor and were grouped according to whether they walked fewer than 7 , 000 steps/day (Group 1; n = 306) or for 7 000 steps/day or greater (Group 2; n = 210). Exercise time to reach the minimum calf muscle StO 2 was longer ( p = 0.025) in Group 2 ([297 ± 339] s) than in Group 1 ([210 ± 232] s). Additionally, high-sensitivity C-reactive protein (HsCRP) was lower ( p < 0.001) in Group 2 ([4.0 ± 4.5] mg/L) than in Group 1 ([6.8 ± 10.7] mg/L). In multivariable linear regression models, exercise time to minimum calf muscle StO 2 was associated with physical activity group status after adjusting for ankle/brachial index (Model 1) ( p = 0.032), and after adjusting for age, race, sex, education, and body mass index (Model 2) ( p = 0.044). HsCRP was associated with physical activity group status after adjusting for Model 1 ( p < 0.001), Model 2 ( p < 0.001), and the two models combined (Model 3) ( p < 0.001). Walking at least 7 000 steps/day was associated with better microvascular function in the calf muscle during exercise and with lower vascular inflammation in patients with symptomatic PAD. The clinical significance is that community-based walking for at least 7 000 steps/day is a simple goal that is associated with more favorable vascular outcomes in patients with symptomatic PAD.