Effects of walking speeds and durations on plantar skin blood flow responses

Background: Various walking speeds and durations in daily life cause different levels of ischemia of plantar tissues. It is unclear what walking speeds and durations significantly affect plantar tissue viability and risks for foot ulcers in non-diabetics and diabetics. Objective: The aim of this study was to establish the normal response of plantar skin blood flow to different speeds and durations of walking exercise in non-diabetics that would be needed to quantify impaired responses in diabetics. Method: Laser Doppler flowmetry was used to measure plantar skin blood flow of the first metatarsal head in 12 non-diabetics. A 3 × 2 factorial design, including 3 speeds (slow at 3 km/h, moderate at 6 km/h, and fast at 9 km/h) and 2 durations (10 and 20 min), was used in this study. Skin blood flow after walking was expressed as a ratio of skin blood flow before walking. The 3 × 2 two-way analysis of variance (ANOVA) with repeated measures was used to examine the main effects of speeds and durations and their interaction. Result: The walking speed significantly affected skin blood flow responses (p < 0.01). Walking at 9 km/h significantly increased plantar skin blood flow (5.71 ± 1.89) compared to walking at 6 km/h (2.1 ± 0.29) and 3 km/h (1.16 ± 0.14), especially at 20-minute walking duration (p < 0.01). The walking duration showed a trend of significance on affecting skin blood flow responses (p = 0.06). There was no significant interaction between walking speeds and durations (p > 0.05). Conclusions: Our results provide the first evidence that walking speeds affect plantar skin blood flow and a fast walking speed (9 km/h) significantly increases plantar skin blood flow compared to moderate (6 km/h) and slow (3 km/h) walking speeds.