Studying the in vivo microcirculatory adaptation to isometric contraction (dorsiflexion) in the human lower limb

Blood flow in the lower extremities varies considerably due to changes in pressure from muscle contraction as occurs with calf muscle pump activity. The dorsiflexion is associated with functional walking performance, and its relation with microcirculation of lower limbs has not yet been addressed. In this study we explore the impact of dorsiflexion in the lower limb microcirculation with non-invasive technologies, as near as possible to the normal physiological state. Six (31 9 years) healthy subjects were enrolled in this study after informed written consent. The experimental protocol consisted of 5 minutes standing, 1 minute of dorsiflexor muscle group contraction, and 5 minutes recovery in the initial position. Microcirculation was evaluated by photoplethysmography (PPG) and laser Doppler flowmetry (LDF). Pulse rate (PR) was obtained from PPG. Nonparametric statistics were used for phase comparisons. Dorsiflexion significantly modified the local perfusion, with PPG registering a decrease (p=0.028) while LDF registered an increase (p=0.028). PR did not change during the procedure. Foot dorsiflexion seems to cause different responses in the skin microvascular networks which might be attributed to the different measuring depths of the techniques employed, justifying further studies.