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Lower Limb Dynamic Activity Significantly Reduces Foot Skin Perfusion: Exploring Data with Different Optical Sensors in Age-Grouped Healthy Adults

Introduction: The human lower limb is widely used as a model to study in vivo microcirculatory physiology and pathophysiology. It is a preferential target for critical comorbidities (overweight, diabetes, and peripheral vascular disease). Movement and activity are consistently regarded as beneficial, but the related adaptive physiology is still poorly understood. Our goal was to better identify the foot microcirculatory changes after a regular walking gait activity in healthy subjects of different ages. Methods: Twelve healthy participants of both sexes, with normal BMI and Ankle-Brachial Index, were selected and grouped according to age – group I (21.0 ± 1 y.o.) and group II (55.8 ± 3 y.o.). The protocol involved 2 phases of 5-min duration each – phase 1, a static standing position, and phase 2, 5-min walking with a comfortable pace on a pre-established circuit. Perfusion changes were assessed in the dorsal region of both feet before (baseline, phase 1) and after (phase 2) the gait period by noninvasive optical technologies – laser Doppler flowmetry (LDF), photoplethysmography, and polarized spectroscopy (PSp). Comparative statistics were performed with a 95% confidence level. Results: All instruments detected an asymmetric nonsignificant perfusion between right and left feet during rest in all participants with values in females consistently lower than men. Older participants exhibited lower baseline values than the younger group. Gait evoked a perfusion reduction in all participants relative to phase 1 detected with all technologies, with statistically significant changes recorded with LDF (group I, p = 0.033, and group II, p = 0.028) and PSp (group II, p = 0.041). Furthermore, LDF revealed that gait significantly reduced perfusion velocity in the older group (p = 0.003). Corresponding changes in the younger group were present but discrete. Recovery to baseline levels was also slower in the older group. Discussion/Conclusions: Our results confirm that perfusion is age dependent and demonstrate the clinical relevance of simple dynamic activities such as gait. This reduction of the dorsal foot perfusion occurs in depth, being more pronounced with the movement intensity, suggesting a wide application potential in early diagnostics as for rehabilitation.