Changing relationships between skin blood flow and arterial pressure in mild exercise and recovery

The beat-by-beat variability of heart period (RR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and skin microvascular conductance (G) in the palmar region of 23 healthy volunteers were analyzed during rest (R), clinostatic exercise at 10% maximum level (EXE1), 20% (EXE2) 30% (EXE3) and recovery (REC). G was obtained as the ratio between mean flow (laser Doppler) over one heart period and mean arterial pressure (Finapres). Exercise was accompanied by tachicardia, hypertension and skin vasoconstriction. Spectral analysis revealed an activation of the low frequency (LF, ∼0.1 Hz) in RR and SAP during EXE2 and EXE3. Recovery reestablished basal conditions in this regard. Vasomotor activity appeared as a LF component in G shifted at a lower frequency (∼0.7 Hz at R). At R SAP and DAP appeared pulled toward the vasomotor frequency compared to RR and this frequency change appeared to be enhanced by exercise. Conversely, during REC and uncoupling between systemic LF and vasomotor waves appeared. A comparison between the LF waves observed at the levels of heart, arteries and microcirculation appears a key element in understanding the role of vasomotion in the autonomic control of circulation and its responses to exercise.