Abstract
Ten healthy male subjects performed single (<1 s), sustained and intermittent plantarflexions
(up to 40 s) of one foot in sitting exercise position. Two different absolute forces
were applied, which, in terms of maximal voluntary contraction, ranged between 5%-10%
and 25%-30%. Blood velocity was continuously recorded in the proximal arteria femoralis
by means of the Doppler technique. Heart rate (HR) and mean blood pressure (BP) were
simultaneously determined using standard ECG and the FINAPRES™ method. Despite the
distance between the proximal arteria femoralis and the exercising muscle the Doppler
data showed: effects of single contractions on the individual Doppler data, the influence
of consecutive contractions, variation with exercise intensity and differences between
sustained and intermittent contractions. In all exercise tests there was an immediate
significant increase in blood velocity at the onset of exercise. The major part (range
52%-73%) of the response to the 40 s tests was seen during the first 6 s. It was followed
by a second phase of adjustment which depended on the type of exercise and exercise
intensity. The single plantarflexion provoked increases in blood velocity for about
20 s. A comparison of HR and BP tracings with the Doppler data demonstrated the importance
of local mechanical factors for the perfusion of the exercising muscle. The early
adjustment of muscle perfusion were not correlated to the systemic blood pressure
and, therefore, appeared to be related to muscle pump effects. The subsequent flow
values were influenced by passive vessel compression and changes in local vasomotor
tone. A fast withdrawal of vessel compression, refilling of veins and a slow readjustment
of vasomotor tone determined the post-exercise flow kinetics.
Key words
Muscle pump - muscle perfusion - exercise - humans - Doppler measurements
