Changes of SFA resting diameter Our main hypothesis was based upon the view that (i) endothelial shear stress is a main driver in adaptation of resting diameter in the conduit arteries and that (ii) vibration exercise will enhance endothelial shear stress. It is our opinion that the current data, although collected meticulously and with great care, do not provide strong enough evidence to put the first assumption into question because of the bulk of literature in
their support (Langille & O’Donnell, 1986; Tuttle et al., 2001;
Balligand et al., 2009). In many biological systems, however,
the frequency composition of a controlling signal is of great
importance, and it seems that considering the frequency composition
of shear stress imposed by arterial (= pulsatile) flow
could be relevant, too. In the light of this consideration, the
obvious conclusion from the present study would be that it
could be flow-mediated, rather than acceleration-induced
shear stress that matters for the adjustment of resting diameter.
On the other hand, this explanation would be at
variance with the aforementioned findings in the bed-rest
setting (Bleeker et al., 2005b; van Duijnhoven et al., 2010). Importantly, there is no substantial metabolic demand upon the immobilized leg musculature, and flow-mediated shear