For single tetanic contractions of 100, 250, 500, or 1000 ms duration at 100 Hz (key applies to all panels), vasodilatation (expressed in relative terms as % max; see Methods) tended to increase with vessel branch order (FA<1A<2A<3A) and with contraction duration (100<250<500<1000 ms). Across branch orders, ROV was lower for GM in old compared to young mice. Summary data are means ± SEM, n = 6 per age group.