1. Local skeletal muscle blood flow was monitored using the microdialysis ethanol technique and 133Xe clearance during intermittent isometric contractions (5 s on/10 s off) of the thigh at 0–60% of the maximal voluntary isometric contraction force.
2. A linear increase in blood flow over a 25-fold range was detected using both l33Xe clearance and the microdialysis ethanol technique.
3. The median correlation coefficient between percentage maximal voluntary isometric contraction force and the ethanol outflow/inflow ratio, a marker of blood flow, was r = −0.98 (−0.94 to −0.99) (median and range, n = 6). The corresponding correlation coefficient for 133Xe clearance was r = 0.97 (0.92–0.98), the correlation coefficient between the ethanol outflow/inflow ratio and 133Xe clearance being r = −0.92 (−0.89 to −0.94).
4. Dialysate glucose concentration, although affected by blood flow, was not always significantly correlated with blood flow changes (r = 0.70; 0.51-0.95).
5. It may be concluded that the ethanol technique provides a valid measure of changes in local skeletal muscle blood flow. The data furthermore show that a linear increase in thigh skeletal muscle blood flow exists during the studied protocol of intermittent isometric contractions.