FOREARM BLOOD-FLOW BY DOPPLER ULTRASOUND DURING REST AND EXERCISE - TESTS OF DAY-TO-DAY REPEATABILITY

The between-day repeatability of simultaneous measures of brachial art ery diameter (D) (echo Doppler) and mean blood velocity (MBV) (pulsed Doppler) was tested during rest and exercise. On 3 separate days, six volunteers performed one trial of 1-min rest followed by a step increa se in dynamic handgrip exercise for 4 min which required the lifting a nd lowering of a 4.4-kg weight (similar to 8-12% MVC) in a 1s/2s (work /rest) cadence. Measures for MBV and D were collected continuously on a beat-by-beat basis during the transition from rest to end exercise. The mean rest values over one min, and single data points at 30, 60, 1 20, and 240 s of exercise were extracted from the time series data. At all exercise time points, MBV was greater than rest (P < 0.05), but t hese levels were not different across test days. Arterial D at all exe rcise time points ranged from 3.8 +/- 0.1 mm to 4.1 +/- 0.1 mm (mean /- SEM) and did not differ from rest (3.9 +/- 0.1 mm) (P > 0.05), nor did D differ between days. The mean between-day coefficient of variati on for D was 4.08 +/- 0.7% at rest and ranged from 2.90 +/- 0.4% to 3. 96 +/- 0.5% during exercise. The coefficient of variation for MBV was 13.2 +/- 2.6% at rest and reached 20.2 +/- 3.1% during the final min o f exercise; the exercise variability was reduced to 14.9 +/- 2.4% by a veraging MBV over 3 s (the duration of a contraction/relaxation duty c ycle) (P < 0.05) with no further advantage of averaging over ten 60-s sample periods. The data indicate that, for the six subjects tested, D oppler ultrasound measures of arterial MBV and diameter during both re st and exercise were reproducible across different test days and can b e used as a reliable, noninvasive means of testing hypotheses pertaini ng to blood flow control.