Venous occlusion plethysmography vs. Doppler ultrasound in the assessment of leg blood flow kinetics during different intensities of calf exercise

Purpose
It has recently been shown that venous occlusion plethysmography (VOP) can successfully assess the rate of increase in leg blood flow (LBF) (LBF kinetics) responses during calf exercise, but there is lack of data supporting its validity.

Methods
Using Doppler ultrasound (DU) as a criterion standard technique, we tested the hypothesis that VOP would provide similar estimates of LBF kinetics responses as DU during calf plantar-flexion exercise at a range of different intensities. Ten healthy men performed repeated intermittent calf plantar-flexion contractions (3 s duty cycles, 1 s contraction/2 s relaxation) at 30, 50 and 70% maximum voluntary contraction (MVC) on different days.

Results
Resting LBF values were significantly (P < 0.05) larger for DU than VOP but the overall mean LBF responses during exercise were not different (P > 0.05) between DU and VOP (30% MVC: 330 ± 78 vs. 313 ± 92 ml/min; 50% MVC: 515 ± 145 vs. 483 ± 164 ml/min; 70% MVC: 733 ± 218 vs. 616 ± 229 ml/min). LBF kinetics analyses revealed that the end-amplitude at the highest intensity (70% MVC) was significantly higher when measured by DU compared with VOP, but all other kinetics parameters were not different between VOP and DU.

Conclusions
Given that these slight differences in amplitude observed during exercise can be explained by differences in vascular regions which the two techniques assess, our results suggest that VOP can accurately assess LBF kinetics responses during calf plantar-flexion exercise at intensities between 30 and 70% MVC.