There was no significant difference in the venous diameter between the baseline and resistance exercise conditions in this study, but the venous flow velocity significantly increased. In a previous study, Ojima et al.  reported no differences in the popliteal vein or common femoral vein diameters between the at-rest condition and during electrical muscle stimulation, although peak venous flow velocities were higher during electrical muscle stimulation than at rest. Likewise, the increased venous flow volume resulted primarily from increases in the time-averaged mean flow velocity in this study using rhythmic handgrip exercise. Ishii et al.  reported a heart rate increase during the early period (10–20 s) of voluntary one-arm cranking with 35–40% maximum voluntary contraction (MVC). Victor et al.  reported that the mean arterial pressure and heart rate increased during the first minute of rhythmic handgrip at 30% MVC. However, there were no statistically significant differences in blood pressure or heart rate between the baseline and resistance exercise measurements in the present study because of the short exercise duration (20 s). Because of the differences in the exercise (including contraction and exercise times), the blood pressure and heart rate must not have been influenced in the present study. There were no adverse events attributable to the study conditions. We believe that the protocol used in the present study is safe.