Figure 4 - Assessment of voluntary rhythmic muscle contraction-induced exercising blood flow variability measured by Doppler ultrasound

Relationship between net-femoral arterial blood flow (FBF) and target workload during dynamic knee extensor exercise. The relationship between FBF and target workload was positive and linear at 30 cpm (r = 0.997, P < 0.01, n = 4) and 60 cpm (r = 0.999, P < 0.05, n = 3), respectively. The value of FBF for one subject was the average value of 60 samplings at each session. Furthermore, the target workload value in each individual subject was determined by averaging values of 60 samplings of the achieved workloads at each session. Both FBF and target workload were obtained from average values of all 9 subjects. Regression equations are indicated as follows: FBF (l/min) = 1.71 + 0.083 × target workload at 30 cpm (solid line): FBF (l/min) = 1.52 + 0.098 × target workload at 60 cpm (short dotted line). These data are in close agreement with the findings of Rådegran [6]: FBF (l/min) = 1.317 + 0.084 × target workload at 60 cpm, long dotted line. The difference in absolute FBF was approximately 0.5 l/min between the present FBF data and previous reports at 60 cpm by Rådegran [6]. This difference may be due to the subjects' characteristics, such as muscle strength variations and that they worked at different percentages of the maximum voluntary knee contraction force. However, the slope of the regression line in the present study is similar to previous findings. cpm, contractions per minute. Data are expressed as means  standard error. Figure adapted from Osada and Rådegran [32], reproduced with permission from John Wiley & Sons Ltd.