Fig. 4.

Hemodynamics in the femoral vein measured in PVV (A) and intensity of NMES (mA) required (B), at muscle contraction (ML I) and after an increase of six NMES levels from muscle contraction (ML II), for stimulation a frequency of 1 Hz, 36 Hz, and 66 Hz. Both 36 Hz and 66 Hz required significantly less intensity to reach both ML I and ML II, as compared to 1 Hz (B). p-values calculated with Wilcoxon signed rank test, significant values are bold. a: p < 0.01 compared to the same frequency at ML II, *outlier, 144 cm/s for ML II 36 Hz, and 146.5 cm/s for ML II 66 Hz. Q-NMES neuromuscular electrical stimulation of the quadriceps muscle, PVV peak venous velocity, mA milliampere, ML measurement level