Study procedures and training protocol
quadriceps femoris muscle
The eligible patients were randomly assigned to one of the three groups: neuromuscular electrical stimulation (NMES), NMES combined with a VR distraction (NMES + VR) or control (CO) group. Randomization was generated by random.org online software [All patients underwent the standard HD care, but patients in the NMES and NMES + VR group additionally received an intradialytic NMES of the quadriceps femoris muscles (QFM) of both lower extremities using portable 4 channel stimulation STIM-PRO X9 + (Axion, Germany). The training was applied two or three times a week, but in total 60 min a week. NMES characteristics were set up on a frequency of 20 Hz, pulse width of 250 µs and a rhythm of 5 s stimulation and 2s rest. The intensity was individually adjusted in milliampere (mA) and could be determined by the patient’s subjective sensation. Three self-adhesive reusable electrodes (One: 100 × 50 mm, two: 50 × 50 mm) were placed on each of the upper leg (Fig. Approximate positioning of the electrodes for neuromuscular electrical stimulation of the quadriceps femoris muscle