Table 1.

Measurements of vastus lateralis and biceps femoris muscles.

Position of measurement

Vastus lateralis: Measurements on the VL were performed in the supine position at 30° knee flexion, where 0° represents the extended joint.

Biceps femoris: Measurements on the BF were performed in the prone position at 5° knee flexion.

Procedure

1. Place the muscle to be measured in a relaxed, predefined position and evoke muscle contraction by applying a brief electrical stimulus.

2. Prepare a pair of self-adhesive stimulation Pals electrodes (50 mm diameter) (AxelGaard, Fallbrook, CA, USA).

3. Measure the muscle in a bipolar way in that the negative electrode (cathode) is installed 5 cm distal and the positive electrode (anode) 5 cm proximal to the measurement point.

4. Select the measurement point where the belly muscle is largest while ensuring that the selected place is between the two electrodes. Start the experimental measurements (with palpation and re-installation of the electrodes and sensors if needed). Because each muscle has its own specific anatomical structure, some adjustments may be needed regarding the locations of the measuring equipment.

a. Vastus lateralis: Set the sensor perpendicular to the skin overlying the muscle belly at 30% of the femur length above the patella on the lateral side.

b. Biceps femoris: Set the sensor perpendicular to the skin overlying the muscle belly of the BF at the midpoint of the line between the fibular head and the ischial tuberosity.

VL = vastus lateralis; BF = biceps femoris