Figure 3. Quadriceps endurance time test: the lines on the top channel represent the sustained isometric contraction at 60% value of quadriceps maximal volitional contraction (QMVC); surface electromyography (SEMG) from vastus lateralis muscle (VL-M), rectus femoris muscle (RF-M) and vastus medialis muscle (VM-M) were shown below the force line; the number below the X axis was the time (minutes: seconds).

The time to fatigue (QTf) in this figure was about 2 minutes and 20 seconds (140 seconds).