Fig. 4. Comparison of muscle activities between groups. ST-plank: the plank position on stable ground, US-plank: the plank position on unstable ground, SL-plank: the plank position using a suspension device, REO: right external oblique muscle, LEO: left external oblique muscle, RRA: right rectus abdominal muscle, LRA: left rectus abdominal muscle, RES: right erector spinal muscle, LES: left erector spinal muscle, MVIC: maximum voluntary isometric contraction (*p<0.05).
