We had studied the influence of physical fatigue induced by 5 min Harvard step test onto the strength of well-known visual illusions-Müller-Lyer and Ponzo. The responses of the volunteers were registered either in visual or in sensorimotor domain. The results did not show any significant changes in illusion's strength and speed of hand movements on the stimuli shafts between control and experimental group. Thus we propose that the dependence of the illusion's strength on the physical load or stress reported in some works is due to experimental design but not to the physical load by itself.