Fig. 33. Tensions recorded in left medial rectus (upper channel, LMR) and left lateral rectus (middle channel, LLR) during unrestrained saccadic movement from primary position to 30 degree right (R, lower channel). Note initial isometric tension rise in agonist left medial rectus before eye moves appreciably, then a break in curve as eye achieves significant velocity and a postsaccadic exponential decay to a steady level. Note also that tension in the relaxing antagonist left lateral rectus increases before it assumes a new steady-state fixation level, which is several grams greater than that for primary position. (Collins CC, O'Meara D, Scott AB: J Physiol 245:359, 1975.)