The effect of low and high packs of various weights on trunk inclination was studied. The loads used in this study were O, 20, 40, 60, and 80 pounds. Still pictures were taken while the subjects were standing and while they were walking on horizontal, downgrado, and upgrade planes on a motor-driven treadmill 0 The speed of the treadmillp for walking, was 2.8 mph. During walking, two body positions were photographed:​ when the subject's center of gravity was at the lowest level, and when the subject's center of gravity was at the highest level. A total of 600 pictures of eight subjects was analyzed to determine degrees of trunk inclination. Although there was a definite trend showing that the low pack caused greater trunk inclination, the difference between the mean angles of trunk inclination caused by the high and low packs was not statistically significant. The latter probably depended on the small number of subjects used in this study. A lesser degree of trunk inclination with a high pack may be one of the reasons why most men prefer a high pack to a low one.