The effects of load placement on the EMG activity of the low back muscles during load carrying by men and women.

Abstract

An electromyographic (EMG) study of the lumbar paraspinal muscles during load carrying was undertaken in a group of 24 healthy subjects, 12 male and 12 female. Two different magnitude loads (10% and 20% of the subject's body weight) and four different carrying positions were compared with walking without an external load. Results indicated changes in back muscle activity showing a significant interaction between load magnitude and carrying position. Compared to walking without an external load, lumbar paraspinal EMG activity showed slight decreases when loads were carried in a backpack position or in the hand ipsilateral to the muscle. EMG activity contralateral to the hand carrying the load was significantly increased. Significant increases occurred when loads were carried anterior to the chest with the arms and a significant difference was found between male and female subjects for this carrying position. These findings have implications for the selection of carrying methods.