Voluntary increase in latissimus dorsi muscle activity during the lat pull-down following expert instruction

It has been observed anecdotally that while performing the multijoint lat pull-down exercise, novice strength trainers often rely on the elbow flexors to complete the movement rather than fully utilizing the relevant back muscles such as the latissimus dorsi (LD) and teres major (TM). The primary aim of the study was to determine whether specific technique instruction could result in a voluntary increase in LD and TM electromyographic (EMG) activity with a concurrent decrease in the activity of the biceps brachii (BB) during the front wide-grip lat pull-down exercise. Eight women with little or no background in strength training were asked to perform lat pull-down exercise with only basic instruction, performing 2 sets of 3 repetitions at 30% max. After a brief rest, subjects then performed the same 2 sets of 3 repetitions following verbal technique instruction on how to emphasize the latissimus while de-emphasizing the biceps. EMG activity of the LD, TM, and BB were recorded, converted to root mean square, and normalized to the maximum isometric EMG (NrmsEMG). A significant increase was seen in Nrms EMG in the LD (p = 0.005) from the average of preinstruction NrmsEMG to the average of postinstruction NrmsEMG. No significant differences were observed between pre- and postinstruction muscle activity in the BB or TM. The results show that untrained individuals can voluntarily increase the activity of a specified muscle group during the performance of a multijoint resistance exercise, but the increase probably does not represent "isolation" of the muscle group through voluntary reduction of activity in complementary agonist muscles.