The mind-muscle connection is a valuable tool that bodybuilders can use to enhance muscle growth. Some skeptics feel that this concept is not real science and is just bro-science talk. Yet the mind-muscle connection is real and there is solid evidence of its existence and its benefits.
Researchers from the University of South Carolina Upstate had weight-trained football players perform 3 sets of the bench press with their 50% RM (a weight they could do for more than 20 reps) and 3 sets with their 80% RM (a weight they could do for about 7–8 reps) while they measured the muscle activity of their pecs, triceps, and front delts. In the first set they were given no instructions. In the second set they were told to use just their chest muscles. And in the third set they were told to use only their triceps muscles.
When the subjects used the light weight (50% RM) and were instructed to use just their chest, the muscle activity of the pecs increased by 22% compared to when they had no instruction. And when they were told to use only their triceps while lifting the light weight, their triceps muscle activity increased by 26%. During the heavier lift (80% RM) the increase in muscle activity of the focused muscles were not as significant.
Focusing on a specific muscle during exercises such as the bench press can increase the use of that muscle, but this may be more effective with lighter weight.
When lifting with heavier weights (sets where your rep range is 8 reps or less) focus on lifting the most weight. But with lighter weight, sets of reps of 10 or more, focus on the target muscle group as this can increase that muscle’s activity during the lift. And more muscle activity can lead to greater muscle growth in the long run.
Reference: Snyder, B. J., J Strength Cond Res., 2012 Sep, 26(9):2394-400.