Bodybuilding, as opposed to powerlifting or Olympic lifting, is about building muscle. Not only that, but each muscle must also be developed with whole-body symmetry in mind. This means it is very important to be able to focus one’s efforts on a specific muscle. For most lifters, especially those early in their bodybuilding career, the only way to focus on one muscle out of several that are contributing during an exercise, is to lighten the weight and really concentrate on “squeezing” the muscle of interest.
PROSECUTION
By lightening the weight in order to focus on a specific muscle, all you are doing is reducing the activity of all the other muscles, leaving the muscle of interest the only one really doing anything. If only one muscle is of interest during any given set, don’t do compound exercises; instead, do isolation exercises.
EVIDENCE
A study in the European Journal of Applied Physiology showed that focusing on the pecs during bench presses did indeed increase relative muscle activation of the pecs.
In the same study, focusing on the triceps also increased activation of the pecs, unless the weight was very, very light.
In a study using biceps curls, subjects were asked to focus on their biceps contracting or on the bar they were moving. In all cases, significantly higher muscle output was seen when subjects focused on the bar they were moving rather than the biceps.
VERDICT
There is no data supporting the notion that performing compound lifts with light weight in order to focus on only one muscle provides a superior stimulus compared with performing the lift in a traditional manner.
SENTENCING
When trying to bring up specific body parts, forgo trying to make one muscle do all the work during compound lifts and stick with isolation exercises. – FLEX
