This is an excerpt from Strong & Sculpted by Brad Schoenfeld.
Most lifters have a limited number of favorite exercises that are staples in their routines. That's human nature. However, although it's OK to have your old standbys, they shouldn't be performed at the exclusion of other movements. In fact, varying exercises through a multiplanar, multiangled approach is essential to fully develop complete symmetry both within and between muscles.
The importance of variety is apparent from basic functional anatomy (see figures 2.2 and 2.3 for full-body muscle illustrations). Muscles often have diverse attachments to optimize leverage for varying movement patterns. For example, the deltoids are subdivided into three distinct heads that carry out separate functions: the anterior head flexes the shoulder (raises the arm forward); the middle head abducts the shoulder (raises the arm to the side); and the posterior head horizontally extends the shoulder (moves the arm away from the midline of the body from a position where it's parallel to the floor). These unique functions can be trained by performing a front raise, lateral raise, and bent fly. In this way, you target each respective deltoid head so that all fibers are maximally stimulated.
Full-body female anatomy (anterior view).
Full-body female anatomy (posterior view).
OK, so perhaps this isn't news to you. What you might not know, however, is that it's actually possible to target portions of the same muscle fiber! Contrary to what was once thought, fibers don't necessarily span the entire length of the muscle from origin to insertion. Rather, they are often segmented into neuromuscular compartments, each of which is activated by its own nerve branch. In fact, a majority of the large muscles in the body are compartmentalized in this fashion. This has wide-ranging implications for body sculpting. For example, a recent study from my lab found that the leg curl (a knee-dominant exercise) activated the lower aspect of the hamstrings to a much greater extent than the stiff-leg deadlift (a hip-dominant exercise) (Schoenfeld, Contreras, et al., 2015). The findings suggest that the partitioning of muscles provides a mechanism for their greater regional-specific activation.
Importantly, an emerging body of research indicates that the selective activation of different areas of a muscle is consistent with where growth occurs in that muscle (Wakahara et al., 2012, 2013). Translation: Activating aspects of a given muscle can influence the extent of its development. A key takeaway here is that optimal body-sculpting results can be achieved only by working all aspects of all the major muscles, and this can be achieved only by performing a variety of exercises.
With respect to exercise selection, the concept of variety needs to be expanded beyond simply performing an array of exercises; you also need to take into account how these movements interact with each other. Basic kinesiology dictates that certain exercises are complementary, working synergistically to produce optimal results. Factors such as the angle of pull, plane of movement, length - tension relationship, and number of joints involved influence how effectively you work a given muscle. Unfortunately, most lifters do not fully comprehend these complexities and continue to haphazardly string together a series of exercises without regard to how they mesh.
The good news is that you don't have to be an exercise physiologist to create a cohesive routine; the Strong and Sculpted plan takes all the guesswork out of exercise selection. You won't have to worry about deciding which movements mesh best; I've done all the legwork for you. Exercises for each muscle group are categorized based on applied kinesiological principles. Simply choose from the categories as directed, and you're guaranteed to effectively target the areas of the muscle complex you are working on that day. The result will be complete development of your physique over the course of the training program.
Learn more about Strong & Sculpted.