Then you will fail… at least in bodybuilding. You’ll overemphasize muscles located medially, not training all those leading to a well-proportioned, intricate physique.
This is not to say that compound exercises have no value. Especially with medium grips & stances, they address lots of muscle. They are easy on the joints.
Pressing hits the lateral & medial heads of the triceps, defining that horseshoe shape.
Pulling hits the brachialis toward bigger & fuller arms.
Squatting hits each vasti head (medialis, lateralis & intermedius) for thigh size & curves.
This is beyond the large muscles they target like the chest & front delts, lats & traps, and glutes.
However, multi-joint exercises do not adequately train multi-joint muscles! Ignoring them means leaving a lot of muscle “on the table.”
These include the 3 largest heads of the hamstrings (semitendinosus, semimembranosus & biceps femoris long head) for a balanced lower body.
It means not hitting both heads of the gastrocnemius for diamond-shaped calves.
The rectus femoris of the quads won’t show impressive front thigh detail.
The arms will highlight no biceps peak and be without the frame provided by the long head of the triceps.
Other muscles like the sartorius for thigh separation will suck too.
The distinction here is really between multi-joint and single-joint. All exercises are compound in the sense that more than several muscles come into play. A pull-over is pure shoulder extension, though inviting at least the outer chest & long triceps head.
Why Does This Matter?
If a student of bodybuilding, you would find this approach odd. No champions have trained this way.
Yet many trainees with bodybuilding goals, but a lack of knowledge, will pursue minimalist programs based on squats, dead-lifts & bench presses alone.
They don’t understand what they exclude. They may assume, for example, that arm extension on bench presses is the same as on skull crushers.
Perhaps they add vertical movements like overhead presses & pull-ups. Dips & rows could be thrown into the mix. This variety makes no difference whatsoever.
These routines bring other flaws like high frequency. They often involve unnecessary, explosive Olympic lifts. They may ignore general health through aerobic fitness.
Reg Park, the great classic bodybuilder that inspired many of these routines, trained nothing like how they are practiced today. He applied 5×5 to a myriad of exercises, both multi & single-joint, alongside plenty of traditional 8-12 rep work.
Multi-Joint Versus Single-Joint Muscles
Multi-joint muscles stay about the same length on concurrent movements, not working hard because they don’t generate power like the single-joint muscles do.
They instead maintain tension to facilitate smooth movement, transferring force between joints along the kinetic chain.
Imagine pulling on a rope without an anchor. The other end keeps moving toward you. How could much tension develop?
This dampening effect is tremendous. For example, compared to leg presses even with heavy loads, the rectus femoris had similar activation on a leg extension with only 20% 1RM! This phenomena occurs on pressing, pulling & squatting as well.
Research on multi vs. single-joint exercises may only measure bodypart thickness, not where the development came from among other issues. For this study on lat pull-downs vs. bicep curls, no distinction is made between the 2 elbow flexors within the arm.
An underhand, close grip on pull-ups doesn’t help either, as no amount of uninhibited elbow flexion matters alongside shoulder extension.
Should I Still Include Compounds?
Of course! These usually work the largest muscles best.
Beyond the risks of using heavy weights, overloading midpoints is safest. Isolation can stress the joints through shearing forces. It may involve severe ascending or descending strength curves, which also harm performance when near active & passive insufficiencies.
A dumbbell fly, with slightly bent elbows, isolates through horizontal adduction for the chest & front delts, overloading the stretched position.
A bench press has a parabolic strength curve better suited for most trainees unless trying to work the coracobrachialis.
Compound-Only Routines?
A bodybuilder should leverage both compound & isolation exercises to train all the vital muscles.
They may ignore some to achieve the right effect, like avoiding direct work for the obliques & upper traps to foster the illusion of upper body width.
A bodybuilder should be safe. Leg presses or hip thrusts may work better for some while still targeting the glutes as squats do. The classic exercises work great but aren’t sacred, even if more practical for home training.
Bodybuilders need exercises like bench presses & rows. They also include arm curls, arm extensions, leg curls, stiff-legged dead-lifts or good mornings, leg extensions or sissy squats, and other exercises to be well-rounded.
They ask themselves, is my development sufficient? Gripping that already takes place will train the flexors of the forearm, but perhaps you need a wrist curl too. You determine this based on self-evaluation.
Unfortunately, self-deception may emerge here.
We say to ourselves that what ought to be true, most certainly is. We tell ourselves that the biceps worked hard on those rows. Everything is so elegant now!
Be honest about what you desire and how to reach it best. Do you want to perform compound exercises only? Okay… just admit you aren’t bodybuilding too!