For best results from exercise, all of the major muscular structures should be worked – ALL OF THEM; you certainly can build large arms without working your legs – but you will build them much larger, and much quicker, if you also exercise your legs.
- Arthur Jones
The indirect effect describes the overall muscle development that seems to occur from each exercise beyond the muscles directly worked. This means that training your legs can make your arms bigger and vice versa. The indirect effect grows with larger muscles used, such as the thighs. It also seems to occur more so in muscles nearby those worked. A good example would involve squats not just affecting the thighs, but the calves as well and more so than the arms.
Squats and dead-lifts provide classic examples of the indirect effect. These exercises have long held the reputation of increasing muscle at an incredible rate. This happens throughout the entire body when progressed rapidly. The mass built in the upper body would not seem to make sense, given these serve as mainly lower body work. Programs consisting of only squats have even succeeded in stronger bench presses. This takes place without bench presses in the program. My experience has shown that progress on squats or deadlifts tend to show the general success for any trainee.
Arthur Jones described the indirect effect as a mystery. He stated that although he did not understand the process fully, he would be a fool not to act on useful information. He gave the analogy of a stone causing a ripple when tossed in a pool. The waves would radiate out from where it landed. Larger stones would have a greater effect. The ripple spreading throughout the water would eventually reach the edges of the pool.
He applied this to bodybuilding. He stated that further growth in the arms may become impossible without also stimulating the thighs. The arms need the indirect effect from the lower body. All the curls and extensions in the world would achieve nothing. He believed that widely disproportionate growth throughout the body could not occur. The body seemed to set a minimum amount of muscle for each body part. More growth elsewhere could not come about until you reached this threshold.
We now have explanations that make the indirect effect better understood. Research shows that the hormonal response to heavy, compound exercises appears much greater versus isolation exercise for smaller muscle groups. Hormones influence lean tissue growth over the entire body, so this part of the indirect effect seems clear. Heavy lifting also usually pairs up with large amounts of eating, such as with GOMAD. This leads to overall strength and size. Adding bodyweight increases total muscle mass everywhere even in untrained subjects.
The closeness as a factor may occur due to actual tension taking place. Tension is the squeezing you feel as a muscle contracts. Although many view the squats as a thigh exercise, plantarflexion does occur at the ankle. This means that the calves contribute tension to the exercise. So although many think compound exercises seem to focus on the largest muscles alone, the smaller muscles also add tension.
Disproportionate growth is certainly possible since tension represents the main stimulus for growth. We have all seen the bodybuilder with huge arms and comparative chicken legs. Yet, think carefully. Try to imagine someone looking strong in only a single body part. This person will still have some size everywhere. The bodybuilder’s so-called chicken legs still had some girth. This likely also happens due to hormones. Perhaps some other unknown regulation by the body also takes place.
What information does the indirect effect give us?
- Never skimp on leg training.
Your overall progress will suffer. Many trainees lift heavy to grow their upper body. They then consider wimpy long distance running sufficient for the lower body. Beyond the obvious shortcomings of such an approach, ignoring the lower body would reduce the growth potential of the upper body too.
- Work the largest muscle groups first.
For full body workouts, this usually meant beginning with the thighs and hips. Afterward, you would move on to the upper back. You would then proceed with the chest. From here, you would hit smaller muscles according to size. You do not have to practice it this way. Just use an exercise order that does not harm the results of your squat, push, and pull. In some cases, this may still require you to squat or deadlift first.
- Train every muscle group.
Each muscle worked has the power to influence the growth of other muscles. Compound movements require greater assistance from the stabilizers to produce tension. This tension throughout the body stimulates a lot of muscle at once. This furthers the benefits from the indirect effect. It supports focusing on compound, free weight exercises. I would argue these are all you need for resistance training. These work best for other important reasons as well, especially safety.
Some modern research shows that all growth may occur locally. The indirect effect still remains somewhat mysterious or perhaps even untrue. If it turns out overblown or false, following an approach dictated by the indirect effect would still lead to the best results. Training every muscle group, never ignoring leg training, and using exercises that address lots of muscle would work best even if the indirect effect turns out to be a myth.