The Indirect Effect

In Chapter Four of Nautilus Training Principles: Bulletin Number One titled, Indirect Effect, Nautilus inventor Arthur Jones wrote,

“Throw a stone into a pool of water, and it will make a splash—and a wave will run to the far end of the pool; the larger the stone, the larger the splash—and the larger the wave. A very similar effect results from any form of exercise—I have named this “indirect effect”. When one muscle grows in response to exercise, the entire muscular structure of the body grows to a lesser degree—even muscles that are not being exercised at all; and the larger the muscle that is growing—or the greater the degree of growth—the greater this indirect effect will be.”

Jones believed performing exercises like barbell squats involving several large muscle groups would “indirectly” stimulate growth elsewhere in the body, although to a lesser degree. He thought you could not produce significant increases in muscular strength and size in some body areas without growth in others because there was a “…limit to the degree of such disproportionate development that the body will permit…” While Jones admitted the cause was unknown at the time it was eventually assumed to be the result of increases in anabolic hormones stimulated by intense exercise. It turns out this is not the case, however, and “…acute post-exercise systemic hormonal rises are not related to or in any way indicative of RT-mediated gains in muscle mass or strength.”(1, 2, 3)

It is possible to increase a muscle’s strength indirectly by performing exercise for it’s contralateral match,(4, 5, 6) however the effect is muscle-specific rather than general and primarily due to neural adaptations and not hypertrophy.(7) This contralateral effect would not explain the general indirect effect Jones wrote about, although other neural factors might be involved.

Indirect Effect

The more likely answer is a much simpler one; that the effect being observed is not indirect at all, but the result of those other muscles also being worked at least moderately hard during the exercise.

Although the barbell squat primarily targets the muscles of the hips and thighs, as the weight used becomes heavier the muscles of the arms and back must also work hard enough to control the bar to benefit from the exercise. This effect can also be seen in exercises like the barbell row and standing press. The barbell row and standing press primarily target the muscles of the upper body, but as the weights used become heavier the muscles of the trunk, hips, and thighs must work harder to maintain proper body positioning and would also be affected by the exercise.

When a leg press machine, compound row machine, or shoulder press machine are used instead the same effect is not seen because the bracing these machines provide tends to minimize the involvement of those other muscle groups. No demanding muscular work, no stimulus for growth.

Just because these stabilizing muscles are involved in free weight exercises does not mean they are worked effectively by them, though. How intensely a muscle is worked determines how effectively it is stimulated to grow, and these muscles are not being worked as effectively as possible in stabilizing roles. This is why it is important for your workouts to include one or two exercises for all muscle groups. While a small number of compound exercises can effectively target all the big muscle groups, if you want overall well-balanced and proportional muscular development you need to work everything and not depend on the indirect effect for optimal development of muscle groups like your abs, calves, forearms, and neck.

References:

  1. Morton, R. W., Oikawa, S. Y., Wavell, C. G., Mazara, N., Mcglory, C., Quadrilatero, J., . . . Phillips, S. M. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. Journal of Applied Physiology J Appl Physiol. doi:10.1152/japplphysiol.00154.2016
  2. West DW, Burd NA, Tang JE, Moore DR, Staples AW, Holwerda AM, Baker SK, and Phillips SM. Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. J Appl Physiol (1985) 108: 60-67, 2010.
  3. West DW, Kujbida GW, Moore DR, Atherton P, Burd NA, Padzik JP, De Lisio M, Tang JE, Parise G, Rennie MJ, Baker SK, and Phillips SM. Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men. J Physiol 587: 5239-5247, 2009.
  4. Zhou S (2000) Chronic neural adaptations to unilateral exercise: mechanisms of cross education. Exerc Sport Sci Rev 28: 177–184 [PubMed]
  5. Munn J, Herbert RD, Gandevia SC (2004) Contralateral effects of unilateral resistance training: a meta-analysis. J Appl Physiol 96: 1861–1866 [PubMed]
  6. Carroll TJ, Herbert RD, Munn J, Lee M, Gandevia SC (2006) Contralateral effects of unilateral strength training: evidence and possible mechanisms. J Appl Physiol 101: 1514–1522 [PubMed]
  7. Lee M, Carroll TJ (2007) Cross education: possible mechanisms for the contralateral effects of unilateral resistance training. Sports Med 37: 1–14

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  • Ben Oct 15, 2016 @ 19:16

    Mr. Baye,

    I’ve only recently begun to read through the articles posted on this site and I have to admit it’s refreshing to see someone use empirical data and evidence to support their position, especially in the now often speculative world of personal training and exercise science. I stumbled upon your website while attempting to do research on methods such as ballistic isometrics, plyo, and all of the other usual suspects people buy into when it comes to attempts to increase speed/agility/explosiveness. I currently go to a HIIT gym called Fit36 in Denver which follows push/pull type principles and am certainly going to start going away from the idea of explosive movements in exchange for slowing the reps down (particularly the negative) and also going heavier with regard to weight. Big fan of isometrics as well, our strength and conditioning coach in college emphasized them heavily during the off season and the results were significant. I’m curious to hear your thoughts on recovery post-workout and how important, if at all, it is to stretch/cool down or use a foam roller after a hard HIIT workout. I’m guessing you’ve addressed this at some point already and I just haven’t gotten to the article yet. Looking forward to hearing back from you!

    • Drew Baye Jul 28, 2017 @ 13:55

      Studies are mixed on the benefits of post-workout stretching and foam rolling doesn’t appear to do much other than reduce delayed-onset muscle soreness.

  • Roberto Casanova Oct 19, 2016 @ 17:43

    Drew,
    Thanks for offering your view on why the indirect effect happens. If I’m understanding correctly, it seems that, for some movements at least, barbells/dumbells may be more effective in terms of using as much of the muscles as possible. I think (but could be wrong) this is also true of some bodyweight exercises, such as pushups, where the legs, abs, and even lats are engaged especially as you get closer to failure. I have noticed that my body feels somewhat different (not much though) after going through a barbell/dumbell workout as opposed to machines. Unfortunately, at my age (55) barbell squats, bench presses, and overhead presses tend to aggravate my wrists and shoulders, so I do them with dumbells. Deadlifts I do with a Nuatilus Plate Loaded machine. Squats I do with a combo squat/hack squat machine (plate loaded) which doesn’t require me to reach back with my hands behind my head to hold a barbell. Presses and bent over dumbell rows are more wrist/shoulder friendly for me as well. Would you say that more stabilization is required with dumbells due to them being independent of each other? If so, would you also say that this would result in more of an “indirect effect”.

    • Drew Baye Jul 28, 2017 @ 13:45

      Stabilization during free weight and bodyweight exercises requires involves more muscles in an exercise, but this does not mean they are being efficiently loaded or effectively stimulated to get bigger and stronger. The degree of indirect effect would depend on the efficiency of muscular loading, which would vary between exercises.

  • Bradley Dec 7, 2016 @ 19:35

    Hi Drew,
    I totally agree with what you say here and can relate well to it based on my experiences as a teenager starting out lifting weights. I was always told that I should practice the big lifts for overall development and reading AJ’s Nautilus articles made me even more inclined to practice this way of training. It eventually led to me being quite out of proportion ( in the bodybuilders aesthetic sense) with overly developed gluteus from all the squats and deadlifts, and overdeveloped front deltoids from all the barbell bench pressing and shoulder pressing etc.
    it took me some years to realise that this indirect effect is actually not entirely true and now knowing that the hormonal responses are relatively poor even after performing compound movements just makes it more clear how important it is to directly isolate a muscle as much as possible if your goal is to enhance its development as quickly as possible.
    One other thing I have noticed over the twelve years I have been training is the number of athletes and sports people, such as cyclists and runners who have significantly disproportionate leg development due to the particular demands of the sport, yet in complete contrast they often have upper bodies that look like someone who have never workout out in their life. This observation, along with other like it, although anecdotal, really sealed the deal for me.
    thanks Drew and keep up the good work

    • Drew Baye Jan 9, 2017 @ 14:34

      Hey Bradley,

      You’re welcome, and thanks for bringing up cyclists. I’ve noticed the same thing, and if the indirect effect did work the way some people believe more cyclists might have better upper body development, although selection bias (better genetics for lower body strength) probably also plays a significant role in this.