Muscle Activation Is More Dependent On Load Than Form
Takeaway Points:
Tweaks to exercise form can change relative muscle activation, but the reality is that this is not as useful as most people think.
Form tweaks can sometimes limit range of motion, which makes the exercise feel harder but doesn't actually increase activation, and may in fact decrease your overall results.
At the same time, the general effect of form tweaks like this is small, and what matters a lot more to muscle activation is overall load.
Getting stronger, completing more reps, and adding weight to your lifts is more important for your long term strength and muscular growth than the exact form tweaks that you're using.
Here’s a short story from social media:
One day, I open up my Facebook to see a discussion pop up on my feed. A woman has taken a video of herself doing squats with plates under her feet. On its own, this is pretty normal - raising the heel on the foot during a squat is useful because it usually allows you a better range of motion.
This is why squat shoes are designed the way that they are: squat shoes are primarily a) very hard, to provide a solid base of support (as opposed to softer and squishier running shoes) and b) with a raised heel. This raised heel enables you to start off at a different position in terms of foot flexion, helping remove calf muscle flexibility from the equation and allowing you to go through a greater range of motion. I recommend this article for a full explanation of the forces at work. If you have particularly tight calves, the difference can be pretty big.
Now, this would be normal, except that the girl was squatting with the plates underneath the toes instead of under the heel. If you know a bit about biomechanics, it's clear that this is a bad idea. It accomplishes the exact opposite of squat shoes and limits range of motion. A greater range of motion means more strength and size in most cases, so this is counterproductive. You're limiting the amount of muscle and strength you can build, even if are targeting some muscles more than others.
I wasn’t friends with this woman, but several of my friends were having a debate in the comments. One asked her why she was squatting like that, and her reply was that someone had told her that it activates more muscle somehow. When it was pointed out that this just limits range of motion, decreasing effectiveness, she insisted that she could feel it more in whatever muscles were supposed to be getting more activation.
It’s important to realize that the feeling of activation of a muscle, while it’s a good estimate of what muscles we’re working and roughly how much, is not a good indication of exactly how much force our muscles are producing or how effective an exercise is. If it was, we could just train entirely by feel instead of using all the complicated programs that elite lifters write for themselves and others on a regular basis. While there are ways in which subjective feeling can be useful for getting a rough idea of the effectiveness of a workout or routine, exact measurements of muscle activation aren’t one of them.
For example, let’s say that you’re a bench presser whose weak point is your triceps. Your triceps will fatigue more quickly than your chest and feel the burn much sooner. You might feel like your chest “isn’t doing any work” because it doesn’t get sore or feel the burn as much, but the reality is that the pectorals are still doing most of the work - it’s just that your triceps are hogging all the attention. These two muscles are ultimately working together to achieve the goal of moving the weight, and both are important in a general sense. For the same reason, you shouldn’t judge muscle activation in the bench press based on feel, or you might mistakenly think that it’s all triceps and minimal chest!
A second, and much more important criticism, is that muscle activation is more dependent on load than form.
Let’s take a very simplified example. Say that there’s a lift which is primarily moved by two major muscles which have to work together to provide 100 units of force. Now let’s say that each muscle normally contributes equally to that total - an even 50/50 split. Now let’s imagine that there’s some form tweak that you can do that shifts that balance a little bit, making it a 55/45 split.
Now, this is a good thing for muscle 1. Muscle 1 is being more activated and producing more force. But at the same time, this comes at a cost: muscle 2 is being less activated and producing 5 fewer units of force. So, while it may be a good thing if the intent is only to target muscle 1, this isn’t really the case: both muscle 1 and muscle 2 are needed to complete the lift. If we continually train muscle 1, it will continue to get relatively stronger while the other gets relatively weaker. We would probably have to balance this out with more work for muscle 2 to make up for this later on.
In addition to that, this change isn't very big - you're still getting significant amounts of activation for both muscles. You may have added 10% to one and knocked 10% off the other, but everything is still mostly the same. The exercise still targets both muscles.
Now let’s try another approach. Say we don’t use this special form, but instead perform the lift the standard way, 50/50. Now we practice the lift, get stronger, and can handle more weight. We can put on 10% more weight, and as a result, the amount of force our muscles have to generate is 110 units instead of 100. Now, 50/50 becomes 55/55.
Do you see what happened there? Because we upped the weight, both muscles were forced to generate more force to make up the difference. This means more activation for both muscles evenly, and more strength and size built for both in the long term. This is an all around better solution.
Now, it could be argued that since the difference is small to begin with, it’s totally fine to simply stick with the variation and load up heavier instead. If you load up the 55/45 variation with an extra 10% weight, you’re sitting at 60.5 units for muscle 1 and 49.5 units for muscle 2.
But the difference between the two will become more pronounced as the load increases: at a load of 100 units, you're looking at 55/45, a difference of 10 units. At a load of 200 units, you're looking at 110/90, a difference of 20 units. As it scales, this will mean a greater overall negative for muscle 2, and you'll probably want to add in more assistance work for muscle 2 to make up for it. It's still doable, it just becomes more inconvenient over time, and more likely to lead to weak points in your physique.
If you really do care about muscle 1 a lot more than muscle 2, you’d probably still say that this tradeoff is worth it. However, this still doesn’t apply if, like in the story above, this means pointlessly sacrificing range of motion, since you’re also sacrificing the total amount of muscle recruited in the process.
This is precisely why worrying about small form tweaks (which can, at best, alter relative loading patterns) is silly. The reality is that there are many different ways to perform the same exercises which will provide comparable activation. Tiny tweaks could alter the relative activation a little bit, or we could just get stronger, toss more weight onto the lift, generate more force, and activate all the muscles involved more. By definition, this is small picture stuff.
Muscle activation is primarily driven by load. The more weight on the lift, the harder it’s going to be and the more the muscles involved are going to be activated. Don’t worry about “my hamstrings feel it more when I squat this way” when you should be worrying about putting more weight onto your squat!
I get a lot of questions about which way to tweak exercise form to get the best results. There are definitely certain, specific cases in which it’s necessary to change exercise form: if the goal is to avoid specific positions that can be potentially injurious, or to target specific weak points in your physique in order to develop strength or muscle in specific areas.
At the same time, we should never lose sight of the bigger picture: that what matters much more in the long term is proper progression of load and volume in order to drive long term growth. There's no secret magical "perfect" form that will enhance your results.
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Further Reading:
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