Which muscles are involved at different parts of a bicep curl's ROM?

hatrickpatrick

This might sound like an odd question, but obviously as you travel through the full ROM of a standing barbell curl, different muscles (or different sections of the muscle) are used to shift the weight. I'm just wondering, which muscles are used during the lowest part (bringing the arms up from almost straight down to having the forearms sticking out at right angles to the upper arms) as opposed to the upper part (bringing the weight from the half way up position to near shoulder height)?

The reason I ask is as follows: I'm finding that if I do partial ROM curls where I never go lower than that half way point (so starting the exercise with the weight at shoulder height, lowering to the right angle or slightly below that and returning), I can manage a MUCH heavier weight than if I go through the entire ROM. Preacher curls are far easier for me than barbell curls for this reason, and it affects my lifts in other exercises as well (to give you one example, at the moment I'm doing overhead shoulder presses with two 20KG dumbbells which I can manage easily on the exercise itself, but I find the lower part of my bicep is so weak that the only way I can get into position is if I balance the dumbbells on my knees, hammer-curl position, and then literally use my knees to "bounce" the weights upward to an angle where my bicep can then kick in and handle the rest of the movement). For the preacher curls, even though I can do them at 24kg (dumbbells, one arm at a time) I have to use my other hand to stabilize the weight at the top of the ROM before I start a set, and to catch it when the set is finished).

Now my biceps are starting to look great in my view, mass-wise there's no problem and my arms are getting pretty big, but functional strength wise this is obviously completely useless - what the hell's the point of being able to use my biceps in a strict form of exercise if I then can't use them to even pick up the weight for that exercise and get it into the starting position without assistance from my other hand?!

So basically I'm just wondering, which muscle here is the weak link? There's obviously a part of my bicep, or another muscle entirely, which isn't at the same level as whichever one is used for the shoulder-to-right-angle part of a curl's ROM. Anyone know how this works and can explain what's going on?

JJayoo

I'm finding that if I do partial ROM curls where I never go lower than that half way point (so starting the exercise with the weight at shoulder height, lowering to the right angle or slightly below that and returning), I can manage a MUCH heavier weight than if I go through the entire ROM

Most things in life are easier if you half arse them.

hatrickpatrick

JJayoo wrote: »

Most things in life are easier if you half arse them.

Haha very true, but I'm curious as to which specific muscle it is that's weaker than it should be in this scenario?

Mellor

hatrickpatrick wrote: »

Haha very true, but I'm curious as to which specific muscle it is that's weaker than it should be in this scenario?

It's the same muscle is the lower and upper portions of the lift. It's not because of a weakness either. It's just easier to lift in the upper half.
There's a couple reasons, firstly the leverage is different at different points of the movement and also because our muscles don't produce an uniform force. The force peaks somewhere in the middle of the contraction.
Stop doing partial reps.

You should using full ROM for preacher curls also, no idea why that should be easier.
And that's a pretty standard way to get into position for overhead press. If you could curl it into position, then is probably not your max press.

hatrickpatrick

Mellor wrote: »

It's the same muscle is the lower and upper portions of the lift. It's not because of a weakness either. It's just easier to lift in the upper half.
There's a couple reasons, firstly the leverage is different at different points of the movement and also because our muscles don't produce an uniform force. The force peaks somewhere in the middle of the contraction.

Ah, that makes sense I guess. I used to be the same with push-ups before I started properly training, as in I would find it unbelievably easy to do a fine set of pushups if I started from an upright, arms extended position, but I literally couldn't even almost lift myself from a flat-on-the-ground position to begin the set, if I wanted to do it that way Always wondered why that would make such a huge difference.

Stop doing partial reps.

I'm not, if I find I can only do the partial reps I put the barbell back and take a lighter one, I was merely wondering why there would be an inequality between the two halves of a curl.

You should using full ROM for preacher curls also, no idea why that should be easier.

I am, I think it's just that the preacher curl makes it impossible to cheat with one's back. A weight I find impossible for a standing curl is doable on preacher simply because my arms have no choice but to take the whole weight - I think I just have very strong lat muscles which are inclined to shoulder (no pun intended ) as much of the weight as they can. On the preacher bench, curling with bad form is practically impossible unless you consciously lean forward on it.

And that's a pretty standard way to get into position for overhead press. If you could curl it into position, then is probably not your max press.

Seriously? Thanks for that, I had no idea. TBH every time I have to use knee momentum to "bounce" my dumbbells upward before doing a set of shoulders I find it pretty demoralizing, always assumed I should be able to get them to shoulder height unassisted just using arm strength. Cheers!

Alf Veedersane

Mellor wrote: »

It's the same muscle is the lower and upper portions of the lift. It's not because of a weakness either. It's just easier to lift in the upper half.
There's a couple reasons, firstly the leverage is different at different points of the movement and also because our muscles don't produce an uniform force. The force peaks somewhere in the middle of the contraction.

Not that this point needs backing up but there's always room for a graph!

thegreatiam

Alf Veedersane wrote: »

Not that this point needs backing up but there's always room for a graph!

I love it when graphs look like what they are representing. Like a pie chart about pies.

conzy

thegreatiam wrote: »

I love it when graphs look like what they are representing. Like a pie chart about pies.

kevpants

A stretched muscle is a weak muscle. Fully stretch any muscle and it's weaker than when it is partially contracted.

No one should ever debate form when it comes to bicep curls. The only possible outcome anyone wants to experience if they are doing bicep curls is bigger biceps. If someone is showing off how much they can curl and another person is criticizing their form, both of those people are missing the point.

rubadub

Is there any sense in training partial rom using the max weight you can manage in that short rom in all exercises. I know people might do really heavy deadlifts and only shift it 1" or so in an near standing starting position. Or people using heavy chains on barbells so as the bar goes up more weight is acting on the bar. I just do not hear it much for other exercises, but is this just since its harder to do? harder as in the setup. I remember seeing bands being used for chinups, not to assist up but attached to the ground pulling down the higher you got.

With curls if you were using 1 arm the free one could assist but it is difficult to gauge the additional aid.

hatrickpatrick

kevpants wrote: »

A stretched muscle is a weak muscle. Fully stretch any muscle and it's weaker than when it is partially contracted.

No one should ever debate form when it comes to bicep curls. The only possible outcome anyone wants to experience if they are doing bicep curls is bigger biceps. If someone is showing off how much they can curl and another person is criticizing their form, both of those people are missing the point.

To be fair my biceps have been getting absolutely massive doing a mixture of full and partial curls, but what concerned me was the strength aspect since I honestly didn't realize it was normal not to be able to use the biceps unsupported to swing a dumbbell up to shoulder height for an overhead shoulder press. The fact that I've always had to use my knees to give the movement the initial momentum was making me worried that while my muscles were big, they weren't necessarily as strong as they should be - it's pretty well known that, to a certain extent, muscle mass and functional strength can often have a bit of a discrepancy between them, but I'm after both size and strength so it just spooked me a bit.

Here's a question though: Supposing you have a weight that you can comfortably do your 3 sets of 12 full contraction reps with. You then increase to the next increment (in my gym, the increments for barbells are 2.5kg, so in this case I was going from 36kg barbell curls to 38.5kg) and with that new weight, you can only do the curls from upright to just below half way down (further extension makes it impossible to bring it back up).

Is there anything at all to be said for basically sticking with the heavier one until you're strong enough to do it fully? Because what I've found over the last few weeks is that even if the initial increase in weight limits my ROM, as my muscles get used to the new weight with each consecutive workout, the maximum ROM also increases. So recently my basic thinking has been "even if the increase in weight temporarily limits ROM, after a few workouts of doing the half curls, you'll suddenly find you're able to manage the full ROM with the new, heavier weight".

It's basically the same thinking I use for rep ranges - my target is three sets of 8-12 so what I've been doing is taking a weight I can only do 8 of and working with it until I can comfortably do 12, at which point it's time to increase the weight to a new one which can only do 12 of.

These strategies are definitely working for me as far as building bigger muscles goes, I'm simply wondering if the science behind it is sound or if I could actually be doing even better with a different approach?

kevpants

I think you're overthinking the jaysus out of your curls. Strong biceps are an irrelevance, I'd struggle to think of a way they'd help you in any way shape or form. Using your bicep to shift any appreciable weight leaves you liable to tearing it clean off the bone. It's a small muscle, it's just prominent and synonymous with looking strong.

I completely neglected my biceps for years, I'm a powerlifter and biceps can't move the weights I need to move so they were put in the same group as calves. However I subsequently discovered bicep mass = healthier elbows. So I started training them and they've grown considerably. My approach is to survey my gym at the end of a session and see if there are already loaded barbells,dumbells, plates with hand grips etc lying about and I curl them.

Sometimes the weight is light and the form is ultra strict because it breaks down the muscle, sometimes the weight is heavy and I swing into it a bit or do hammer curls because it breaks down the muscle too. Sometimes I'll either have a really heavy weight (relatively speaking) or be fatigued at the end of a set so I'll do partials like you mentioned where the act of stopping the dumbell on the way down puts strain on the muscle and breaks it down.

So long as my arms are lit up and I'm done in 5-10 mins I'm happy. It's not a complicated exercise, you don't need to program for it, take your curious mind and apply it to some other element of your performance.

Alf Veedersane

You should email CT Fletcher, OP. He's something of a form guru, especially with curls.

Mellor

hatrickpatrick wrote: »

On the preacher bench, curling with bad form is practically impossible unless you consciously lean forward on it.

I get that part.
But what I don't get is how you curl lift the same weight in a normal position when you have the option of strict form or cheating.

Seriously? Thanks for that, I had no idea. TBH every time I have to use knee momentum to "bounce" my dumbbells upward before doing a set of shoulders I find it pretty demoralizing, always assumed I should be able to get them to shoulder height unassisted just using arm strength. Cheers!

If somebody could curl up their max shoulder press, I'd assume that had a weak press, not a strong curl.

Alf Veedersane wrote: »

Not that this point needs backing up but there's always room for a graph!

Thanks for that. Looked for a suitable graph but couldn't find a clear one.

rubadub wrote: »

I know people might do really heavy deadlifts and only shift it 1" or so in an near standing starting position. Or people using heavy chains on barbells so as the bar goes up more weight is acting on the bar. I just do not hear it much for other exercises, but is this just since its harder to do? harder as in the setup.

I think the difference is that in those cases, they are doing them for very clear, and thought out reasons. Specifically targeting the upper portion of the lift.

People doing partial curls aren't training for improved curl lockout, they just want to use bigger weights.