Which is the better Bicep exercise?

Obviously one of the biggest and most important questions in all of physiology!

Which bicep exercise is the best? Is it the inclined bicep curl (IBC) or the preacher curl (PC)?

I'm going to try and answer this question as nuanced as I can!

First off, the IBC and PC are obviously quite similar. Both are targeting the bicep, and are relatively stable and isolated.

The main difference is the shoulder position. During an IBC, our shoulder is in extension, and when performing a PC, it's in slight flexion.

Why does this matter? Well, in order to understand why shoulder position matters, we have to look at some physiology!

1) A muscle can only shorten by approximately 50% (ish) of its resting length.

2) A muscle that is already shortened over one joint can't contract very forcefully over another.

3) The bicep is comprised of a short head that crosses the elbow and a long head that crosses both the elbow AND shoulder.

Key point:

A muscle that crosses two joints (long head of the bicep) can't produce much force when it's already shortened over one joint! So, in the PC, the long head of the bicep can't contract very forcefully, since the muscle is already shortened over the shoulder! (Oliveira et al. 2009)

Right! Does this mean that the IBC is superior to the PC?... No.

It ALWAYS depends on the context!

Let's say that you need to train your bicep, but you are dealing with some chronic shoulder pain. Then the PC might be optimal, since the force generated across the shoulder is minimal.

Or maybe you are trying to get jacked and you need to work on a specific part of the bicep!

My point is, that it does not make sense to talk about which exercise is better before we have addressed the context questions:

1) Who is training?

2) Why?

However, if you have answered these questions, then I hope that the bit of knowledge about joint angle and force production can help you choose the optimal exercises for you!

I hope you can take something away from this, and please share any thoughts/questions you might have!