Biceps & Brachialis activation.. question ??

[KhoraskGTR]

Bit confused about how to activate the biceps after reading exRx.nets comments on Bicep & Brachialis activation during common 'bi' exercises.

It says, "During a dynamic elbow flexion, the biceps is more readily activated than the brachialis. Alternatively, the brachialis becomes more readily activated during isometric elbow flexion."

to me that makes sense.. but when looking at the exercises where the target muscle is the Biceps and where the target is the Brachialis, is where I get confused.

eg. A barbell curl targets the Bicep with the Brachialis assisting. Conversely a Preacher curl with barbell targets the Brachialis with the Bicep assisting.

If you do the barbell curl with strict form how is this movement dynamic (and hence, "brachialis becomes more readily activated") ??

Is it just because the elbow can travel 'slightly' during the movement mo matter how hard you try to keep it 'tucked in and stationary' ??

[Bostongeorge617]

I have never heard that preacher curls target the brachialis with bicep assisting. I have always read it the other way around. The simplest way to look at it is if your hand is pronated during a curling movement, you are primarily activating brachialis and brachioradialis with bicep assisting. If it is suppinated, bicep brachii is the primary muscle.

So hammer curls, reverse barbell curls, rope cable curls, are examples of brachialis movements.

[-Lucifer]

So hammer curls, reverse barbell curls, rope cable curls, are examples of brachialis movements.

Add to that: close grip preacher curls.

[ocn2000]

You cant completely eliminate the bicep in a reverse curl, but, if you perform the curl slowly and pause at the top (isometric), the bicep does less work and the brachialis does more work.

It's best to do them slow and strict with lighter weight, even on a preacher bench in order to maximize brachialis development.

[KhoraskGTR]

I have never heard that preacher curls target the brachialis with bicep assisting. I have always read it the other way around.

Well that's where some of my confusion starts.. I (and alot of people on here) get their info from exrx.net & http://www.exrx.net/WeightExercises/...acherCurl.html says its the other way around ?

The simplest way to look at it is if your hand is pronated during a curling movement, you are primarily activating brachialis and brachioradialis with bicep assisting.

Similar to above, exrx.net explains the brachioradialis is primary activated with the brachialis assisting

Anyway.. not trying to over complicate the discussion.. my original question was really (assuming exrx.net is correct) how are movements like a standing barbell curl and a preacher curl considered different ? i.e one involves dynamic elbow flexion, the other isometric ?? they seem the same to me.. and you obviously

[celc5]

my original question was really (assuming exrx.net is correct) how are movements like a standing barbell curl and a preacher curl considered different ? i.e one involves dynamic elbow flexion, the other isometric ?? they seem the same to me.. and you obviously

Standing BB curl vs. Preacher curl shouldn't make a difference in terms of brachialis and brachioradialis. They are secondary muscles in both movements.

The difference lies in the "slack" vs. "tension" in the biceps. An easier example is with incline curls where the biceps origin (above the shoulder) is pulled taught throughout the movement, hence a bit more stretch. With preacher curls, the biceps origin has more slack without the stretch, which for some allows a stronger contraction (similar to hero cable curls).

Standing BB curls are somewhere in between incline curls and preacher curls in terms of "slack vs. tension." Incline, standing, or preacher positions should not have a drastic effect on the secondary muscles because they do not cross the shoulder.

In terms of the preacher curl question, I suppose it's possible that narrow vs. wide grip may slightly change the work required by the brachialis. In my opinion it would probably be negligible IF we could even prove that changing grip did somehow change brachialis tension.