>>75477812
>I can't do dumbbells as a result. I don't have this issue with curl bars or cables.
because u can stabilise the weight and crane it up with front delt and clavicular head of pec and of course by bobboing front and back your hips and torso with barbell, when u curl with db u are not able to do as much "cheating"

thing is that u're attacking long head and it is not gonna be able to flex properly because shoulder tendon is descending down from it and then turns to front so it is kinked twice, u can't work muscle when its fibers are obstructed by your own skeleton, yes it will try to flex but it will be violent and interrupted
>what am i lifting the db with then?
brachialis and brachiradialis, that pain down forearm is brachiradialis
>why does it hurt?
because u're not giving the required conditions for it to lift either - u have supinated grip and brachiradialis is tangled and twisted much like long head of biceps during curl
>and how do u propose to fix that?
by splitting the curl into two:
brachialis (brachioradialis if u're not limp-wristing which is perfectly ok):
arm as if it was on a sling across your body or if u imagined cross-drawing revolver , forearm fully pronated and u lift no further than to right angle in elbow because above that biceps tries to "help" and fuck itself up in the process

>>75478625
>by splitting the curl into two:
and long head like this:
https://www.youtube.com/watch?v=OLB82D1qi5A&pp=ygUYamF5IGN1dGxlciBjYWJsZXMgYmljZXBz
see shoulder is fully externally rotated and humerus is elevated so that origin and attachment of long head can see each other so muscle fibers are straight
>and how to emulate it with db?
lean your torso to the side (stand on sth with opposite leg it will be easier) externally rotate shoulder (like webm) and u just weigh the weight of the db on isolated muscle head belly, elbow travels back and forth and shoulder is loose

File: external shoulder rotation.gif (3.74 MB, 406x720)

3.74 MB GIF

>>75478651
>like webm

>lean your torso to the side (stand on sth with opposite leg it will be easier) externally rotate shoulder (like webm) and u just weigh the weight of the db on isolated muscle head belly, elbow travels back and forth and shoulder is loose
looks a lot like armlwrestler's setup when they push their elbow inside torso but in external shoulder rotation

>>75478625
>>75478651
>>75478661
>ok, but what about short head?
well, u can't curl for short head of biceps because u will fuck up brachialis (brachioradialis) because it will be supinated curl and it will try to "help", and u will fuck up long head also because it will be curl in internal shoulder rotation - twisted kinked muscle fibers can't properly contract obstructed by your bones
front delt will also help as much as it can by holding elbow in place
>so what is your solution
supination against resistance with supported forearm
>like rest forearm on sth and just supinate?
well no u need resistance, u need angular momentum on your wrist, tie belt on weight and wrap it around palm so that it tries to pronate your forearm by unwinding
>but do i need to rest my forearm, seems strange to work biceps without holding anything
just short head yes, otherwise u are holding the weight up with all the aforementioned muscles which will steal muscular tension from short head of biceps and u will fuck yourself up in long head elbow tendon or like in your case in brachioradialis

>>75477812
so coming back to your original question:
>Am I weak or is my body just retarded?
u're weak because u are retarded - curl is not a synonym for biceps
your anatomy is perfectly normal
>>75478625
>>75478651
>>75478661
>>75478732