So I keep seeing these bodybuilder vs mma fighter videos on youtube...

Situation depends really. If you think about it most fights are started with haymakers/cheap shots. Gracie combatives teach defense against those specific scenarios.

What's the science behind this beach muscles, strength muscles, fighting muscles shit. I hear mma fighters don't train their pecs because it doesn't help with punching power and just adds to their weight (see mcgregor and friends)

I just carry a gun and try to be as polite as I can be so I dont have to use it... but to each there own.. then again I am 36 and not some dumb punk kid who thinks he is going to win every battle anymore.

Or is that just an excuse for his piss poor pec inserts

Punching is more a whip motion of tendons and ligaments than a push using pecs. Your pecs mostly just stabilize your arm when punching.

It comes down to more momentum (mass times velocity) than force (mass times acceleration)

Punch power comes from the whip motion, created by your legs and hips. Leg strength more important than arms in throwing more damaging punches.

jesus that hgh gut

If I build a icf 5x5 + cardio bod will I be able to throw a powerful punch?

its a street fight nigga, just carry around trusty old pipebomb

It's a thing. A fighter isnt gonna waste his time doing curls or tricep kick backs to sculpt his muscles. Nor is he gonna waste the time hitting his chest with 3 different exercises that day for a pump. He's gonna focus on speed and power. Which are compound plyo's like clap pull ups and push ups and do more of an Olympic power lifting routine for strength.

So theres your difference shit lord. You have to be retarded.

it depends. i only do striking in the form of boxing so i cant talk about grappling, but striking gets you a decent body.

also matters how you train, your inherent physical proportions, your style of striking, your weight class and what level of competition you want to fight at, if any.

obviously if you train cardio a lot you're going to get lanky, but im talking more about how you train on the bag, speed vs accuracy vs power. if you train for speed you'll end up lanky. the opposite is true for power.
that is affected by how you fight. if you outbox then you're better off training for speed and accuracy, while if you're built like a slugger then power is more important.
that in turn is influenced by your body proportions. if you're tall and lanky then you'll find you perform better as an outboxer, and your training will be affected in turn. same goes for the others. i.e. if you have good power but shit speed/accuracy, you'll find you fight better as a slugger and subsequently train to be a better slugger.

weight class also affects how you train. if you in lightweight you should train for speed since knockouts are rare. the opposite is true in heavyweight.

you also need to take into account level of competition. amateurs require speed over power, since you are there to score points, while professionals do better with more power and endurance vs speed, since they need to go the distance or get a knockout.

its quite complicated, but as a rule of thumb, fight the way you fight, not the way you want to, and train to get better at fighting the way you fight.
if you realize you fight better through speed but dont want to end up lanky, then maybe bodybuilding is a better way to go.

whatever you do DONT do both at the same time. lifitng fucks with your whole body coordination and you will end up tense in fights and get fucked over easily. that or you create a muscle imbalance and end up hurting yourself.

you're a retard.
where does the force come from? oh yeah, that's right, your muscles moving your limbs.
and its force, not velocity, because if it was velocity they'd be standing still. in which case its still force. learn basic physics.

no. punching is a whole body exercise. training specific muscle groups dont help. that being said, once you have the technique down, you'll find that you have certain muscle groups too weak to stabilise your body, causing a decrease in your punching strength. only then can you fix it through exercises that target that specific group.
for me that's abdominals, which is why i do a lot of dynamic abdominal exercises like crunches etc.
i alternate between abdominals and legs, since they're usually the two limiting factors of my power, not arms.

that's kinda right.

your pecs arent really actively involved in any punches (even in hooks they ave a lesser effect than core and hip rotation).

that being said, MT clinching relies on pec muscles a lot, as does the front guard in boxing. i guess its less important in MMA since you cant block punches well with those small gloves.