I am 13 and i want to build muscle
the workers at my gym say if i can do 30 reps of any of the machines at any weight i am alright is this true?
if not what machines should i use that will not stunt my growth?
is there any machine i should never use because it will stun my growth?
i am a fit kid and very unvulnerable to injury
all my friends workout and it doesnt seem to stunt their growth
how do heavy weights stunt your growth anyway?

A: 30 reps and your alright to train? What a load of bollocks.
Ok, your still fairly young but that's not to say you can't do some form of weight training, you just need to select your exercises sensibly.
I was going to recommend a personal trainer, but going off what you stated in your question, it doesn't seem to me like they know a whole lot.

For now, commence your training by sticking to basic movements, you know, familiarizing yourself with the various machines...

Target: Upper Chest

Forget boring old inclines! Do this instead...

...Smith Machine Presses To The NECK!

Lie flat on a bench with the Smith Machine bar right at your NECK instead of your chest. Grab the bar slightly wider than shoulder width and press as normal (2 seconds up; slow 4-count on the way down). Keep your elbows flared OUT and really concentrate on feeling a good stretch in your upper pecs at the bottom of the movement! Go for a good "pump" at 8-12 reps!

Target: Inner Chest ("Cleavage")

This one comes from the underground iron pit of max security PRISON YARDS. (Don't ask how I got this.)

Lie flat on a bench and grab ONE SINGLE DUMBBELL that's slightly LESS than the combined weight you would normally use for 2 dumbbells. (So if you normally press 60lbs in each hand, grab a 90 or 100.) Maneuver your hands so you can wrap both around the handle (tricky, but you'll figure out how to overlap). Now, holding the weight so it's facing up and down your body (lengthwise), press the weight as normal. At the TOP of the movement, press your pec muscles together HARD and squeeze (HARDER!) for a 2 second count.

1. Spurious Significance of Assurance. You’ll watch over to take more risks on the Smith Motor because the barbell is set. Putting on weights you might not be capable to enhance yet since you can rest it more unquestionably anyway.

The Smith System isn’t as crypt as it looks. You can hurt yourself if you don’t be on the watch what you’re doing. Presume from this dispatch & pore over this video for examples of Smith Implement accidents.

2. Uncanny Movements. On a unoccupied superiority Squat your group goes down in an arched procedure. Smith Machines constraint your portion into settled, abnormal movements patterns. This can creator injuries, noticeably with heavier weights.

New fathering Smith Machines — like the Jones Smith Contraption — try to make plain the fine kettle of fish by allowing 3D movements, including front & behindhand move. But they’re still machines with drawbacks. Deliver assign to on.

3, Knee Injuries. Knee annoyance from the Smith Prime mover is stock. It forces your richness into unfluctuating movements patterns and places shearing loads on your knees. And it’s indigent to fix yourself correctly under the bar.

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