Tutt

Are you starting out in the gym to 'bulk up'? or have you been training for quite some time but never reached your muscular goals? it could be down to how your training.
I think its one of the most common things to see in a gym - guys pumping out a set of 8 reps in 8 seconds! (maybe exagerated...) This is usually because those people aren't educated about how to actually build muscle, or because they want to show off in front of their friends with how much they can lift. Either way, its not the way to go. So, what is the way? - Time under tension training (TUTT)
You want to utilise the great tool of time - don't rush your reps. Building muscle is all about putting strain (but not too much...don't want to get injured!) on your muscles, and you can't possibly do that if your repping too fast. There is a saying that I have heard - 'momentum kills muscle gain' - and I agree with that. Those people you see in the gym, almost swinging the barbell/dumbbells up, that's not placing strain on your muscles. I'm sure you have seen the other kind of guys though - the ones that are toned/big/strong, that take their time, but most importantly, taking their time during the 'negative' phase of the lift (i.e. the lowering of the barbell during a bench press). That part of the lift is where most strain is placed onto the muscle your targeting, therefore you will 'damage' the muscle far more, so when the nutrition side of your training kicks in, the muscle will grow bigger and stronger.
I have done both styles of training - repping quickly and taking my time, and I can safely say that TUTT is far more effective, but far harder! When I used to train quickly, I never fully got that feeling that I have worked my hardest....that my muscles are 'done' for the day. Usually it was my energy levels that have dropped, rather than my muscles have no more to give. But since switching to TUTT, I get a far better workout, I can really feel the effect it has on my muscles, and the gains have been better.
If you just starting out, or your not reaching the goals you have set, then try switching to TUTT.