That's Fit

I've heard this one a lot and although some people swear by it, the research just isn't backing them up. In fact, according to the University of Alabama, the best muscle building occurs when the "up" phase (or contraction) part of the exercise is performed as quickly as possible (while maintaining good form, of course) and then the lowering is done in a slightly slower (and very controlled) way. So, as a general rule, slower reps add up to nothing but longer workouts.

Myth #2
Eating more protein = building more muscle
Um, not necessarily. If you're doing a lot of strength training, your body will need some additional protein from your diet in order to build and repair muscle mass, but it will take what it needs and then whatever is left over will either be excreted or turned into fat stores.

Myth #3
Leg extensions are safer than squats
If you know what you're doing then both of these moves are safe but for the purposes of this post, the reason this myth isn't true is that research shows that exercises that activate more than one joint at a time are safer than those that isolate a single joint. Mainly this is because of the strain that can be put on joints if the isolated muscles aren't activated exactly together, and doing a more dynamic move that involves several joints, like a squat or a leg press, naturally maintains more balanced muscle activity.

Myth #4
Never exercise a sore muscle
In some cases, if the muscle is only slightly sore, doing something aerobic that includes stretching and even a little light lifting can help alleviate the soreness by stimulating circulation. The rule of thumb: If the muscle isn't sore to the touch and you have full range of motion, work it out lightly. But if the muscle is sore to the touch and/or you don't have full range of motion, then give it another day or two of rest.

Myth #5
Stretching prevents injuries
Although in some cases stretching will help prevent injury through increased flexibility, the truth is that most injuries occur within the normal range of motion and warming up is what really makes the difference. Stretching is great for lots of things, but having nice warm muscles is what will save you from getting hurt the most.

Myth #6
The Swiss Ball is better for working the chest than the bench press
Again, it depends. The reason the Swiss Ball is so popular, according to some experts, is because the people using it are so much weaker to begin with. In a perfect world, the Swiss Ball would just be used work on the abs and to build up to using the bench press.

Myth #7
Free weights are always better than machines
Free weights have a lot of great properties and are the choice of veteran strength trainers for a reason but for many people, weight machines can have an awesome set of benefits too. Machines can better isolate muscles and muscle groups, plus the weight can more easily be adjusted for beginners (i.e. if you're not strong enough yet to do a pull-up you can start with a lighter resistance on a lat pulldown machine).