What you see in the mirror does not count.
Focusing only on limited objectives such as getting the biggest chest or the biggest biceps is the worst muscle gaining error and can create anatomical imbalances. Thousands of people spend hours doing endless bench presses and curls to build up the muscles they see in the mirrored walls at the gym. You see these people every single day. What they are refusing to hear is that while they are focusing all of their efforts on these exercises, they are creating an unbalanced tightness in the front of the shoulders which is just asking for rotator cuff issues.
Another example: Everyone in the gym seems concerned about their abdominal muscles but nobody is working the back extensors that work opposite of and support these abs. That’s why you may see guys with six-pack abs and lower back problems.
Loading on the weight doesn’t matter if you are sacrificing form.
Never sacrifice proper form for added weight. When you use too much weight you compensate by throwing the bar, relying on momentum which will not help you. I was recently asked to observe a bodypump class and I couldn’t believe how many people were using so much weight, the bar was all over the place. In many instances, the weights were controlling people to the point that they were losing balance and certainly losing form. This is a huge muscle gaining error.
All movements in weight training must be slow, controlled and steady. Good form and a slow pace ensures that you achieve the full range of motion including slowly returning to the resting position. This is important to exercising the entire muscle. So while you may think you are impressing people with heavy weights, you are not going to see the muscle gains that you expect.
Lowering the weight and going slower will enable you to sustain the load throughout the entire range of the motion and will exhaust your muscle much faster, which is the ultimate goal. That, along with proper rest between workouts along with good nutrition, allows for optimal muscle gain.
More is not necessarily better
I see many guys at the gym every single day, working the same muscles over and over. When it comes to muscle gain, more is definitely not better. Muscles respond to optimal overload and then rest. If you have trouble getting though workouts, your muscles are sore prior to starting and you are not making the muscle gains you were expecting, you are most likely over working those muscles and it may be best to scale down the workouts. Too much training can actually cause muscle loss.
You should never do the same workout two days in a row unless doing low intensity workouts such as yoga and not working your muscles to exhaustion.