Though there are several bodybuilders and fitness experts who manage to get killer biceps by pressing and pulling, the same technique may not work or others.
For some men, the effects of gymming (muscle growth) can be seen in other parts of the body (chest, legs) but the biceps remain disproportionately small.
There is not one but several reasons why that might happen.
Have a look:
If you restrict your range of motion while working out, the muscle tissues which are responsible for growth get destroyed.
Without a correct range of motion that includes negative parts, your progress will be slow.
Pay attention to the gym trainer while learning an exercise. You might end up doing the things wrong way and your hard work might go waste.
This is probably the biggest blunder one can do while gymming. Everyone around you is on a different level of fitness and mimicking their exercise patterns won't do you any good.
Girls like guys who lift heavy weights, but lifting weights beyond their physical strength can not only hamper growth but also cause injury.
So, your trainer asked you to go all the up while doing crunches but you went only half-way, then you are in for some serious trouble.
If you are doing exercises the right way and lifting weights within your capability, only then the motto "more is better:" is valid.
If your trainer isn't helpful enough, try to learn the right way to do exercises through other means. Know as much as you can about lifting and pressing.
There will always be people who are better than you not only in the gym but in every field of the world. It is advisable to focus on your own growth instead of being insecure by looking at the people who are better than you.