1. You overtrain and under eat. These are listed as the main primary reason because they go hand in hand and BOTH must be balanced or you can forget growth. The most perfect training regimen will fail miserably if diet is not there to support it. And conversely, the most perfect diet will be wasted if the trainee is doing more workload than they can recover from;most do WAY too much!
2. The training workload is not varied. Doing the exact same lift the same way stops being productive for most trainees within 3-6 weeks. Once the body has adapted to the loading it must be changed if you are to continue to force the body to adapt.
3. Too much focus on isolation exercises, not enough compound work. You can do all the small lifts until you are blue in the face, but until you are moving big poundage in the big lifts you will remain small. Which brings up point #4.
4. You MUST squat and deadlift if you are going to reach your bodies growth potential. Think it through. Doing squats or deads activates 70-85% of the bodies overall musculature in one move. Doing a set of curls maybe 3-5%. Which sends a big signal that the body better get better at synthesizing protein and better at handling the need to grow as a unit? You will NEVER reach your potential without doing the squats and deads.
5. You constantly fluctuate between lifts that have bad carry-over. Here is an example:
I have seen many times, and one I have done myself. The trainee burns out on benching and decides to do Hammer Strength Benches for a change. He makes the switch and is jazzed. His Hammer press is going up every week and he is stoked. After a time he has added 50 lbs to his Hammer bench and decides to go back and hit the bench, only to find its up a whole 10 lbs!!!!!
That doesnt mean there is anything wrong with Hammer Benches. It just means that the lifts are dissimilar enough that an increase in one may not necessarily help increase the lift on another. Use of stabilizers and inter and intra-muscular coordination are two primary reasons, along with neural recruitment pattern gains that don;t apply well to the other lift.
6. You dont know when to de-load/cruise , or take time off. NO ONES body takes a constant pounding of hard training without periods of active or full rest recovery. Until you learn how and when to don this your training will never be optimal
7. Your micro-nutrient support SUCKS! I cant count the number of guys I have seen trying to build great physiques taking one a day vitamin and thinking they have it covered. If you want great things out of your body, you need to put great fuel in it.
8. You train with the intensity of a arthritic old lady. Nuff said.
9. You have no clearly defined goals. Most people just lift to get bigger;, and while this is a fine goal, not having and strength related goals will kill your progress in the long run. Your primary goal should be getting stronger on the big lifts on a CONSTANT basis. Setting short and long-term strength goals and achieving them is what equals a big strong trainee in the long run.
10. You are inconsistent. Getting excited about your training and killing yourself in the gym only to burn out and few weeks later and miss a bunch of sessions ends up being 1 step forward, 3/4 steps backward for many trainees. Getting and staying consistent and racking up sustainable gains over the long-term is what its about.