I received 2 e-mails this week, and both relayed the same problem. Jack says, "I can never get my bench press above 300 pounds or my squats above 400." Jill asks, "Is there a plateau? I seem to reach some points I just can't exceed. I'm at my best visual bodyweight -- 140 pounds -- but I still can't help but think I should be adding plates." At a bodyweight of 158 pounds Jill "has more strength, but does not enjoy the extra 18 pounds". At a bodyweight of 137 she "was not able to leg-press 200 pounds and my upper body strength also waned."
To me, symmetry and balance are the most important elements of a physique. In the human body the basic determinant of the overall proportions is the skeletal frame. Not only height and weight, but the amount of muscle come into play. Humans, of course, come in an infinite variety of body types. There are people who are tall, thin, and muscular, like a wiry greyhound. And there are others who are large, thick-boned and heavyset, like rottweilers. If you were to imagine rottweiler muscle on a greyhound frame, you get an idea of what constitutes too much muscle.
For the sake of discussion, let's assume we're talking bodybuilding; not powerlifting. Not fitness. As I practice bodybuilding, it is to create something visually pleasing, something that will get a positive response from the viewer. But different viewers have different tastes, so how do I determine what's attractive?
My guess is that both Jack and Jill have optimized the amount of muscle each is designed to carry. That amount of muscle can lift only so much weight. You can call it a plateau, or give it another name, but Jack's numbers sounds like about his limit, unless he were to ingest massive amounts of steroids. Even then, I don't think Jack would go much beyond the limits he's established at this point.
I remember watching Bill Pearl and Arnold train away with squats in the 350-pound range. You can't go on forever increasing your poundage, because there are limits for each of us: Muscular limits, connective tissue limits, tendon and ligament limits, and skeletal limits. What will usually stop you in your quest for ever-increasing poundages will be the amount of muscle mass your framework can carry.
How do you know when you have reached that point? When you start to look BIG. When you look in the mirror and the impression you get is big, you are carrying too much muscle for your frame. If that's what you want, great! But if the impression you get after looking in the mirror is neither big nor thin, then chances are you're carrying the right bodyweight. And that bodyweight -- that combination of skeleton, connective tissue and muscle -- can lift only so much weight.
When I judge physique contests I do it in much the same way they judge dog shows. This may sound a little strange, but bear with me: The body which comes closest to balancing the muscle mass with the frame always scores higher with me than those whose muscle mass overpowers their frame.
Once this basic element of symmetry is achieved, then you should turn your attention to weak bodyparts to bring them up, and refine the overall musculature. Squats, benchpresses, and leg presses are all overall mass builders and at some point have to be dropped in favor of more bodypart specific movements. So, in the end, my advice to both Jack and Jill is: Are you certain you want the added size heavier poundage will give you? Maybe you should start refining and detailing.