The truth is this, if your max bench is 135 lbs, your chest is almost non existent but by the time you can bench 225 lbs you have at least something, by the time you can bench 315 lbs your chest is substantially bigger and by the time you can bench 405 lbs pretty much your entire upper body is substantially bigger and by the time you can bench 495 lbs you are looking pretty big for sure (with 20'' arms and stuff) also you should improve your squat and your deadlift, by the time you can squat and deadlift 750 lbs your legs are pretty big
This is true. When a muscle gets bigger it gets stronger in the sense that it increases it's contractile force. This should be obvious. When a muscle gets bigger it either increases the size of the individual fibers (hypertrophy) or increases the number of fibers (hyperplasia). Both of these conditions result in an increase in contractile force. Conversely, if those fibers start to shrink or waste away they atrophy and the ability to contract decreases. These are just objective facts not subject to debate.
The confusion lies when strength is defined not just by the ability of the muscle to contract but by the function ability of the body operating as a whole. Generating force, moving a weight, say in the case of performing the bench press, there are so many other factors involved other than pure muscle strength to move a certain amount of weight that it is meaningless to compare two different people. Difference in arm length, neurological efficiency, techniques, tendon strength, skill in the movement... it goes on and on. The only meaningful comparison you can make is to yourself. So whether you are strong or weak "for your size" is not as important as the ability to progress in resistance. If you are an experience trainee, all the peripheral factors: skill, leverage, neurological efficiency, technique... are now held constant. The only factor now for that particular individual is increasing muscle size and strength which is directly correlated.
So though two people may be able to bench press 315 lbs can easily have a dramatically difference in musculature, one thing that you can be certain in both cases, that when each individual started benching at, say, 135 lbs, they had noticeably less muscle mass than they now have benching 315 lbs.
