Way too many people go to the gym week after week, month after month, and never see changes. Or, after the first few months of going from doing NOTHING, to doing SOMETHING, their body has changed... but then all the changes STOP. They call it a plateau, they blame it on their diet, they blame it on not going often enough... But in reality, their cessation of progress is because they keep ASKING their body to change.
As soon as they stopping ASKING for change, and start DEMANDING it.... their body finally starts to listen!
Just because you are exercising, doing something more than nothing, doesn't mean your body is going to respond. You see, from the neck down, your body ONLY understands "survival... stimulus, and response". The brain does all the thinking. The brain makes all the decisions. The body ONLY responds. It's deaf to suggestion. It ONLY responds to DEMAND.
Quite simply... the workout you did last week, and the week before, and the week before... is no longer a challenge. If your goal is to add more muscle, you must force that gain. If your goal is to burn more fat, you must force that change also (with nutrition FAR out-impacting training). Lifting the same 15# dumbbell 15 times, just like last week... will result in keeping your arm exactly where it is. If instead, you force (through willpower of the mind) that arm to lift that same 15# dumbbell a few more times, or push upward to a heavier dumbbell... the body is FORCED to adapt. Getting into the science of hypertrophy is outside the scope of this blog post... but trust me, if you don't push OUTSIDE of your current "comfort zone" with the weight you are lifting, your body will NOT change. ONLY after you dig deep enough with your mind to convince your burning biceps that they CAN do 2, 3, 5 more repetitions, despite their protests... only then will they grow. If you can comfortably walk at 3.5mph for 30 minutes on the treadmill... you're NOT forcing your body to adapt, so you're not changing. If moving the treadmill up to 3.8 is fine for the first few minutes, but gets borderline MISERABLE after 20 minutes... congratulations! You're back making progress!
Obviously, you cannot continue to lift more and more weight week after week, and year after year. Eventually there's a point where you just can't run any faster, and there's a limit on how many hours you can train in a week! There is a maximum amount of weight you can lift for your current body-weight, and actually a genetic maximal muscle size for all of us. But 99.9% of us haven't come anywhere CLOSE to those limits, and the freaks of "nature" you see walking among us who lift freakish amounts, more times than not have "altered" their genetic limits with hormonal help.
For the other 99% of us, simply exercising session after session well within our "comfort zone" will AT BEST... simply keep us where we are. As we get older, your comfort zone workout will result in gradual decline.
Push yourself above and beyond your comfortable exercise level MOST workouts. On your "off" days, strive to simply do lo less than your last session. On your "good" days, PUSH beyond, PUSH outside that comfort zone... And find new levels of RESULTS!