What happens to your body when you STOP lifting weights but keep light cardio? Say all other factors stay the same --e.g. diet, sleep etc. What happens to your body when you stop doing cardio--all other factors stay the same? Just wondering, I saw that documentary Twisted Sisters --I was wondering what happens when body builders STOP lifting -- what happens to their body after they stop competing?
Based on my experience, you'll lose some of the muscle weight you put on (but not all of it, especially if you added a lot of weight), and a lot of your strength, but not all of it.
At one point in my life, I went from 130# to 168# over about 4 years of steady lifting. Probably doubled my strength. Then I had to take 4 years mostly off (I lifted a bit in the summers). At the end of that time, I was still 152#, and still quite a bit stronger than when I first began lifting.
It seems to me like my body had determined a new set point for my body weight of around 150#, instead of around 130# which is where it was until I was 25 and started lifting.
That's my n=1 data on this
If you learned how to speak a foreign language, moved to an area replete with speakers of the language, achieved a degree of fluency, and then moved away and stopped speaking your new language you would gradually lose your ability (although it would likely never return to "O").
The same thing happens with exercise.
You could also imagine a three legged stool where one leg represents sleep, another exercise, and another diet. If the three legs are relatively balanced, you could easily sit on the stool. However, remove one leg, or dramatically change it's length, and you will have a hard time staying seated, you might even fall off. You'll eventually find a new equilibrium (even if is lying face down on the floor), but the overall picture will definitely change.
You create neuromuscular connections (links between your nervous system and muscle fibers), neural connections (connections between brain cells), and specific tissue remodeling (bone, muscle, tendon) when you lift weights. These changes are mediated (controlled/created) by hormone secretions, piezoelectric effects (the electric charge created by pressure), and immune system processes that respond to the specific stimuli of exertions approaching your 1RM (1 repetition maximum, a measure of exercise intensity).
You take away the stimulus, you take away the response.
You may not notice an immediate change in "size" or appearance, but on a cellular level the changes start happening rather quickly (in some studies the onset of atrophy begins in as little as two days.)
Just look at what happens to astronauts or bed-ridden hospital patients for dramatic examples of how quickly we can become deconditioned.