No question is ever silly Condor-the-bird!
The science behind moving from heavy to light weight (and vice versa) is called muscle confusion. We all have our goals that we'd like to focus on and sometimes that requires us to work more within one training approach over another (with just minor tweaking here and there) for an extended period of time before we switch out to something else.
But even the best program out there that matches your goals perfectly will eventually get a little easier because your muscles get good at adapting more and more quickly. So that's when you have to shock them by changing your routine around entirely. This not only confuses them to the point where they have to work (and respond) hard to figure out where your going with them but it also allows them to recover from the repetitive stress patterns that are placed on them from one specific training mode/approach.
It's no different than switching to a new shampoo for a brief period of time when your absolute favorite shampoo is starting to not deliver your hair the same great benefits as quickly and efficiently as it once did. You give it a break with something else and then when you come back it's right back on point and performing optimally again.
You might also notice people CONSTANTLY changing up their program verses just once in a while. This has many purposes varying from beginners to performing athletes, but in general it's done a lot once someone has reached their goal(s). They "random" approach will just shock up each and every workout to keep their body and muscles responding and always working hard "on alert".
I personally like to change everything up in this way: Train heavy for about three weeks, then do a full week of random, then train light for three weeks, then do a full week of random. Of course I deviate from that too but this is how I like to do it most of the time.
So yes, as you can see, you can switch between the two without losing muscle strength.
Hi, Cathe,
I have been lifting weights for a couple of years now and like it immensely. I like your routines very much.
I see that the approach varies and sometimes you lift up to 50lbs (for legs), sometimes stick to as little as 8lbs (for the very legs). I see that in the first case the number of reps is smaller and the two approaches have different goals (strength vs. endurance), but still I wonder whether I can switch from heavier weigths to lighter without losing strength and muscle mass?
Maybe the question is silly, but still I'd like to know the science behind moving from lighter weigths to heavier and back.
