This is a great article written by Nick Nilsson. The article introduces techniques on how to reduce muscle size using two-pronged approach: through appropriate training and diet.
If you're looking to reduce muscle on specific part of your body, than you should give it a try. It's really an easy and healthy technique; you don't have to starving or overtraining yourself.
How To Train To Reduce Muscle Size ON PURPOSE
By Nick Nilsson
While this is very rarely the goal with weight training, there ARE people who actually DO want to reduce the size of a specific muscle or muscles (but without just stopping training and losing too much strength). Learn how to do it the right way!
It may sound strange that anybody would want to REDUCE muscle size on purpose, but honestly, if that's one of your goals, you're not alone! Reducing the size of a specific muscle group or all your muscles in general is a more common goal than you might think.
And there certainly ARE ways of decreasing the size of your muscles through exercise! But let me just start by saying, if you feel your calves are too big, please go ahead send them my way... :)
Basically, in order to reduce muscle size, we need to utilize a two-pronged approach. Which are focusing on a very specific training style and then on post-workout nutrition.
For training, we're going to accomplish the goal of reducing muscle size by utilizing VERY high rep sets (upwards of 80 to 100 reps per set!). This type of training can be done with pretty much any exercise you choose and will be dictated by which muscle group(s) you want to reduce the size of.
To properly explain the reasoning behind how this type very high rep training can be effective, you should first know that there are two basic types of muscle fibers: fast-twitch and slow-twitch.
Fast-twitch fibers are responsible for high-power, short-duration activity (like sprinting and heavy weight training) while slow-twitch fibers are responsible for low-power, long-duration activity like jogging, walking and other endurance-based activity...basically anything you can do for longer than a couple of minutes.
Fast-twitch fibers are larger than slow-twitch fibers and when you have a high percentage of fast-twitch fibers, you will have larger muscles. You can see the difference when you look at a sprinter compared to a marathon runner.
So what does this have to do with making muscles smaller? Well, most likely, if you find a specific muscle group too big for your liking, you probably have a high percentage of those fast-twitch fibers in that muscle group. They are much easier to develop and you probably don't even have to work that muscle group to keep it larger!
What you WILL have to do, then, is focus ONLY on endurance-oriented training for that specific muscle group that you want to make smaller. This will preferentially detrain the fast-twitch muscle fibers and train the smaller, slow-twitch muscle fibers.
So how you put this type of training into practice? My best advice would be to pick an exercise or two that work the muscle group you want to reduce. For example, if you want to decrease your calves, standing and seated calf raises will work.
Now, at the beginning of EVERY single workout you do (no matter what other bodyparts you're working or even if you're just doing cardio training), perform 2 sets of VERY high reps (80 to 100 reps) on one of those exercises (you can use the same exercise for both sets or do one set of each). Rest two minutes in between those 2 sets to clear out lactic acid build-up.