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12-20 vs 4-6RM

Why after cycles of Hypertrophy type 3 x 12-20RM lost mass easy, while after 3-6 sets x 4-6RM the mass remains?

[quote]Paul0 wrote:
Why after cycles of Hypertrophy type 3 x 12-20RM lost mass easy, while after 3-6 sets x 4-6RM the mass remains?[/quote]

I don’t believe there is one answer here, but one aspect is that the 12-20 rep range is mostly working type-2a and type-1 fibers (stamina and endurance fibers) which have the smaller/smallest cross-sectional area. On the other hand, the majority of muscle size comes from the type-2b fibers (fast fatiguing/fast twitch). The 4-6 rep range, with heavier loading of course, is primarily working the 2b’s, but the 2a’s and 1’s are always recruited to some extent.

After the physiology 101, basically if you workout in higher rep ranges you are neglecting to stimulate the fibers that make up most of the size of the muscle. You know the saying, “use it or lose it!” This is also why lifting heavy weight while cutting helps preserve lean mass.

While this aspect of training isn’t absolute (some guys can maintain/gain in the 12-20 rep range) its a general rule of thumb.

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