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Heavy HIT: How Often for Fastest Muscle Growth?

Considering my recent rants, some have asked if I’m against heavy training. Not at all. I loved it in my youth; however, being over 50, I’m no longer interested; however, looking back at my experience as well as current research, I’m beginning to wonder if bodybuilders go heavy on too many sets too often…with negative muscle-growth consequences.

The name Mike Mentzer stirs a lot of controversy when it comes to bodybuilding workouts, but he contributed a lot to sensible training—even though I disagree with some of his beliefs. Nevertheless, if we look back at what he found and how he came to his conclusions, even if some were somewhat askew, we can get closer to a few truths that may make your own size-and-strength building efforts much more effective.

Basically, Mentzer believed in short, intense workouts. After he retired from competition, his beliefs went even further in that direction. He became a trainer and eventually had his clients perform only one all-out set per exercise and usually one move per muscle. He also recommended infrequent workouts, often to the point of seeming ridiculous—like every 10 days—but what if Mentzer was right?

He may not have been correct from a maximum-muscle-building standpoint, but perhaps his recommendations were optimal for strength development—that is, building and fortifying the myofibrils in the muscle fibers.

Remember, the myofibrils are force-generating actin and myosin strands in the muscle fibers. The theory is that if they are overly traumatized, for example with slow negatives and heavier resistance, longer recovery is mandatory for complete regeneration. Mentzer’s slow-cadence, heavy all-out sets emphasized the negative stroke, which causes damage to the myofibrils.

Myofibrillar stress may be why his workouts produced exceptional strength increases, even when trainees worked a muscle only once every two weeks—there was optimal recovery of the myofibrils and nervous system. Most of the people he trained got very strong very quickly.

That said, muscle-size gains were less than stellar on Mentzer’s system for most. Could that be because his workouts didn’t provide enough stimulus to the sarcoplasm, the energy fluid in the muscles that can expand via longer tension times and short rests between a number of sets (more volume)? I think yes.

For most trainees the sarcoplasmic fluid, and getting it to expand, is the dominant hypertrophic factor. It’s the “side” of the muscle fiber that is responsible for the most mass. While the myofibrils do contribute to mass, they appear to be more of a strength arbiter than a size producer.

I’ve said that one of the biggest mistakes in bodybuilding is equating strength with size. While strength increases suggest a boost in myofibrillar cross-sectional area, in most trainees it’s not enough to produce extreme hypertrophy. There must be a sarcoplasmic-expansion component—and for most bodybuilders that is what should be emphasized for maximum size.

Taking Mentzer’s theories and results into account, perhaps getting in a myofibrillar-dominant workout every 10-to-14 days would be sufficient for strength and the resulting size in those strands. In between those heavy strength hits should be workouts that produce sarcoplasmic expansion, like the 4X mass method. Those workouts don’t take as long to recover from and also don’t produce as much cortisol, a muscle-eating stress hormone that causes people training too heavy too often to just spin their wheels. Less cortisol is one reason 4X allows more growth.

For those unfamiliar, a 4X sequence is picking a weight with which you can get 15 reps, but you only do 10; rest 35 seconds, then do it again. Continue until you complete four sets, with the fourth set to failure. If you get 10, add a small amount of weight to that exercise at your next workout.

That’s moderate-weight, high-fatigue muscle building that I’ve used almost exclusively now for two years. My muscle size and ability to stay lean are excellent. Would I make better gains using a heavy, myofibrillar-stress-dominant workout every 10 days or so for each muscle?

I don’t know, and I’m not interested in putting my 53-year-old joints to the test. But younger trainees might consider it. I think more strength would be the result—perhaps loads of it, if Mentzer was correct. And you may also get some blips in muscle size; however, I still believe that the sarcoplasm is the biggest contributor to hypertrophy.

Stay tuned, train smart and be Built for Life.

Note: The 4X Mass Workout is available at, as are the two 4X companion e-books with heavy-plus-4X workouts, The X-centric Mass Workout and The Power-Density Mass Workout. All contain full-range Positions-of-Flexion programs.

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