Q: I can’t wrap my head around lighter weights getting me as big as heavy weights. Wouldn’t fatigue from high reps cause you to stop a set short before you get enough fibers involved?
A: Fatigue from high reps is the very reason they are as hypertrophic as heavy training…
Henneman’s Size Principle of Muscle Fiber Recruitment says the slow-twitch fibers dominate the early easier reps, and as they fatigue, the fast-twitch fibers begin to take over…
So toward the end of a high-rep set, you’re firing mostly fast twitch, as the slow have run out of their energy substrates, like oxygen…
Fatigue helps shut down the slow-twitch fibers, which forces the fast-twitch to dominate. In case you need some science speak for verification, here’s researcher Chris Beardsley’s take…
When lifting light loads to failure, few motor units are initially activated, but as metabolites accumulate and cause fatigue, high-threshold motor units are recruited in order to compensate for the reduced capacity for force production in the working muscle fibers. Similarly, bar speed is initially quick, but as fatigue occurs, bar speed involuntarily slows down. By the end of a set to failure, light loads cause 1) activation of fibers attached to high-threshold motor units, and 2) enough actin-myosin bindings to form simultaneously.
Multiple studies show that lighter high-rep training produces the same amount of hypertrophy as an equal number of sets using heavy loads…
As Beardsley notes, “Programs using 3 sets of the same 7 exercise to muscular failure, but with lighter loads (25 to 35 RM) or moderate loads (8 to 12 RM) [produced] the same amount of hypertrophy.”
While using lighter weights requires more reps overall, you’re reducing heavy wear and tear on your joints as well as getting less cortisol from that stress…
Plus, I believe that ectomorphs get additional size benefit from a lot of low-threshold activation against resistance. That’s due to growth in their abundance of slow-twitch fibers. As I mentioned in Old Man, Young Muscle, researcher Jerry Brainum said that slow-twitch fibers have shown more growth potential than previously thought.
I’m sure all of that is why I was able to achieve my muscular results as a 62-year-old ectomorph with only a 50-pound PowerBlock dumbbell set, an adjustable bench, and a doorway chinning bar. And my workouts only took 35 minutes three days a week…
So for me and my limited home gym, the higher-rep growth results were a godsend. Otherwise, I may have quit to work part-time as a flag pole.
New: Get the ideal exercise for each muscle, the best add-on moves for ultimate mass, complete 35-minute workouts, exercise start/finish photos, and details on building muscle fast and efficiently in Old Man, Young Muscle.
And you still get The Muscle-On, Belly-Gone “Diet” ebook FREE for a limited time when you add Old Man, Young Muscle to your mass-building library. Go HERE.
Till next time, train hard—and smart—for BIG results.
—Steve Holman and Jonathan Lawson
www.X-Rep.com
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