Last week’s newsletter on fiber-type activation during a set was thought-provoking. If you missed that…
Slow-twitch fibers generate ATP for power via aerobic metabolism—with oxygen (illustration by Larry Eklund)…
Once those endurance fibers crap out during a set, the fast-twitch fibers take over, which creates ATP through anaerobic glycolysis…
In other words, your fast-twitch fibers do NOT require oxygen to contract. They are more glucose fueled, so they dominate on the last few reps of a set…
Bill, my first training partner back in high school, asked if better aerobic conditioning might allow more reps in a given set. Seems plausible…
If the early firing slow-twitch are more efficient, wouldn’t they stay engaged longer, allowing you to perform more reps early on?
Perhaps, but probably not enough to make a difference—if you use continuous tension and a challenging weight, that is…
Tension on the muscle shuts off blood flow to the working muscle, so oxygen in the trapped blood dissipates quickly.
A light weight, on the other hand—30-plus reps—would engage fewer slow-twitch fibers on each rep. So it takes more of those slow-twitch reps to flip the fast-twitch switch.
In that case, aerobic conditioning can make a difference in the number of reps you get.…
Of course, if you pause at lockout, such as at the top of a dumbbell decline press, you allow some oxygen-rich blood flow to the target muscle…
Then, obviously, more reps will be possible with that technique, even with challenging weights.
If you want efficiency—to get the fast-twitch fibers primed and firing fast—do this…
1) Keep tension on the target muscle throughout the set, no resting between reps
2) Do the first set for each muscle with higher reps—but not too high
That warms up the muscle as quickly as possible, which increases efficiency. A primed muscle contracts more effectively than a cold one.
It’s the very reason the STX method has you do a single 15-to-20-rep continuous-tension set close to failure to begin each muscle routine…
While that precision warmup fatigues the slow-twitch fibers and primes the nervous system, it also engages the fast-twitch fibers toward the end of the set.
You don’t have to do multiple warmup sets. PLUS, your second set, after a brief rest, will have a huge hypertrophic payoff.
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