by Steve Holman and Jonathan Lawson Iron Man Magazine
Q: What’s your opinion of rest/pause training, the way Mike Mentzer used to do it? I’ve read that he did heavy singles with six to 10 seconds between sets and did only four rest/pause singles for each exercise.
A: Mentzer would do a heavy single, rest six seconds, do another heavy single, rest six seconds, do another heavy single, usually with help—that is, forced—rest six seconds, then do one final heavy single with a reduced poundage and/or help from a partner. So he did four singles separated by six-second rests.
We’ve tried that scenario and found it to be excellent for building strength; however, doing singles brings primarily myofibrillar size increases. Those are the actin and myosin pairings in muscle fibers that generate force. The sarcoplasm, the energy fluid, isn’t stressed all that much, even with the short rests, so you leave a lot of mass-building potential on the table.
We morphed rest/pause into what we call X/Pause. For an X/P set you do a standard set to nervous-system exhaustion, hitting failure around rep eight—and you tack on three to four X-Rep partials in the semistretch position. Rack the weight and rest for six seconds; then take the same weight and do an X-only set—that is, do as many additional 10-inch partials through the semistretch position as you can.
So you get a standard eight-rep set to failure for mostly myofibrillar-size stimulation, X Reps for dormant-fiber activation and an X-Only set after minimal rest, which further stresses all of the fibers activated for sarcoplasmic expansion. It’s a very efficient set for an overall muscle-fiber size-building stress.
—Steve Holman and Jonathan Lawson, X-Rep.com