X-O to Grow

Many of the biggest bodybuilders use X-Only sets to develop extreme mass.

In our X-Rep writings one of the crucial concepts is max-force production. A target muscle achieves that important fiber-activation ability when it is semistretched—that is, not quite to full elongation. A good example is when you’re just out of the full arms-extended position of a pulldown or chinup. That’s the turnaround, where the negative stroke reverses to positive.

So If the turnaround is the best spot on an exercise’s stroke for fiber activation, why do any full-range reps at all? Good question. In fact, a lot of the biggest bodybuilders use X-Only sets to develop extreme mass.

For example, Jay Cutler, the current Mr. Olympia, begins his chest workout with presses on a Hammer machine—and each of his sets is a series of X Reps, no full-range reps at all. The thing is, he does 12 or more reps per set. Why? To keep the tension on his chest going long enough to trip the hypertrophic switch.

That’s not to say that lower-rep X-Only sets would have no benefit. As we’ve pointed out, training with heavy weight and lower reps builds the myofibrils, the actin and myosin pairings in the fibers. In fact, top researchers Stephen Fleck, Ph.D., and William Kraemer, Ph.D., declare the semistretch position to be where those actin and myosin pairings line up best, so you get ideal size stimulation in those force-generating strands. X-Only appears to be the perfect way to blast the myofibrils into new growth.

Another top bodybuilder who uses that rep style is ’10 NPC USA champ Jason Huh. He recently adopted a heavy-weight X-Only protocol on most of his sets, and he’s gotten a lot bigger and harder. He attributes much of that new size to more stretch-partials sets in his training.

He strives for continuous, controlled tension in the stretch position of the exercise using as much weight as possible. Heavy means a minimum of eight reps, and you get to do absolutely no bouncing or jerking. Also, to avoid joint, tendon and/or ligament injury, he stops short of a 100 percent stretch position.

For example, he does pulldowns, starting with the arms slightly bent and pulling only halfway down, then controls it back up to almost complete arms extension—but not quite—and goes back down to the halfway mark again.

Plenty of research shows that overloading the muscle when it’s close to its stretch position is key to jolting new muscle size. The animal-based study we discuss on pages 33-34 of our e-book X-Rep Update #1 produced a 300 percent increase in muscle after one month of stretch overload as the only stimulus. That’s a triple-size muscle increase—and very little movement was involved.

So heavy, lower-rep X-Only sets can build size—but, as we’ve explained, it’s primarily myofibrillar growth. If you want ultimate muscle size, you should also strive to expand the sarcoplasm, the energy fluid in the fibers.

How? Include some higher-rep, full-range sets, 4X sequences, drop sets or X-centric sets, to name a few sarcoplasm-friendly techniques. Even higher-rep X-Only sets can build sarcoplasmic size. Hey, they’ve helped make Jay Cutler Mr. Olympia. Try some X-O to grow.

—Steve Holman and

Good read