A: We came to the conclusion about nervous system failure after looking at the scientific evidence presented by Steven J. Fleck, Ph.D., and William J. Kraemer, Ph.D., in their book Designing Resistance Training Programs. They discuss a study by Dudley and Harris done in 1992 that demonstrated the activation of knee extensors by the central nervous system during maximal efforts. One of their conclusions was that the CNS “limits force by engaging inhibitory mechanisms that are protective in nature.”
Fleck and Kraemer say that inhibitory mechanisms appear to be especially active when large amounts of force are developed, such as maximal force development at slow speeds of movement. That’s precisely what happens toward the end of a set of eight to 12 reps to failure. They cite studies by Caiozzo, Perrine and Edgerton 1981; Dudley et al. 1990; and Wickiewicz et al. 1984 when they conclude that “neural protective mechanisms appear to have their greatest effect in slow-velocity, high-resistance movements.” Once again, that describes the reps at the end of a set to failure perfectly.
From our experience, it’s the inhibitory mechanisms of the CNS that stop each and every set to failure—it’s the reason you can no longer do a full-range rep. We’ve found that X Reps, due to their shorter stroke at the appropriate point along the range of motion, helps the trainee overcome that inhibitory mechanism to a great degree and tax the muscle much more thoroughly, which is the reason we made the progress we did in only one month with the technique.
We also believe that the reason most bodybuilders have to do so many sets to make even the smallest gains is because of the CNS roadblock. Every set they do, they get CNS failure before enough growth stimulation happens. So the more sets they can do, the more stimulation they get, albeit it’s a very inefficient way to get it because of all the energy it takes for only minor activation of the growth mechanism—the central nervous system stops them early on every set before much stimulation occurs. That’s a sure recipe for cortisol overproduction and overtraining.
X Reps help solve that problem, and they allow you to get much more growth stimulation from any one set. Once we introduced X Reps to our training, we decreased our workload by half and our gains accelerated significantly. In our opinion, and after 40 years of training experience (collectively), we think it’s a true breakthrough.