X-Rep training is simply placing a muscle in its completely contracted position, or close to it, against resistance and holding it there until the muscle can no longer contract. Once you achieve fatigue overload, you slowly lower the weight through the eccentric range of motion, and the set is complete. It's a very intense form of muscle overload that's relatively easy to measure - not in number of reps but in seconds.
An X-Rep set should consist of one 20-second contraction and a slow, six-second negative. That's it. For the technique to be most effective, you use it on exercises that place the target muscle in a complete contraction against resistance - a.k.a., the contracted-position movements in the POF training protocol.
To measure the overload , you use a clock with a second hand or a stopwatch, and at each workout you try to hold the weight in the contracted position for a few seconds longer. Continuing with that progression, you eventually reach 30 seconds, at which point you increase the weight at the nest workout to bring your extended-peak contraction back to 20 seconds - usually about a 20 percent increase in weight. The one drawback of this precise calculation is that you have to keep records of each set so you can strive to better your performance at every workout. Remember, overload must be progressive if you want to get the best muscle-boosting effects, so be meticulous.
