Well, it is, or was, whenever you first began weight training. It may also have been after you took a long vacation or simply took a break from training for one reason or another. The point is, it is whenever the muscle has never been conditioned or when it has been allowed to decondition itself during an extended lay off.
The optimum time for training is when the deconditioned muscle has retained the additional myonuclei from previous training, but has lost enough of the protective connective tissue to allow growth promoting microtrauma. HST takes into account this need to apply the growth stimulus when the muscle is most receptive. We call this Strategic Deconditioning.
Training after Strategic Deconditioning results in much more rapid gains in size and strength. This phenomena lead to the idea of "muscle memory". When done properly not only do you quickly regain previously attained size and strength but you will put on new muscle and reach new levels of strength beyond your previous plateau.
Strategic Deconditioning Defined
What does strategic Deconditioning mean and how do we apply it to continue growing? Strategic deconditioning is simply a period of time free from training which is long enough to allow a reversal of some of the acute adaptations in muscle tissue, referring specifically to the repeated bout effect. This usually requires 9 - 12 days straight with no training.
The term strategic is used because this 9 - 12 day period is not chosen at random or whenever you begin to feel "burned out" or even simply lose interest. It is done every 6-8 weeks depending on whether you finish your cycle with 5 rep work or with eccentric work respectively.
You're Not Recuperating
Don't confuse deconditioning with recuperation. Recuperation denotes a restoration or re-building of the tissue. This is what your average personal trainer commonly advocates. He or she will tell you, "Give the muscle plenty of time to rest before you train it again." This pattern of training will not only produce slower gains but you will inevitably plateau more quickly, albeit a fully recuperated plateau. Your muscles will be fully recuperated within the first 7 days of the deconditioning period.
At 7 days you will also still retain most of the repeated bout effects. Additional down time is required to allow the muscle to lower it's defenses. 9-12 days is just long enough to allow deconditioning, but to prevent undue muscle atrophy.
Equally important as the deconditioning period is what you do during the 6-8 weeks of training. Standard practice is to split up your body into muscle groups and train each one separately or in groups on different days. This usually means training a given muscle once or maybe twice per week.
If you were to train this way during the 6-8 weeks before your Strategic Deconditioning period you would be sorely disappointed in the result. This would only provide three workouts every 5 weeks, certainly insufficient to produce a growth promoting environment. Instead of traditional training practices you must use HST techniques to create a consistent environment that the muscle must adapt to by growing larger and stronger.
Full Body Workouts
During the 6-8 weeks of training you will do full body workouts utilizing only 1-2 compound exercises per muscle group as outlined in HST. For example, for legs you will do either squats (or leg press) and leg curls. For chest you will do incline bench and weighted dips. For back do wide grip bent over rows and close grip weighted chin ups or pull downs. Pick one or two shoulder exercises that hit your weakest area and one exercise for biceps and one for triceps.
You may alternate exercises for each muscle group from workout to workout. By alternating exercises from workout to workout you can utilize more exercises over the course of the week. This isn't necessary for growth, but many people chose to do this with great success.
Each and every workout you should increase the weight you use for each exercise. This means 5-10 pound increments for upper body and 10-20 pound increments for legs. This obviously requires that during the first week you are not using your previous cycle's max loads.
If the Strategic Deconditioning is done properly, you won't need to. To choose a starting weight for your exercises, go backwards from the weights you finished with at the end of the previous cycle. Allow for 6 increases in weight with the last increase being slightly above the previous cycles finishing weight. Once again, more details can be had by reading the original publication of HST.
It is this practice of frequent loading followed by Strategic Deconditioning that allows a person to reuse submaximal poundages to elicit new muscle growth.