My experience has been to use both when training for a specific medium term goal such as 6 to 8. The over training tactic was used in the early preparatory stages of my program aimed at endurance and developing the body, ready for more intense specifics where as the Single Factor theory was used for specific conditioning of strength & power by utilizing Supercompensation in recovery to maximise quality of absolute strength sessions:
What most of us call overtraining is really over-reaching. For most of us, "over-reaching" is what we're really referring to when we say overtraining. Over-reaching-is pushing yourself into a mild state of fatigue with your training. Regression in performance sometimes does occur during an over-reaching period, yet performance rebounds back very quickly, usually above and beyond it's previous level, with a short period of rest or lowered volume (within days). It can be good or bad depending on how you use it.
Overtraining occurs when you chronically over-reach for months or years on end. This leads to performance regression that can take months to recover from. Most athletes don't ever reach a true overtrained state. Another important term is Under reaching.
Under-reaching occurs when you intentionally "take it easy". This is like taking your foot off the gas in your training intentionally. It also can be good or bad depending on how you do it.
It has been my experience that, the reason many people train hard and consistently and don't make the gains they feel they should, is because they spend too much time over-reaching and not enough time under-reaching. This doesn't apply unless you train both hard and consistent. Allot of people don't train hard or consistently and look to answers within the minutia of their or (more commonly) other's program's and they may simply find that a more consistent and focused approach to their own training would deliver far better gains.Over-reaching by design can be a very good thing.
Recovery and Supercompensation:
Recovery can be defined as - regaining what was lost - however, for the climber this is not enough as it returns us only to where we started. Adaptation can be defined as the process of long-term adjustment to a specific stimulus. This process of adaptation can include adjustment in a number of factors such as the climber's physiology, psychology and mechanics. These alterations can ultimately lead to improved performance - which is a more satisfying goal.
We train to get fitness and strength. We want to climb longer harder routes etc. In order to get fit we must stimulate some fatigue so that our body adapts. We must push ourselves beyond our limits some of the time - which is fatigue.
There must be an optimal blend of both fatiguing oneself or over reaching (in order to improve) and resting oneself or under reaching, so that you can see the gains from the over reaching you've done. Under reach too much and you won't get the results you want because you haven't forced your body to adapt; over reach too much and you won't get results because the body is knackered.We have to determine how to intelligently over reach at the beginning of a training cycle, under reach at the end of a cycle, in order to boost the overall results of each training cycle.
Dual factor theory:
The Dual factor theory represent the relationship between fatigue and fitness. One factor is fitness the other factor is fatigue.A stress adaptation model that bases a training plan around the long term relationships between stress and fatigue. When you train you accumulate both fatigue and fitness. However, what many may not realize is that the fatigue that accumulates over the course of a training cyle itself "masks" the fitness gains that you make. However it has been acknowledged, that fitness persists about 3 x longer then fatigue. This means that when all traces of fatigue are gone from a bout of exercise or a cycle of training, the fitness gained will persist for 3 x as long as the fatigue. That's why most people make gains when they take a few days off from time to time.
The Single factor theory:
Is the basic stress adaptation model that is more common, and the model used to explain high intensity training. With this theory you look at physical ability as one short term factor. You load, recover, load, recover - always recovering fully before loading again.
The problem with this approach is you are left with the problem of timing sessions to correspond to the supercompensation wave. Anything sooner or later will lead to a bad session. Another problem is there is only so much systemic stress that can be thrown on the body in one session. If you prolong the length of the stress (loading and fatigue) period by days or weeks, instead of a single workout, you increase the overall stress. Therefore, providing you do allow recovery to take place after prolonged loading, you increase the height of the supercompensation curve as well.
With Supercompensation, one workout represents a period of fatigue. But, in the Dual Factor Theory, up to 6 weeks would represent a period of fatigue. With Supercompensation, a day or two (up to a week) represents a period of rest. But in the Dual Factor Theory, up to four weeks may represent a period rest.