The Most Basic Law of Training

Neglecting the most basic training law results in more failures than all other mistakes combined.
This basic law or principle is the first and most basic physiological concept that needs to be understood by both runners and their coaches who want to optimize short- and long-term performance progress. Unfortunately, precious few runners and coaches follow this basic law of training when designing their respective training programs. Under-estimating the importance of this most basic law will surely result in ineffective training - even if all other training strategies in a runner's program are highly sophisticated.

This training law is an essential part of the "foundation" of the training "house plan." No matter how well-designed or well-furnished the rest of the house (or training plan) is, without a firm foundation, it will collapse. A builder (or runner) can invest heavily in the materials (by working hard) on all of the other parts of the house (specific training strategies) and still have it collapse (or fail to achieve their potential) if the foundation is not strong and supportive (by not adhering to this most basic law of training).

The most basic training law is simple: Each and every training stress should be followed by an amount of rest (or recovery) which is appropriate to allow for optimal performance progress.

Optimal progress or improvement is the result of balancing optimal training stress with optimal training rest or recovery.
Put into an equation it looks like this:
Optimal Training STRESS + Optimal Training REST = Optimal Performance PROGRESS

While almost every runner or coach is aware of this most basic law of training, failure to effectively practice it usually occurs from over-emphasizing the "stress" (or hard work) part of the equation and underestimating the equal importance of the 'rest' (or recovery) part of the equation.

Therefore, understanding what constitutes optimal rest (or recovery) from hard training sessions (or stress) will be the primary goal of this article. We will achieve this goal by providing you with (1) a basic understanding of the physiology of stress and rest, as well as (2) a set of tools, methods and guidelines to help you balance stress and rest for optimal training progress.

Although the concept (stress plus rest equals progress) is simple enough to understand, it can in fact, be very complex. This is because each person's body is different (general health, basic muscle fiber type, body weight, running economy, injury history, fitness level, training history, etc..) and therefore, responds to different types of workouts (long runs, tempo runs, interval workouts, speed sessions, etc.) and other external stresses (sub-optimal weather conditions, altitude, job stress, family commitments, financial concerns, pollution, allergies, inadequate sleep, poor nutrition, etc.) in different ways.

All of these factors make it very challenging to gauge how to best apply certain types of training stress (key workouts), manage various life-style stresses, and use the proper amounts of rest and recovery in order to ensure optimal adaptation that ultimately leads to better running performances.

Rest can not be separated from stress. They are both equally important factors in the same training equation. Stress and rest each are parts of the same whole: making up any complete cycle of effective training.
Whether you realize it or not, rest (or recovery) can be, should be, and is taken after each and every unit of training that you perform. Rest is taken between hard speed repeats on the track. Rest should be, and is taken on the easy day (or days) that follow a hard workout day. And an easy month of rest is often taken (and recommended) after any racing season.

(Source: http://www.runningonline.com)