To optimize your training, you need to find the correct balance between training and recovery. Hard training causes immediate fatigue and tissue breakdown. Depending on the difficulty of the training session (and other factors discussed below), you may require from 2 days to 2 weeks to completely recover. Your training session also provides a stimulus for your body to adapt to a higher level (called supercompensation). Training provides the stimulus for your body to adapt, but time is needed both for recovery and to allow your body to adapt and improve.

Turning Genes On and Off

The intensity, duration, and frequency (# sessions per week) of your training all influence the rate at which your body adapts. The adaptations in hormone levels, fat burning ability, capillary density, etc that result from endurance training occur due to repeated training bouts rather than as a result of one workout in isolation. It is as though your body must be convinced that you are really serious about training before making the physiological adaptations that let you reach a new level.

The process of adaptation begins with your genes. Training provides stimuli (for example, glycogen depletion) which turn specific genes on or off. By altering the expression of genes, training changes the rates of protein synthesis and breakdown. For example, endurance training turns on genes for the production of mitochondrial protein. More endurance training leads to more mitochondria in your muscles so you can produce more energy aerobically. Your muscles and cardiovascular system adapt over days and weeks due to the cumulative effect of repeated training.

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Factors affecting improvement

There is great variability between runners in how long it takes to recover from and adapt to a workout. Differences in recovery time and improvement rate are determined by genetics and lifestyle factors. Your genetics determine your predisposition to adapt to training-some of us are programmed to adapt more quickly than others. Lifestyle factors such as diet, quantity and quality of sleep, general health, age (we tend to recover more slowly with age), gender (women’s muscles tend to recover more slowly than men’s due to lower testosterone levels) and various life stressors such as work and relationships all influence how quickly you recover from, and adapt to, training. Because there is great variation between runners in how many workouts they can tolerate in a given period of time, you should not just copy your training partner’s running program. Only through experience will you learn how much training you can handle.

Time Required for Recovery and Supercompensation

Unfortunately, the scientific literature does not provide clear evidence of the amount of time required to realize the benefits of an individual training session. Personal experience and discussions with coaches indicate that 10 days is an adequate amount of time to recover from and reap the rewards of most hard training sessions. Given that any one workout provides only a small benefit (on the order of magnitude of less than 1 %) but that a workout can cause severe short-term fatigue, it is wise to err on the side of caution and allow enough days to fully recover from training before an important race.

The table below provides guidelines for the time required to reap the benefits of 3 major types of workouts. The column “# days before tune-up race or next hard workout” indicates typical amounts of time necessary to fully recover from a workout of each type. Although you will not see the benefits of this week’s workout in this weekend’s race, if you do the workout early in the week you should recover enough so it does not have a detrimental effect on your race performance. The table acknowledges that we often do a tune-up race or the next workout when the fatigue of previous training is reduced rather than when supercompensation has occurred. Only for a goal race do we generally allow enough rest and time to obtain optimal results.

Tempo runs are the easiest to recover from because they do not break down the body as much as the other forms of hard training. Tempo runs are not fast enough to cause much muscle damage nor are they long enough to totally deplete your muscles of glycogen. Long runs have a large degree of variability in recovery time between runners, although replenishing glycogen stores only requires 48 to 72 hours. The variability in recovery time depends both on the genetic and lifestyle factors discussed above and on the type of course (downhills causing more muscle damage and requiring greater recovery time). Interval workouts generally require the longest time to completely recover from because they put your muscles and cardiovascular system under the most stress.

Minimum Time Between Hard Workouts and Races

Type of Workout	Sample Workout	Days before tune-up race or next hard workout	Days before goal race
Tempo run	4 miles @ 10 mile race pace	3-5	6-8
Long run	17-20 miles	3-6	7-10
VO2 max Intervals	6 x 800 @ 3 km race pace	4-6	8-11