by M. Doug McGuff, MD
We have spent most of this book talking about what one should do while in the gym. Of equal importance is the time you spend out of the gym. While the workout itself is responsible for stimulating changes in your body; it is actually your body itself that produces those changes. We must always remember that the changes we are asking the body to make are metabolically expensive. Let us say, for example, that we want to add a pound of muscle to your body. Picture a pound of ground beef at the grocery store. That is a lot of tissue for your body to synthesize. For your body to mobilize the necessary hormones and nutrients to serve the DNA-driven process of protein synthesis, it will require something very basic: time.
How much time is a critically important issue. Exercise can not only serve to stimulate physical adaptations, it can prevent them. Stated differently, if you bring the exercise stimulus back to the body before it has had time to make its adaptation, you will actuallly interfere with and prevent the response from occuring. The point in time when your body finally makes its adaptation is the earliest point in time when it can productively receive the exercise stimulus again. Any sooner, and the exercise will only short-circuit the adaptation process. If you workout too soon, you will know that you have done so because you will actually be weaker in your workout rather than stronger. You will not be able to lift the same amount of resistance for as long as you did in the last workout. If you have waited long enough, you should be stronger on every set of every movement in your workout. We have found through experimentation that 4 days is the minimum that the most average adults will require between workouts. Some people may require as many as 9 or 10 days. In general, the vast majority can recover sufficiently in seven days.
A concern that many might have is that if 4 days is adequate for them, will 7 days be too long? In other words, will there be decompensation during those extra three days? In my experience the answer is: no. We again must remember that the adaptation we are making is to a relatively severe stimulus and the changes made are metabolically expensive. We are building muscle tissue and upregulating metabolic systems which support the functioning of this new tissue. Because of the expense of this process, the body does not seem to allow these adaptations to deteriorate quickly. You do not spend a year building a house that you expect to crumble to the ground over the next year. In a similar way, your body does not make expensive investments that it expects to deteriorate quickly. If a person has been working out for 20 weeks or longer, deterioration may not begin for as long as six weeks. But even in beginners, if 4 days is adequate, 7 days will not be too long. Other forms of exercise (such as jogging, biking, etc.) have shorter deterioration periods. When an exercise stimulus is less severe, the resultant adaptation is less well preserved. Adaptations from jogging or other "aerobic" type activities will start to reverse within 48-72 hours.
In general, at Ultimate Exercise, my personal training facility, we have found that 7 days is a long enough respite for just about everyone and is too long for no-one. You may be tempted to sneak in extra exercise, but remember your body makes adaptations when you are out of the gym, not when you are in the gym.