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There is a great deal of conflicting advice for physical training to build new muscle.
Some exercise experts suggest that maximum benefits are obtained by working out every muscle group three times a week. Other trainers tell us that working out any single muscle group more often than once a week is overtraining. There are even some exercise physiologists who call for daily workouts, with one day a week off, for optimum results. Which approach is best?
There Is No Single "Correct" Workout Program
No training program is best for all people at all times. Sometimes it is best to work out every day. Sometimes it is best to work out every other day (three times a week). Sometimes it is best to work out just once a week--although working out less frequently than once every two weeks will result in loss of hard-earned muscle mass.
The suggestion that working out every day gets maximum muscle benefits comes not from the peer-reviewed academic literature of training and exercise physiology but from anecdotal, informal reports from the Frekvensprosjektet, which is Norwegian for "Frequency Project."
The Frekvensprosjektet recruited 16 Norwegian power lifters, 13 men and 3 women. All 16 volunteers were put on the same workout program, except half were told to do the full routine 3 times a week, and half were told to do half of the routine every day, a total of 6 days per week. The 3-day and 6-day workout groups did exactly the same amount of work, but over different time periods.
According to exercise experts Christian Finn and Matt Perryman, at the end of 15 weeks, the three-times-a-week exercisers had gained, on average, 5% more muscle strength. One participant in this group failed to make any gains at all, and one participant gained 10% muscle strength.
In the every-day workout group, the average gain in muscle strength was 10%. The participant in this group who had the least improvement still had about 6% greater muscle strength at the end of the program, which was more than the average gain in the other group. The average gain in this group was about the same as the greatest gain in the other group, and one participant in the every-day workout group gained 15% new muscle strength.
However, there were people in both groups who actually lost muscle mass, that is, there were people who worked out on both schedules whose muscles got smaller, not larger. There are also reasons not to try to apply these results to most people who are simply trying to get back into shape.
What Works for Elite Athletes May Not Work for You
In the Norwegian Frequency Project, the average age of the athletes was 21. All of the athletes had participated in international competitions. Moreover, physiologists have found that the muscles of elite athletes and people who don't exercise regularly build new tissue very differently.
When elite athletes work out, their muscles build new fibers from protein for 24 to 48 hours. When non-athletes work out, their muscles build new fibers, which make them stronger, for just 12 to 16 hours.