Prevent muscle loss with minimal training?

How much training is needed to avoid loss of muscle mass gains?

Gaining muscle mass is a slow process. However, muscle mass can be lost quickly during muscle disuse, for example during prolonged bed rest or when in a cast. A less extreme example of muscle disuse is detraining (i.e. training less or not at all). How fast do you lose muscle if you stop training or when training volume is reduced?

This study investigated the effect of detraining on muscle size and strength gains. Subjects first performed a 16-week resistance training phase. During this phase, they performed 27 sets per week for the quadriceps muscle.  Subsequently, subjects performed either 3 sets per week (1/9^th original training volume) or stopped training at all for 32 weeks.

The subjects that did no training at all during the 32 weeks lost 30% of their muscle size. However, subjects that performed 1/9^th of the original training volume did not lose any muscle size.

As for muscle strength, the group that did not train did not show a decrease in strength. The 1/9^th training group even showed a small increase in strength.

Note that these results were for young adults (20-35 yr). The study also investigated older males (60-75 yr), in which 1/3^rd of the original training volume (i.e. 9 sets per week) did not seem effective to keep gains in muscle size, but 1/9^th of the training volume was effective to keep strength gains.

Study:
Bickel et al. Exercise Dosing to Retain Resistance Training Adaptations in Young and Older Adults. Med Sci Sports Exerc, 2011

Go to the next infographic in the resistance exercise series:
Is muscle growth different between men and women?