Even brief usage of anabolic steroids may have long lasting, perhaps even permanent performance-enhancing effects, according to a new study.

It was previously believed that re-acquisition of muscle mass after periods of inactivity was due to motor learning. The new data from an investigation of  the effects of steroids on muscle re-acquisition in mice suggests that there is a cellular 'memory mechanism' within muscle of brief steroid users.

The team investigated the effects of steroids on muscle re-acquisition in mice and discovered greater muscle mass and more myonuclei, which are essential components for muscle fiber function, were apparent after returning to exercise.

The muscle fibers with cell nuclei. Credit: Jo C Bruusgaard

The findings might have consequences for the exclusion time of doping offenders as brief exposure to anabolic steroids might have long lasting performance-enhancing effects.

Professor Kristian Gundersen of the University of Oslo and senior author of the study says, "Mice were briefly exposed to steroids which resulted in increased muscle mass and number of cell nuclei in the muscle fibers. Three months after withdrawal of the drug (approximately 15% of a mouse's life span) their muscles grew by 30% over six days following load exercise. The untreated mice grew insignificantly. 

"The results in our mice may correspond to the effects of steroids lasting for decades in humans given the same cellular 'muscle memory' mechanism. The new results might spur a debate on the current World Anti-Doping Agency (WADA) code in which the maximum exclusion time is currently two years."
Additionally, the data suggests that strength training when young might be beneficial later in life since the ability to generate new myonuclei is impaired in the elderly.

Future studies should include human muscles and further investigation into the cellular and molecular mechanism for muscle memory.