Doping is a serious concern in sports, where sportspersons consume anabolic-androgenic steroids (AAS) to enhance their performance and gain an unfair advantage over their competitors. These drugs’ effect on the human body is similar to that of the hormone testosterone. They stimulate bone and muscle growth, and appetite, making them valuable as medicines to help patients cope with wasting ailments like AIDS or cancer.

Mice study

Now, researchers from the University of Oslo and the Atlantis Medical College, Norway, have found that muscles in mice that have been briefly exposed to AAS display a ‘muscle memory’ that recreates the effects of the drug long after it has been stopped. This mechanism, the researchers suggest, could also let sportspersons who have engaged in doping briefly experience its performance-enhancing effects even many years after.

In muscles, the effect of AAS is called muscular hypertrophy. It is the increase in size of muscle fibres, also known as myocytes, which constitute the cells that make up muscles. Muscle fibres have multiple nuclei. When muscle mass increases, the number of nuclei also increases.

“When mice were briefly treated with steroids the muscle mass and number of nuclei increased. The drug was subsequently withdrawn for 3 months and the muscle mass returned to normal, but the excess cell nuclei persisted,” noted the researchers’ paper, published in the Journal of Physiology on October 28.

These excess nuclei ‘remember’ the effects of AAS when it was consumed. When the mice were tasked after 3 months — 15 per cent of a mouse’s lifespan — muscle fibres in those with AAS-treated muscles grew by 30 per cent over six days. Mice which had been treated with sham-AAS experienced insignificant growth.

In humans too

In humans, Prof. Kristian Gundersen believes there could be a similar ‘muscle memory’ effect, but capable of lasting almost an entire lifetime. Prof. Gundersen was the lead researcher, from the Department of Bioscience at the University of Oslo. His next course of action is to directly measure if there is such a latent hypertrophy in humans. Earlier, in 2010, Prof. Gundersen had led another study that had found that the benefits from exercising at a young age induced a similar ‘muscle memory’ that could help people stay fit with lesser exercise as they grew older.

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