New research has provided a possible explanation for the perceived decrease in endurance musculature as a result of strength training – which could also provide new insights into age-related muscle atrophy.

Researchers at the University of Basel’s Biozentrum in Switzerland set out to investigate what exactly happens in the muscle during training – specifically when it comes to the neurotransmitter brain-derived neurotrophic factor (BDNF) and the effects it has.

The team, led by professor Christoph Handschin, studied the BDNF, which plays an important role in the formation of muscle fibres.

Handschin’s team demonstrated that BNDF is produced by the muscle itself and is capable of remodelling the neuromuscular synapses, the neuronal junctions between the motor neurons and muscle.

The conclusion is that BDNF not only causes the "strength muscles" to develop, but at the same time leads to the number of "endurance muscle" fibres to decline.

“It is interesting that BDNF is produced by the muscle itself and not only exerts an influence on the muscle," Handschin said.

"At the same time, it affects the neuromuscular synapses, which are the junctions between the motor neurons and muscle.

“However, strength muscle growth occurs at the expense of the endurance fibres. More precisely, through the release of BDNF, the endurance muscles are transformed into strength muscles.

"This makes BDNF a factor proven to be produced by the muscle itself and to influence the type of muscle fibres formed."

In a follow-up study, the research group also showed that in muscle lacking BDNF the age-related decline in muscle mass and function is reduced.

“We didn’t expect this result”, said Handschin. “It also makes the findings interesting for treatment approaches for muscle atrophy in the elderly.”

The new knowledge gained about the myokine BDNF will, according to Handschin, provide a possible explanation for the decrease in endurance musculature seen as a result of strength training.

This correlation is already being taken into account in the training plan for high-performance sports. Particularly in sporting disciplines such as rowing, which are geared towards strength and endurance, muscle remodelling must be considered.

• To read the full research, click here for the University of Basel website.