INTRODUCTION: The myotendinous junction (MTJ) is at high risk of strain injuries, due to high amounts of energy that is transferred through this structure. The risk of strain injury is significantly reduced by heavy resistance training (HRT), indicating a remodeling capacity of MTJ. We investigated the degree of remodeling of muscle fibres near the human MTJ.

METHODS: In eight individuals, samples were taken from the semitendinosus and gracilis MTJ and they were stained immunohistochemically for myonuclei (DAPI), fibroblasts (TCF7L2) and satellite cells (CD56).

RESULTS: A high portion of the muscle fibres adjacent to the MTJ contained a centrally located myonucleus (47±8%, mean ± SD) and half of the muscle fibres were CD56 positive. The number of satellite cells and fibroblasts were not higher than what has previously been reported from muscle bellies.

DISCUSSION: The immunohistochemical findings suggest that the rate of remodeling of muscle fibres near the MTJ is very high. The finding that there was no increased number of satellite cells and fibroblasts could be explained as a dynamic phenomenon. The effect of HRT should be evaluated in a randomized setting. This article is protected by copyright. All rights reserved.