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Front. Physiol. | doi: 10.3389/fphys.2019.01082

Morphological and Mechanical Properties of the Quadriceps Femoris Muscle-Tendon Unit from Adolescence to Adulthood: Effects of Age and Athletic Training

  • 1Department of Training and Movement Sciences, Institute of Sport Science, Humboldt University of Berlin, Germany
  • 2Berlin School of Movement Science, Institute of Sports Science, Humboldt University Berlin, Germany

The combined effects of mechanical loading and maturation during adolescence are still not well understood. The purpose of the study was to investigate the development of the quadriceps femoris muscle-tendon unit from early adolescence (EA), late adolescence (LA) to young adulthood (YA) and examine how it is influenced by athletic training in a cross-sectional design.
Forty-one male athletes and forty male non-athletes from three different age groups (EA: 12-14 y, n=28; LA: 16-18y, n=27; YA: 20-35 y, n=25) participated in the present study. Maximum strength of the knee extensor muscles, architecture of the Vastus lateralis (VL) muscle and patellar tendon stiffness were examined using dynamometry, motion capture, electromyography and ultrasonography.
Muscle strength and tendon stiffness significantly increased (p<0.001) from EA to LA without any further alterations (p>0.05) from LA to YA. Athletes compared to non-athletes showed significantly greater (p<0.001) absolute muscle strength (EA: 3.52±0.75 vs. 3.20±0.42 Nm/kg; LA: 4.47±0.61 vs. 3.83±0.56 Nm/kg; YA: 4.61±0.55 vs. 3.60±0.53), tendon stiffness (EA: 990±317 vs. 814±299 N/mm; LA: 1266±275 vs. 1110±255 N/mm; YA: 1487±354 vs. 1257±328) and VL thickness (EA: 19.7±3.2 vs. 16.2±3.4 mm; LA: 23.0±4.2 vs. 20.1±3.3 mm; YA: 25.5±4.2 vs. 23.9±3.9 mm). Athletes were more likely to reach strain magnitudes higher than 9% strain compared to non-athlete controls (EA: 28 vs. 15%; LA: 46 vs. 16%; YA: 66 vs. 33 %) indicating an increased mechanical demand for the tendon.
Although the properties of the quadriceps femoris muscle-tendon unit are enhanced by athletic training, their development from early-adolescence to adulthood remain similar in athletes and non-athletes with the major alterations between early and late adolescence. However, both age and athletic training was associated with a higher prevalence of imbalances within the muscle-tendon unit and a resultant increased mechanical demand for the patellar tendon.

Keywords: Adolescent athletes, Tendon stiffness, Muscle strength `, muscle architecture, Muscle-tendon imbalances

Received: 05 Feb 2019; Accepted: 07 Aug 2019.

Edited by:

Christian Couppé, Institute of Sports Medicine, Bispebjerg Hospital, Denmark

Reviewed by:

Sébastien RATEL, Université Clermont Auvergne, France
Suzi Edwards, University of Newcastle, Australia  

Copyright: © 2019 Charcharis, Mersmann, Bohm and Arampatzis. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Falk Mersmann, Department of Training and Movement Sciences, Institute of Sport Science, Humboldt University of Berlin, Berlin, Baden-Württemberg, Germany, falk.mersmann@hu-berlin.de
Prof. Adamantios Arampatzis, Department of Training and Movement Sciences, Institute of Sport Science, Humboldt University of Berlin, Berlin, Baden-Württemberg, Germany, a.arampatzis@hu-berlin.de