The Open Sports Sciences Journal

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Changes in Isokinetic Muscle Strength in Adolescent Soccer Players after 10 Weeks of Pre-Season Training

Michal Lehnert1, Petr Stastny2, James J. Tufano2, *, Pavel Stolfa1
1 Palacky University in Olomouc, Faculty of Physical Culture, Tr. Miru 116, Olomouc, Czech Republic, 77111
2 Charles University in Prague, Faculty of Physical Education and Sport, José Martiho 31, Prague, Czech Republic, 16252



During soccer-specific movements, the strength of knee extensors and flexors is of great importance and achieving certain strength ratios between the two has been identified as an important parameter for reducing the risk of soft tissue injuries around the knee.


The aim of the study was to evaluate changes in isokinetic strength of the knee flexors and extensors and their strength ratios in elite adolescent soccer players.


Before and after 10 weeks of standard pre-season soccer training with progressive eccentric hamstring exercises, the players (n=18; age 17.1±0.4 years) participated in isokinetic testing to assess concentric and eccentric peak torque at 60°·s-1.


After 10 weeks of training, the peak eccentric torque of the non-dominant quadriceps increased (p=0.018; ω=0.24). Additionally, the average eccentric work increased in the dominant hamstrings (p=0.007; ω=0.23), dominant quadriceps (p=0.02; ω=0.31), non-dominant hamstrings (p=0.003; ω=0.25 and non-dominant quadriceps (p=0.01; ω=0.37). Lastly, the isokinetic functional ratio (eccentric hamstrings-to-concentric quadriceps) increased in favor of eccentric hamstring strength in the non-dominant limb (p=0.04; ω=0.31).


The results of the study indicate that pre-season training induced suboptimal changes in the isokinetic strength of the knee flexors and extensors in elite adolescent soccer players. However, the lack of injuries combined with an apparent lack of preparedness explained by slow velocity isokinetic testing indicates that future research should investigate other forms of strength testing to determine soccer-specific preparedness such as isokinetic dynamometry at higher speeds (i.e. 180°.s-1 or 240°.s-1) and traditional weight-room testing such as 1RM tests.

Keywords: Conditioning, Football, H:Q ratio, Peak torque, Training, Youth.

Article Information

Identifiers and Pagination:

Year: 2017
Volume: 10
Issue: Suppl 1: M3
First Page: 27
Last Page: 36
Publisher Id: TOSSJ-10-27
DOI: 10.2174/1875399X01710010027

Article History:

Received Date: 06/06/2016
Revision Received Date: 19/08/2016
Acceptance Date: 10/09/2016
Electronic publication date: 28/04/2017
Collection year: 2017

© 2017 Lehnert et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Charles University in Prague Faculty of Physical Education and Sport José Martiho 31 Prague, Czech Republic, 16252; Tel: +420 777 144 962; E-mail:

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