Affiliations: [a] Department of Physical Education and Sport Science of
Thessaloniki, Aristotle University of Thessaloniki, Thessaloniki,
Greece | [b] Department of Physical Education and Sport Science of
Serres, Aristotle University of Thessaloniki, Serres, Greece
Abstract: Isokinetic dynamometers are extensively used to monitor strength
development in young soccer players. The purpose of this study was to examine
the effects of age, velocity and leg of preference on the peak moments in young
soccer players. One hundred and fifty eight soccer players (age = 13.2
\pm 2.1 years; height = 1.6 \pm 1.4; body mass
= 51.6 \pm 14.89 kg) performed maximum knee extension and
flexion efforts at 30^{\circ}/s,
90^{\circ}/s, 120^{\circ}/s and
180^{\circ}/s of both legs and under eccentric and
concentric conditions. The absolute (Nm) and the relative (Nm/Kg) peak moment
of forces were further analyzed. Four-way analysis of variance designs were
applied to examine the effects of age, angular velocity, leg of preference and
muscle action (eccentric -- concentric) on the recorded moments for knee
extension and flexion. The isokinetic moment of force of knee extensors ranged
from 1.01 \pm 0.19 to 3.58 \pm 0.50
Nm/kg. The knee flexion moments ranged from 0.95 \pm
0.16~Nm/kg to 2.42 \pm 0.59 Nm/kg. For all testing
conditions eccentric moments were greater than the corresponding concentric
(p<0.05). The isokinetic moment under all testing conditions
increased significantly (p<0.05) as chronological age
increased from 10 to 18 years. Furthermore, the isokinetic moment of the
preferred leg, collapsed for the effects of age, angular velocity and muscle
action, was significantly greater compared to the moments of the other leg. The
strength profiles developed in the present study can assist in the
establishment of baseline data in young soccer players.
Keywords: strength, knee, isokinetics, soccer, children
