Affiliations: [a] Laboratory of Coaching, Department of Physical
Education and Sports Sciences, Aristotle University of Thessaloniki,
Greece
Note: [] Address for correspondence: Pr. Christos Kotzamanidis Department
of Physical Education and Sports Sciences, Aristotle University of Thessaloniki
54006, Thessaloniki, Greece. E-mail: kotzaman@ phed.auth.gr
Abstract: Determining the activation of antagonist muscles around the knee
joint in athletic children can provide useful information for the better
understanding of the mechanisms responsible for strength production in athletic
populations during developmental ages. The purpose of the present study was to
examine possible differences on a) concentric and eccentric isokinetic torque
scores of knee muscles and b) electromyographic (EMG) activity of antagonist
knee muscle groups during isokinetic concentric and eccentric knee extensions
and flexions between prepubertal gymnasts and non-athletic children. Ten
gymnasts (age: 9.3 ± 0.8 yrs, training age: 3.4
± 1.1 yrs, mass: 30 ± 3.6 kg, height:
132.1 ± 4.6 cm) and ten non-athletic boys (age: 9.1
± 0.5 yrs, mass: 28.7 ± 3.4 kg,
height: 131.4 ± 3.2 cm) performed maximal concentric and
eccentric knee extensions and flexions on an isokinetic dynamometer at 45, 90
and 180°·s^{-1} randomly. The torque
output of knee extensors and flexors and surface EMG act ivity of vastus
lateralis (VL) and biceps femoris (BF) were recorded. The antagonist IEMG
values were expressed as a percentage of IEMG of the same muscle when acting as
agonist in the same muscle action and angular velocity. ANOVA designs indicated
a significant effect of muscle action on the antagonistic IEMG of VL and BF
(higher during concentric efforts). An effect of angular velocity was revealed
on the antagonistic activity of BF and VL during concentric efforts for both
groups. Additionally, no significant difference on the antagonistic activity of
knee muscles was found between the two groups examined. The present results
suggest that gymnastic training does not affect either torque production or
antagonistic activity of knee muscles in boys aged 8--10 years. However, only a
longitudinal study could determine possible differences on torque scores and
antagonistic activity of knee muscles in gymnasts of various chr onological and
training ages.
Keywords: coactivation, knee muscles, isokinetic, gymnast, EMG, children
