| The objectives of this study were to propose a model for exercise-
induced muscle injury by way of a maximal eccentric isokinetic exercise
at low angular speed, and assess the time course of functional recovery
of the injured quadriceps femoris muscle from the maximal voluntary
contraction (MVC) torque and electrical activity (root mean square
- RMS and median frequency - MDF). The effectiveness of the proposed
eccentric exercise in inducing injury was assessed from the activity
of creatine kinase (CK). In addition, the presence of edema of the
quadriceps femoris muscle was assessed by a visual inspection of the
intensity of the magnetic resonance imaging (MRI) signal. These measurements
were carried out before and after the exercise. Ten healthy women
(21.9 ± 1.5) took part in this study. The injury was induced by 4
series of 15 maximal eccentric isokinetic contractions at 5º/s. The
MVC torque reduced up to the 4th day after the exercise (p < 0.05).
The RMS of the vastus medialis oblique (VMO) and the rectus femoris
(RF) muscles decreased on the 2nd (VMO and RF; p < 0.05) and 3rd
(RF; p < 0.05) days after. The MDF of the VMO increased immediately
after (p < 0.05), whilst the MDF of the RF and VL decreased immediately
after (RF; p < 0.05), on the 1st (RF and VL; p < 0.05) and on
the 2nd (VL; p < 0.05) days after. The CK activity increased on
the 2nd day after (p < 0.05). An increase in the intensity of the
MRI signal was observed on the 2nd and 7th days after. In conclusion:
1- the eccentric exercise with low angular speed was effective in
inducing injury, 2- the quadriceps femoris already started its functional
recovery, as shown by the MVC torque and electrical activity, in the
first week after the exercise, despite the presence of an increase
in the intensity of the MRI signal.
KEY
WORDS: Muscle damage, torque, electromyography, magnetic resonance
imaging, creatine kinase.
|
