Author(s): RADIC, I., BLESIC, S.1, MILOVANOVIC, S.1, STEFANOVIC, Z.2, MIRKOV, D.2, KNEŽEVIC, O.2, Institution: INSITUT FOR MEDICAL RESEARCH, Country: SERBIA, Abstract-ID: 362

INTRODUCTION:
The maximum voluntary contraction of the forearm muscles and the muscles of quadriceps was tested, as well as endurance in strength at F50% of the maximum intensity of both (injured and non-injured) leg, before anterior cruciate ligament (ACL) surgery, after the surgery, and in the periods after one month, three and six months upon the surgery. We compared recorded signals of force and EMG for all the parameters and both limbs, and compared them with the average values of non-injured subjects. EMG signals along with the hand grip strength test were applied to three forearm muscles: Flexor Carpi Radialis (FCR), Flexor Digitorum Superficialis (FDS) and Extensor Digitorum Communis (EDC) and three muscles of quadriceps: Vastus Lateralis (VL), Vastus Medialis (VM) i Rectus Femoris (RF).
METHODS:
We used wavelet transform spectral analysis (WTS) to quantify force of hand grip and quadriceps muscles and EMG data from same muscles, to characterize force and EMG with WTS peaks as relevant parameters, and to show how those parameters change with knee injury to one leg. WTS is a method comparable to Fourier spectrum analysis (PwS) that has better signal localization in both time and scale (frequency). It is a two-dimensional time series decomposition in both time and frequency, with functions constructed by expanding by time scale and translating along real time of a specifically chosen original wavelet function.


RESULTS:
Differences in force when comparing injured and average values of non-injured participants were not found by using WTS analysis (HG, MVC, 50% from MVC), even if WTS gave us good discrimination in force in quite standing. EMG was the method that gave us more information about muscle activity. It clearly showed which muscle is actived and in what percentage, as well as that the activity of the injured leg is the highest before the operation, while the activity decreases afterwards. The activity is stronger in the right arm and leg (non-injured side and limb) as well as in the average values of non-injured group.
CONCLUSION:
Our results showed that, in addition to being able to see where the injury is by way of use of WTS, it is potentially possible to determine which type of muscle is more or less involved in relation to the part of the body that is injured. In that regard, further researches on this topic can be focused on the use of WTS as as simpler and less invasive methods to detect or understand injury, and its combination with EMG as a more conventional analysis method.