THE EFFECT OF QUADRICEP'S FATIGUE FOLLOWING ECCENTRIC AND CONCENTRIC CONTRACTIONS ON FORCE PERCEPTION IN KNEE JOINT

Force perception, as one of the main components of proprioception in neural units of muscles, plays a key part. Considering the spreading trend of sports related injuries in knee joint at times of fatigue, and the differing characteristics of eccentric and concentric contractions of muscles, the purpose of this study is to look into the effects of fatigue after strenuous exercises on the discrepancies that occur in the level of accuracy in perceiving the employed force on knee joint. This research was a quasi-experimental study which was conducted on 20 healthy men with the age range of 18 to 28. In order to measure the maximum voluntary isometric force and certain reproduced amount of it, we used a specially designed dynamometer. The measurements were carried out in two stages with one week interval between them. In the first stage, the muscle’s maximal isometric force (MVIC) and then the accuracy level in producing the target force (MVIC 50%) were recorded. Later, by the protocol of repeated walking up some stairs (repeated concentric contractions), the needed fatigue was achieved. Right after the fatigue, the muscle’s maximum isometric force and the accuracy in producing the target force were measured. In the next stage of our study, the same procedures went on with this difference that implementing the fatigue was done by the protocol of walking down the stairs(eccentric contractions).the data were analyzed in the Even-T system and p<0.05 was adopted. The maximal isometric force in the muscle under examination after eccentric and concentric fatigue dramatically dropped in comparison to the figures before fatigue. The produced MVIC after eccentric contractions, compared with the one after concentric types, was marginally less. The average error rate after both kinds of contraction fatigue was notably high. In addition, the average absolute error in producing the target force in eccentric contractions was higher than in concentric ones. The accuracy in perceiving force is then reduced; consequently, this drop is more obvious in eccentric contractions. Disruption in sense of force might have a role in sports related injuries.