Análise biomecânica em corredoras recreativas com e sem valgo dinâmico durante testes funcionais: efeitos imediatos da fadiga muscular do core

Abstract

INTRODUCTION: Running is an increasingly practiced physical exercise. Core muscle fatigue can influence running performance and modify the movement pattern of the trunk and lower limbs (LL), especially in runners who have dynamic knee valgus. These subjects may present kinematic changes and changes in the electromyographic activity of the LL during functional tests, such as the Step Down Test (SDT) and Y Balance Test (YBT), in addition to muscle weakness. Functional tests can support runners and professionals who care for them to avoid running-related injuries. OBJECTIVE: To compare kinematics and electromyographic activity during SDT and YBT between recreational runners with and without dynamic knee valgus immediately after a core muscle fatigue protocol. METHODOLOGY: The sample comprised 44 female recreational runners and was divided into the dynamic knee valgus (DKV, n=20) and non-dynamic knee valgus (NDKV, n=24) groups. Muscle strength was evaluated to characterize the groups and verify possible differences between them before the fatigue protocol in both groups. The participants were evaluated before and after a core muscle fatigue protocol using SDT and YBT, in which the kinematics of the hip, knee, and ankle in the sagittal plane and pelvic and knee alignment in the frontal plane, and the integral of electromyographic activity were analyzed. (iEMG) of the main muscles of the lower limb during the movement phases in each test. RESULTS: The results for the participants who performed the SDT showed that the DKV group had lower hip extensor strength (p=0.049) and greater hip adduction (p=0.021) than NDKV. Furthermore, this group showed greater vastus lateralis iEMG (p=0.043) during the ascending phase of SDT than the NDKV group. After the fatigue protocol, both groups presented in the preparatory phase a greater medio-lateral displacement of the shoulder towards the supporting lower limb (p<0.05), greater iEMG of the tibialis anterior (p=0.019) and vastus medialis oblique ( p=0.022); while in the descending phase, there was lower iEMG of the medial gastrocnemius (p=0.015); and in the ascending phase lower iEMG of the medial gastrocnemius (p=0.006), vastus lateralis (p=0.012), semitendinosus (p=0.014), biceps femoris (p=0.032) and gluteus medius (p=0.014). The results for the participants who performed the YBT showed that in the frontal plane, the minimum knee angle was smaller (presenting greater dynamic knee valgus) in the DKV group (p=0.025) and the angular excursion of the knee was greater for the DKV group (p=0.017). After core muscle fatigue, there was an increase in the angular excursion of the hip in the sagittal plane (p= 0.040) and an increase in the linear displacement of the shoulder in all directions (medium-lateral p<0.001; anteroposterior p<0.001 and vertical p=0.049) for both groups. The DKV group, in the preparatory phase, showed greater iEMG of the vastus lateralis (p=0.005) and, in the ascending phase in the posteromedial direction, greater iEMG of the tibialis anterior (p=0.001) when compared to the NDKV. After core muscle fatigue, both groups presented higher iEMG in the preparatory phase for the semitendinosus muscles (p=0.004), gluteus medius (p=0.009), gluteus maximus (p=0.016); while in the descending phase in the anterior direction there was lower iEMG for the tibialis anterior (p=0.006), medial gastrocnemius (p=0.039), semitendinosus (p=0.047) muscles, and higher iEMG for the gluteus medius (p=0.047); in the descending phase, in the posterolateral direction: lower iEMG for the tibialis anterior (p<0.001); in the posterolateral ascending phase, greater iEMG for the biceps femoris (p=0.014). CONCLUSION: In both functional tests, the runners in the DKV group presented different strategies to perform the SDT and YBT, in relation to those in the NDKV, and the immediate effect of core muscle fatigue was similar in those runners in the DKV and NDKV. In YBT there was an increase in joint range of motion in the lower limb. There was also a reduction in the EMG activity of the main muscles of the lower limb, but with greater displacement of the trunk, in all directions.