Os efeitos da fadiga nos membros inferiores em indivíduos com diferentes níveis de assimetria de força

Abstract

Understanding the kinetics of lower limb fatigue induced by successive countermovement jump (CMJ), and whether this effect is common among groups with different levels of strength asymmetry can provide important subsidies for sports training. The aim of this study was to contribute to a better understanding of fatigue´s kinetics in lower limbs, separately and in asymmetry, in dynamic and kinematic parameters of CMJ and skin temperature. Twenty-seven male subjects participated in the study. All subjects performed five CMJ before and after (immediately, 24 h and 48 h) the accomplishment of a fatigue protocol. Dynamic variables (peak force, time to reach peak force, peak impact, time to reach peak impact, peak power, rate of force development, total impulse, positive impulse and negative impulse), and kinematics variables of the knee, ankle and hip joints (angular displacement, peak extension velocity, peak flexion velocity, angular momentum and peak angular power) extracted from the CMJ, and skin temperature, were measured for both limbs, and were used to calculate the lower limb asymmetry. Fatigue was induced by performing a 100 CMJ protocol, divided into five sets of 20 trials with a 30 s interval between sets. To verify if subjects were in a fatigued state the following variables were collected: jump height, heart rate and perceived exertion rate. In order to verify fatigue´s kinetics, muscle damage and its subsequent inflammatory process were evaluated by the following variables: creatine kinase blood concentration ([CK]) and mean temperature of the skin of both lower limbs. All measures were performed before, immediately, 24 h and 48 h after the fatigue protocol. Comparisons of dynamic and kinematics variables were performed between lower limbs, groups (more or less asymmetrical) and moments (immediately, 24 h and 48 h after), and between groups and moments for asymmetry. When comparing both lower limbs, only peak power, total and positive impulse, rate of force development, knee peak flexion velocity, ankle angle displacement and peak plantar flexion velocity showed relevant results for the purpose of this study (p < 0,5). The other variables had only moment main effect (p < 0,5) or did not present any significant result. Regarding asymmetry, only hip displacement showed significant interaction (p < 0,5), and only peak power and impulse showed group main effect (p < 0,5). From the results of the present study is possible to conclude that peak power and total impulse seem to be the most sensible variables to evaluate the effects of fatigue in lower limbs and in asymmetry levels. And that both lower limbs and groups (more or less asymmetrical) behave differently after performing a fatigue protocol with CMJ.