Relação entre a disparidade de força entre membros inferiores e estabilidade postural em atletas de voleibol

Volleyball is a sport in which the laterality dominant limb shows superior strength and coordination because of its preferential use. Asymmetrical tendencies during the landing after the jump when striking or blocking actions are predominant for most part of game (ARRUDA; EDUARDO, 2008). Adaptations include imbalance of forces in static and dynamic motions at the knee joint, which increases risk for injury. Also, asymmetries in balance control during jumping and landing associate with a general postural instability that can be observed during static balance tasks. The purpose of this study was to investigate relationship between unequal lower limb strength (muscle imbalance) and postural stability levels in volleyball athletes and non-athletes. Nine female volleyball athletes and 10 active non-athletes participated in this study. Four encouters with participants were scheduled: three encounters in the bodybuilding gymnasium to collect anthropometric measures (weight, height for BMI, thigh circumference, which provided an initial diagnosis about asymmetry), and to perform the isometric strength test (i.e., leg press using a load cell and a force transducer to calculate uni an bilateral strength). The last encounter was in the laboratory where a balance test on a force platform was administered under five test conditions, with three repetitions each: baseline (natural standing position), one-leg standing, right side, with full vision (D_CV), and blindfolded (D_SV), one-leg standing, left side, with full vision (E_CV), and blindfolded (E_SV). The stability levels were evaluated using the path length parameters which was based on the total displacement of the center of pressure (DTCP). . Both groups shows asymmetric strength levels between legs, with better performance for the right leg. An ANOVA three way using the DTCP for the CV condition, legs (D x E), trials (3) with repeated measures for the first two factors and with a between (three)...

Magnetic Field Line Escape: Comparison with Mean Free Path

In the present work, we determine the fraction of magnetic field lines that reach the tokamak wall leaving the plasma surrounded by a chaotic layer created by resonant perturbations at the plasma edge. The chaotic layer arises in a scenario where an integrable magnetic field with reversed magnetic shear is perturbed by an ergodic magnetic limiter. For each considered line, we calculate its connection length, i.e. the number of toroidal turns that the field lines complete before reaching the wall. We represent the results in the poloidal section in which the initial coordinates are chosen. We also estimate the radial profile of the fraction of field lines, for different temperatures, whose connection lengths are smaller than the electron collisional mean free path.