Joint knee loads during squat with constant or variable resistance in males. A clinical trial.

BACKGROUND: In the squat movement, the use of constant resistance (CR) generates greater compression and shear forces close to 90° of knee flexion, increasing joint overload. However, when used variable resistance (VR) there is no consensus about the effect of knee joint load. The aim of this study was to compare knee torques using constant or variable resistance during the squat exercise. METHODS: Twenty-one healthy male subjects (mean age, 24 [SD, 3] years; height, 1.76 [SD, 0.04] m), who practice squats during strength training routine. Were simultaneously record data from the platform force and tridimensional kinematic to obtain torques around knee. 15 repetitions were performed up to maximum knee flexion with the use of variable (RV) or constant (CR) resistance in a single session. RESULTS: Significant differences regarding the angles only in the sagittal plane at the end of the ascending phase of the squat, with less knee extension in the VR condition. In the sagittal and frontal planes, lower values of extensor and abductor torque were found in the VR condition at the angles of greater knee flexion. CONCLUSION: The use of variable resistance compared to constant resistance seems to be an alternative to be considered when the objective is to minimize the internal loads on the knee joint in exercises such as the squat in amplitudes of greater flexion. This study indicated that VR helps subjects who are learning the squat movement, enabling the application of this knowledge in physical therapy or physical training clinics.

Center of pressure position in the touches of the star excursion balance test in healthy individuals.

BACKGROUND: The Star Excursion Balance Test (SEBT) is a clinical test that aims to assess postural control. Its interpretation is related to the understanding of the motor specificities required. Adjustments must be made to the center of pressure (COP) to maintain balance during testing movements. Comprehend the specifics of these adjustments for each direction can allow the development of more suitable exercises for balance training. The aim was to compare the positions of the COP on the different directions of the SEBT and correlate the reachs obtained in the SEBT with the distances from the COP to the borders of the base of support (BOS). METHODS: Sixteen healthy subjects participated in the study. Measurements were made by performing the SEBT over the force platform. The Kruskal-Wallis test followed by Bonferroni's post hoc test was used to compare directions. The Pearson correlation test was used to check the correlation of parametric variables and Spearman correlation test for the nonparametric ones. RESULTS: The position of the COP at the touch differs from the anterior direction to the other directions of the SEBT and the performance in this direction is correlated with the proximity of the COP to the anterior limit of the support base. The performances in the other directions did not correlate with the COP position. CONCLUSION: The requirements of the compensation mechanisms for postural control are different between the directions of the SEBT.