​Efeitos da manipulação da superfície de apoio sobre a potência muscular de jovens hígidos durante a transição do sentado para de pé

Abstract

The transition from a seated to a standing position is one of the most frequently performed motor tasks in daily life, despite posing a biomechanical challenge. Given the importance of somatosensory feedback for postural control and the functional significance of the sit-to-stand transition, this study aimed to evaluate the effects of manipulating the support surface on the muscle power of healthy young adults during this transition. This was an observational, descriptive, quantitative, cross-sectional study. The final sample consisted of 15 healthy young adults with a mean age of 24 ± 2.35 years. Participants performed the sit-to-stand task under two experimental support surface conditions: stable (feet directly on the force platform) and unstable (using foam placed over the equipment). Each condition was performed at two distinct speeds: comfortable (VC) and accelerated (VA). Kinetic data were captured using a Wii Balance Board connected to the Brain Blox software. Routines generated in MATLAB were used to extract the variables of interest: peak muscle power, peak vertical ground reaction force (GRF), and velocity during the rising phase of the sit-to-stand transition. Statistical analysis was performed using repeated-measures analysis of variance. The results revealed that GRF and rising velocity showed a main effect only for the speed factor, with higher values ​observed when the task was performed at VA, regardless of the surface. The support surface, in turn, influenced muscle power generation only when the sit-to-stand transition was performed at VA. Based on these results, it is concluded that manipulating the support surface reduces muscle power in healthy young adults during the sit-to-stand transition only when the task is performed at an accelerated speed.