Synergetic control of the vertical displacement of the foot during the swing phase of running: analysis using the uncontrolled manifold (UCM) approach

• Grant number: 21/10105-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2022
• End date: November 30, 2023
• Field of knowledge: Health Sciences - Physical Education
• Principal Investigator: Paulo Barbosa de Freitas Júnior
• Grantee: Mateus Santos Dias
• Host Institution: Pró-Reitoria de Pós-Graduação e Pesquisa. Universidade Cruzeiro do Sul (UNICSUL). São Paulo , SP, Brazil

Abstract

Controlling the vertical position of the foot during the swing phase is an important aspect of running. When the central nervous system (CNS) directly controls a certain performance variable (eg, horizontal or vertical displacement of the body's center of mass, COM), the variability of motor elements (e.g., joint angles) relevant to the control of this variable is greater than the variability of the performance variable itself (total variability of the motor elements >> variability of the performance variable). Uncontrolled manifold (UCM) analysis has been used to test whether the CNS directly controls a certain performance variable via the coordination and control of relevant motor elements. During walking it was observed that the variability (variance) of the mediolateral displacement of the foot is less than the sum of the total variability (variance) of the task-relevant motor elements (i.e., segmental angles). This happens because part of the variance of the elements does not affect the performance variable, which is being controlled. The variance that does not affect task performance (called VUCM or good variability) is important to ensure system flexibility against possible disturbances that may occur while walking (e.g., the appearance of an unexpected obstacle). Another part of the variance of the motor elements interferes with the task performance, generating some instability in the performance variable; hence it is called bad variance or variance orthogonal to the UCM (VORT). The relationship between these two variances is defined as the synergy index (”V). In the present project, we will evaluate how the motor elements (i.e., joint angles) vary trial by trial to ensure the stability of the vertical foot displacement of inexperienced runners during treadmill running at different speeds. We will measure the good and bad variances and the synergy index (V, difference between VUCM and VORT) to confirm that the CNS stabilizes the vertical displacement of the foot during the swing phase, directly controlling the angles of the joints relevant to this task. This will be confirmed if VUCM>VORT and V>0. To achieve this goal, we will use kinematic data from running on a treadmill from 28 adults (27 men and 1 woman) between 22 and 51 years of age, already collected and made available in open running databases1. Kinematic data from markers positioned in specific places on the body will be used to calculate the linear and angular displacements of segments and joints, respectively. Kinetic data will be used to determine the start and end of each race cycle and its phases. Using these data we will calculate the UCM, VUCM, and VORT variables and the synergy index.(AU).