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Adaptive locomotion control in young adults during the tasks of alternate foot placement and step on target

Grant number: 16/02202-8
Support type:Scholarships in Brazil - Master
Effective date (Start): December 01, 2016
Effective date (End): February 28, 2018
Field of knowledge:Health Sciences - Physical Education
Principal Investigator:Renato de Moraes
Grantee:Andréia Abud da Silva Costa
Home Institution: Escola de Educação Física e Esporte de Ribeirão Preto (EEFERP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil


During locomotion in daily activities, we respond to environmental and task changes by adjusting the length and width of our steps. For this purpose, anticipatory, predictive and reactive control strategies are used, composing the adaptive locomotion. The adaptive locomotion control allows the necessary adjustments to begin at a certain distance in the tasks such as obstacle avoidance, stepping on a target or avoiding stepping on an undesirable area. The choice of these adjustments considers several factors, such as the displacement of the foot, the stability, the maintenance of forward progression and the information obtained from the various sensory systems. Unpredictable changes in the environment or in the task require corrections on different variables, including the trajectory of the foot. In this context, the tasks of stepping on a moving target and avoid stepping on an undesirable area, that has its location changed, are different in relation to latency and, consequently, in the pathways involved. The task of stepping on a target presents lower latency, which suggests the participation of subcortical pathways, while the task of avoiding stepping on an undesirable area shows higher values of latency, and thus, the involvement of cortical pathways. In this way, the insertion of a secondary concomitant cognitive task may influence more the task of avoiding stepping on an undesirable area than the task of stepping on a target. Thus, the goal of this study is to analyze the motor responses and the latencies to program the necessary adjustments in the tasks of stepping on a target and avoid stepping on an undesirable area, with and without a secondary concomitant cognitive task. It is expected that the addition of a cognitive task will affect more the latency of the locomotor task of avoiding stepping on an undesirable area than the task of stepping on a target, since the first task seems to be more dependent on cortical pathways. Twenty young, healthy adults (males and females) will be invited to participate in this study. Participants will walk in a 7 m long pathway, with a rectangle of 30 cm long x 15 cm wide projected on the ground to be stepped on or avoided, depending on the block of trials. In the step immediately before the rectangle, the participant will step on a force plate, which signal will be used to change or not the location where the target/obstacle will be projected. The rectangle can be moved forward, backward, laterally or medially, in both blocks. For the block of stepping on the target, the target will shift from the center (site of normal foot landing) to the periphery and the participant will be instructed to stepped on the target. For the obstacle avoidance block (i.e., alternate foot placement), the instruction will be is to avoid stepping the obstacle. In this block, the rectangle will be shifted from the periphery to the center. In both blocks there will be trials in which the rectangle does not have its location changed, taken as control trials. Moreover, in half of the trials of each condition within each block, participants will perform a cognitive task (monitoring digit test). In this test, the participant must count how many times a number, previously listened to, will be spoken during the audio recording that they listen to while perform the walking task. Ten retroreflective passive markers will be positioned bilaterally in the first metatarsal, fifth metatarsal, lateral malleolus and calcaneus (lateral and medial sides). The displacement of these markers will be tracked by cameras of the Vicon motion capture system. It will be calculated the success rate, percentage of adjustment, latency and distance travelled by the foot. The data of the first two variables will be analyzed by non-parametric statistical tests, while for the other variables it will be used analysis of variance. The significance level will be 0.05.

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DA SILVA COSTA, ANDREIA ABUD; DOS SANTOS, LUCIANA OLIVEIRA; MORAES, RENATO. Effect of a cognitive task on online adjustments when avoiding stepping on an obstacle and stepping on a target during walking in young adults. Experimental Brain Research, v. 236, n. 8, p. 2387-2397, AUG 2018. Web of Science Citations: 2.

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