title: Influence of prolonged wearing of unstable shoes on upright standing postural control.
abstract: OBJECTIVE
  To study the influence of prolonged wearing of unstable shoes on standing postural control in prolonged standing workers.
  
  
  METHODS
  The participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8weeks. Stabilometry parameters related to centre of pressure (CoP), rambling (RM) and trembling (TR) as well as the total agonist/antagonist muscle activity, antagonist co-activation and reciprocal activation were evaluated during upright standing, before and after the 8weeks period. In both moments, the subjects were evaluated wearing the unstable shoes and in barefoot.
  
  
  RESULTS
  The unstable shoe condition presented increased CoP displacement related variables and decreased co-activation command compared to barefoot before and after the intervention. The prolonged wearing of unstable shoes led to: (1) reduction of medial-lateral CoP root mean square and area; (2) decreased anteroposterior RM displacement; (3) increased anteroposterior RM mean velocity and mediolateral RM displacement; (4) decreased anteroposterior TR RMS; and (5) increased thigh antagonist co-activation in the unstable shoe condition.
  
  
  CONCLUSIONS
  The unstable shoe condition is associated to a higher destabilising effect that leads to a selection of more efficient and accurate postural commands compared to barefoot. Prolonged wearing of unstable shoes provides increased effectiveness and performance of the postural control system, while wearing of unstable shoes in upright standing, that are reflected by changes in CoP related variables and by a reorganisation of postural control commands.
authors.affiliation: Escola Superior da Tecnologia de Saúde do Porto, Área Científica de Fisioterapia, Centro de Estudos de Movimento e Actividade Humana, Rua Valente Perfeito, 322 - 4400-330 Vila Nova de Gaia, Portugal; Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal. Electronic address: asp@estsp.ipp.pt.
authors.forename: Andreia S P
authors.initials: AS
authors.lastname: Sousa
authors.affiliation: Escola Superior da Tecnologia de Saúde do Porto, Área Científica de Fisioterapia, Centro de Estudos de Movimento e Actividade Humana, Rua Valente Perfeito, 322 - 4400-330 Vila Nova de Gaia, Portugal. Electronic address: rmacedo@estsp.ipp.pt.
authors.forename: Rui
authors.initials: R
authors.lastname: Macedo
authors.affiliation: Escola Superior da Tecnologia de Saúde do Porto, Área Científica de Física, Centro de Estudos de Movimento e Actividade Humana, Rua Valente Perfeito, 322 - 4400-330 Vila Nova de Gaia, Portugal. Electronic address: rss@estsp.ipp.pt.
authors.forename: Rubim
authors.initials: R
authors.lastname: Santos
authors.affiliation: Laboratório de Biomecânica do Porto, Faculdade de Desporto, Universidade do Porto, Porto, Portugal. Electronic address: filipas@fade.up.pt.
authors.forename: Filipa
authors.initials: F
authors.lastname: Sousa
authors.affiliation: Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal. Electronic address: andreiasilva88@gmail.com.
authors.forename: Andreia
authors.initials: A
authors.lastname: Silva
authors.affiliation: Instituto de Ciência e Inovação em Engenharia Mecânica e Engenharia Industrial, Departamento de Engenharia Mecânica, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal. Electronic address: tavares@fe.up.pt.
authors.forename: João Manuel R S
authors.initials: JM
authors.lastname: Tavares
mesh_terms: D000328:Adult; D004576:Electromyography; D006804:Ergonomics; D005260:Female; D006801:Humans; D008875:Middle Aged; D004856:Postural Balance; D011187:Posture; D012775:Shoes; D016474:Weight-Bearing; D055815:Young Adult
keywords: Antagonist co-activation; Postural control performance; Prolonged standing workers; Reciprocal activation; Stabilometry; Unstable support