title: Use of a backpack alters gait initiation of high school students.
abstract: We assessed how backpack carriage influences the gait initiation (GI) process in high school students, who extensively use backpacks. GI involves different dynamics from gait itself, while the excessive use of backpacks can result in adverse effects. 117 high school students were evaluated in three experimental conditions: no backpack (NB), bilateral backpack (BB), and unilateral backpack (UB). Two force plates were used to acquire ground reaction forces (GRFs) and moments for each foot separately. Center of pressure (COP) scalar variables were extracted, and statistical parametric mapping analysis was performed over the entire COP/GRFs time series. GI anticipatory postural adjustments (APAs) were reduced and were faster in backpack conditions; medial-lateral COP excursion was smaller in this phase. The uneven distribution of the extra load in the UB condition led to a larger medial-lateral COP shift in the support-foot unloading phase, with a corresponding vertical GRF change that suggests a more pronounced unloading swing foot/loading support foot mechanism. The anterior-posterior GRFs were altered, but the COP was not. A possible explanation for these results may be the forward trunk lean and the center of mass proximity of the base of support boundary, which induced smaller and faster APA, increased swing foot/support foot weight transfer, and increased load transfer to the first step.
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Goiânia, Goiás, Brazil. Electronic address: marcus@ufg.br.
authors.forename: Marcus Fraga
authors.initials: MF
authors.lastname: Vieira
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.
authors.forename: Georgia Cristina
authors.initials: GC
authors.lastname: Lehnen
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.
authors.forename: Matias
authors.initials: M
authors.lastname: Noll
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.
authors.forename: Fábio Barbosa
authors.initials: FB
authors.lastname: Rodrigues
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.
authors.forename: Ivan Silveira
authors.initials: IS
authors.lastname: de Avelar
authors.affiliation: Physical Education Department, Universidade Federal de São Carlos, São Carlos, Brazil.
authors.forename: Paula Hentschel Lobo
authors.initials: PH
authors.lastname: da Costa
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D002648:Child; D005260:Female; D005528:Foot / Q000502:physiology; D005684:Gait; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D011312:Pressure; D013334:Students; D016474:Weight-Bearing
keywords: Anticipatory postural adjustments; Backpack; Center of pressure; Gait initiation; Statistical parametric mapping