title: The recruitment order of scapular muscles depends on the characteristics of the postural task.
abstract: Previous studies show that the scapular muscle recruitment order could possibly change according to the characteristics of the postural task. We aimed to compare the activation latencies of serratus anterior (SA), upper, middle, and lower trapezius (UT, MT and LT, respectively) between an unpredictable perturbation (sudden arm destabilization) and a predictable task (voluntary arm raise) and, to determine the differences in the muscle recruitment order in each task. The electromyographic signals of 23 participants were recorded while the tasks were performed. All scapular muscles showed earlier onset latency in the voluntary arm raise than in the sudden arm destabilization. No significant differences were observed in the muscle recruitment order for the sudden arm destabilization (p>0.05). Conversely, for voluntary arm raise the MT, LT SA and anterior deltoid (AD) were activated significantly earlier than the UT (p<0.001). Scapular muscles present a specific recruitment order during a predictable task: SA was activated prior to the AD and the UT after the AD, in a recruitment order of SA, AD, UT, MT, and LT. While in an unpredictable motor task, all muscles were activated after the destabilization without a specific recruitment order, but rather a simultaneous activation.
authors.affiliation: Laboratorio de Control Motor Humano, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile; Escuela de Kinesiología, Facultad de Salud, Universidad Santo Tomás, Chile. Electronic address: gmendez@utalca.cl.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Mendez-Rebolledo
authors.affiliation: Laboratorio de Control Motor Humano, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile.
authors.forename: Valeska
authors.initials: V
authors.lastname: Gatica-Rojas
authors.affiliation: University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, Potsdam, Germany.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Martinez-Valdes
authors.affiliation: ARC Centre of Excellence for Mathematical and Statistical Frontiers, Queensland University of Technology, Brisbane, Australia.
authors.forename: H B
authors.initials: HB
authors.lastname: Xie
mesh_terms: D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D011187:Posture; D011930:Reaction Time; D011999:Recruitment, Neurophysiological; D012540:Scapula / Q000294:innervation / Q000502:physiology*; D012782:Shoulder / Q000502:physiology; D012785:Shoulder Joint / Q000502:physiology
keywords: Anticipatory; Compensatory; Electromyography; Motor control; Muscle latency; Reaction time