Lluc Montull, Institut Nacional d'Educacio Fisica de Catalunya (INEFC), Universitat de Barcelona, Spain
Pedro Passos, CIPER, Universidade de Lisboa. Portugal
Lluis Rocas, Institut Nacional d'Educacio Fisica de Catalunya (INEFC), Universitat de Barcelona, Spain
Joao Milho, Instituto Politecnico de Lisboa and IDMEC, Universidade de Lisboa, Portugal
Natalia Balague, Institut Nacional d'Educacio Fisica de Catalunya (INEFC), Universitat de Barcelona, Spain

Abstract: Proprioceptive based interpersonal communication, playing a crucial role in cooperative motor tasks, needs further investigation. This study aimed to explore the interpersonal coordination of dyads cooperating to stand up in balance on a slackline through the study of inter and intrapersonal synergies. With this purpose, acceleration time series of the slackline as well as of both legs and the center of mass of slackliners were recorded. The Uncontrolled Manifold was used to evaluate inter and intrapersonal synergies, and afterwards, the Hierarchical Cluster Analysis was performed to detect hypothetical embedded organization of synergies. Furthermore, the kinematic variability of the synergetic elements was studied through the Detrended Fluctuation Analysis to find potential stabilizing roles among slackliners. Inter and intrapersonal synergies were identified with a higher hierarchical dominance of the former. Interpersonal stabilizing roles were demonstrated among slackliners, revealing greater kinematic control of free leg and the center of mass in those slackliners with more training experience and higher task performance. This exploratory study of interpersonal coordination found that there was an embedded organization between inter and intrapersonal synergies in which stabilizing roles emerged. Dyads established a dominantly proprioceptive dialogue to form a co-adaptive whole and cope with an unstable environment.

Keywords: nonverbal communication, multilevel coordination, embedded organization, kinematic variability, stabilizing roles