Hypogravity reduces trunk admittance and lumbar muscle activation in response to external perturbations

Enrico De Martino, Sauro E. Salomoni, Andrew Winnard, Kristofor McCarty, Kirsty Lindsay, Sherveen Riazati, Tobias Weber, Jonathan Scott, David A. Green, Julie Hides, Dorothée Debuse, Paul W. Hodges, Jaap H. van Dieën, Nick Caplan

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Reduced paraspinal muscle size and flattening of spinal curvatures have been documented after spaceflight. Assessment of trunk adaptations to hypogravity can contribute to development of specific countermeasures. In this study, parabolic flights were used to investigate spinal curvature and muscle responses to hypogravity. Data from five trials at 0.25 g, 0.50 g, and 0.75 g were recorded from six participants positioned in a kneeling-seated position. During the first two trials, participants maintained a normal, upright posture. In the last three trials, small-amplitude perturbations were delivered in the anterior direction at the T10 level. Spinal curvature was estimated with motion capture cameras. Trunk displacement and contact force between the actuator and participant were recorded. Muscle activity responses were collected by intramuscular electromyography (iEMG) of the deep and superficial lumbar multifidus, iliocostalis lumborum, longissimus thoracis, quadratus lumborum, transversus abdominis, obliquus internus, and obliquus externus muscles. The root mean square iEMG and the average spinal angles were calculated. Trunk admittance and muscle responses to perturbations were calculated as closed-loop frequency-response functions. Compared with 0.75 g, 0.25 g resulted in lower activation of the longissimus thoracis (P = 0.002); lower responses of the superficial multifidus at low frequencies (P = 0.043); lower responses of the superficial multifidus (P = 0.029) and iliocostalis lumborum (P = 0.043); lower trunk admittance (P = 0.037) at intermediate frequencies; and stronger responses of the transversus abdominis at higher frequencies (P = 0.032). These findings indicate that exposure to hypogravity reduces trunk admittance, partially compensated by weaker stabilizing contributions of the paraspinal muscles and coinciding with an apparent increase of deep abdominal muscle activity.NEW & NOTEWORTHY This study presents for the first time novel insights into the adaptations to hypogravity of spinal curvatures, trunk stiffness, and paraspinal muscle activity. We showed that exposure to hypogravity reduces the displacement of the trunk by an applied perturbation, partially compensated by weaker stabilizing contributions of the paraspinal muscles and concomitant increase in abdominal muscle responses. These findings may have relevance for future recommendations for planetary surface explorations.

Original languageEnglish
Pages (from-to)1044-1055
Number of pages12
JournalJournal of applied physiology (Bethesda, Md. : 1985)
Volume128
Issue number4
Early online date13 Apr 2020
DOIs
Publication statusPublished - Apr 2020

Keywords

  • intramuscular electromyography
  • low gravity
  • lumbar spine
  • parabolic flight
  • trunk stabilization

Fingerprint Dive into the research topics of 'Hypogravity reduces trunk admittance and lumbar muscle activation in response to external perturbations'. Together they form a unique fingerprint.

Cite this