title: Carrying a rifle with both hands affects upper body transverse plane kinematics and pelvis-trunk coordination.
abstract: The purpose of this study was to assess how carrying a rifle in both hands affects upper body motion and coordination during locomotion. In total, 11 male soldiers walked (1.34 m/s) and ran (2.46 m/s) with a weapon (M4 condition) and without a weapon (NW condition) while kinematic pelvis and trunk data were collected. Two-way ANOVA was used to compare segmental ranges of motion (ROM), pelvis-trunk coordination (continuous relative phase) and coordination variability between gait mode and weapon combinations. Carrying a weapon decreased sagittal plane trunk ROM at both speeds and increased trunk rotation during running. Mean (±SD) transverse plane coordination was more in-phase while carrying a weapon (M4 = 83°±31, NW = 60°±36, p = 0.027) and transverse plane coordination variability decreased (M4 = 23°±3.6, NW = 15°±4.4, p = 0.043). Coordination differences between M4 and NW were similar to differences reported in the literature between individuals with and without back pain. Long-term injury implications due to decreased coordination variability are discussed. STATEMENT OF RELEVANCE: Knowledge of the effects of rifle carriage on pelvis-trunk coordination may provide insight into short-term protective strategies and long-term injury mechanisms. These should be considered in occupations requiring individuals to carry torso loads in combination with holding an object in both hands that restricts arm swing.
authors.affiliation: Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA, USA. joseph.seay@us.army.mil
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Seay
authors.forename: Leif
authors.initials: L
authors.lastname: Hasselquist
authors.forename: Carolyn K
authors.initials: CK
authors.lastname: Bensel
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005389:Firearms; D006801:Humans; D017770:Lifting; D008124:Locomotion / Q000502:physiology; D008297:Male; D008889:Military Personnel; D009068:Movement / Q000502:physiology; D016273:Occupational Exposure / Q000517:prevention & control; D010388:Pelvis / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular; D012420:Running / Q000502:physiology*; D014481:United States; D034941:Upper Extremity / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult