title: Biomechanical factors affecting the peak hand reaction force during the bimanual arrest of a moving mass.
abstract: Fall-related wrist fractures are among the most common fractures at any age. In order to learn more about the biomechanical factors influencing the impact response of the upper extremities, we studied peak hand reaction force during the bimanual arrest of a 3.4 kg ballistic pendulum moving toward the subject in the sagittal plane at shoulder height. Twenty healthy young and 20 older adults, with equal gender representation, arrested the pendulum after impact at one of three initial speeds: 1.8, 2.3, or 3.0 m/sec. Subjects were asked to employ one of three initial elbow angles: 130, 150, or 170 deg. An analysis of variance showed that hand impact force decreased significantly as impact velocity decreased (50 percent/m/s) and as elbow angle decreased (0.9 percent/degree). A two segment sagittally-symmetric biomechanical model demonstrated that two additional factors affected impact forces: hand-impactor surface stiffness and damping properties, and arm segment mass. We conclude that hand impact force can be reduced by more than 40 percent by decreasing the amount of initial elbow extension and by decreasing the velocity of the hands and arms relative to the impacting surface.
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor 48109, USA. degoedek@etown.edu
authors.forename: Kurt M
authors.initials: KM
authors.lastname: DeGoede
authors.forename: James A
authors.initials: JA
authors.lastname: Ashton-Miller
authors.forename: Albert B
authors.initials: AB
authors.lastname: Schultz
authors.forename: Neil B
authors.initials: NB
authors.lastname: Alexander
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control; D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D000886:Anthropometry; D001132:Arm / Q000502:physiology*; D001783:Blood Flow Velocity; D003198:Computer Simulation; D004548:Elasticity; D004551:Elbow Joint / Q000502:physiology*; D005260:Female; D050723:Fractures, Bone / Q000517:prevention & control*; D006225:Hand / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D009068:Movement; D012680:Sensitivity and Specificity; D012737:Sex Factors; D014783:Viscosity; D014954:Wrist Injuries / Q000503:physiopathology; D014955:Wrist Joint / Q000502:physiology