Kyu-Jung Kim1, James A Ashton-Miller. 1. Department of Mechanical Engineering, University of Wisconsin--Milwaukee, 3200 N Cramer Street, 1239 EMS, Milwaukee, WI 53211, USA. kimk2@uwm.edu
Abstract
OBJECTIVE: This study tried to isolate critical biomechanical factors in fall arrests using the upper extremity during simulated forward falls. This study also attempted to find the differences in those factors between young and old age groups. BACKGROUND: The role of the upper extremity is not well defined despite its primary usage as a local shock absorber during fall impact. DESIGN: Comparative study in which two age groups underwent motion analysis.Methods. Ten healthy older males (mean age, 66.4 years) and 10 young males (mean age, 24.1 years) volunteered to perform self-initiated and cable-released falls at selected falling distances, while the joint motion and impact forces at the hand were recorded. RESULTS: Significant age differences were demonstrated in joint kinematics and impact force parameters at close distances. Excessive reflexive responses of the upper extremity in cable-released falls for the older adults resulted in 10-15 times higher peak impact forces and 2-3 times shorter body braking time than in self-initiated falls. CONCLUSIONS: Pre-impact activities of the upper extremity predispose the post-impact response during fall arrests. Suppressing excessive pre-impact reflexive activation of the arms could efficiently decrease the risk of fall-related injuries, which calls for securing sufficient arm movement time. Any fall prevention strategy that can increase arm movement time would be effective against injuries of the upper extremity during falling in the older adults. RELEVANCE: The findings will help to understand underlying mechanisms of fall arrest using the upper extremity for prevention of fall-related fractures.
OBJECTIVE: This study tried to isolate critical biomechanical factors in fall arrests using the upper extremity during simulated forward falls. This study also attempted to find the differences in those factors between young and old age groups. BACKGROUND: The role of the upper extremity is not well defined despite its primary usage as a local shock absorber during fall impact. DESIGN: Comparative study in which two age groups underwent motion analysis.Methods. Ten healthy older males (mean age, 66.4 years) and 10 young males (mean age, 24.1 years) volunteered to perform self-initiated and cable-released falls at selected falling distances, while the joint motion and impact forces at the hand were recorded. RESULTS: Significant age differences were demonstrated in joint kinematics and impact force parameters at close distances. Excessive reflexive responses of the upper extremity in cable-released falls for the older adults resulted in 10-15 times higher peak impact forces and 2-3 times shorter body braking time than in self-initiated falls. CONCLUSIONS: Pre-impact activities of the upper extremity predispose the post-impact response during fall arrests. Suppressing excessive pre-impact reflexive activation of the arms could efficiently decrease the risk of fall-related injuries, which calls for securing sufficient arm movement time. Any fall prevention strategy that can increase arm movement time would be effective against injuries of the upper extremity during falling in the older adults. RELEVANCE: The findings will help to understand underlying mechanisms of fall arrest using the upper extremity for prevention of fall-related fractures.