The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access published online on October 27, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, doi:10.1093/gerona/glp153
Age Differences in Energy Absorption in the Upper Extremity During a Descent Movement: Implications for Arresting a Fall
Injury Prevention and Mobility Lab, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
Address correspondence to Stephen N. Robinovitch, PhD, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6. Email: stever{at}sfu.ca
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Abstract |
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Background: Falls are the number one cause of unintentional injury in older adults. The protective response of "breaking the fall" with the outstretched hand is often essential for avoiding injury to the hip and head. In this study, we compared the ability of young and older women to absorb the impact energy of a fall in the outstretched arms.
Methods: Twenty young (mean age = 21 years) and 20 older (M = 78 years) women were instructed to slowly lower their body weight, similar to the descent phase of a push-up, from body lean angles ranging from 15° to 90°. Measures were acquired of peak upper extremity energy absorption, arm deflection, and hand contact force.
Results: On average, older women were able to absorb 45% less energy in the dominant arm than young women (1.7 ± 0.5% vs 3.1 ± 0.4% of their body weight x body height; p < .001). These results suggest that, even when both arms participate equally, the average energy content of a forward fall exceeds by 5-fold the average energy that our older participants could absorb and exceeds by 2.7-fold the average energy that young participants could absorb.
Conclusions: During a descent movement that simulates fall arrest, the energy-absorbing capacity of the upper extremities in older women is nearly half that of young women. Absorbing the full energy of a fall in the upper extremities is a challenging task even for healthy young women. Strengthening of upper extremity muscles should enhance this ability and presumably reduce the risk for injury to the hip and head during a fall.
Keywords Hip fracture; Wrist fracture; Falls; Biomechanics; Aging
Received: October 23, 2008; Accepted: September 16, 2009