Active responses decrease impact forces at the hip and shoulder in falls to the side

Active responses, such as using the arm to break the fall, may be an effect ive means of decreasing likelihood of injury in a fall and may help explain why only a small percentage of falls result in a fracture. We quantified t he impact force at the hip and shoulder in falls to the side from a kneelin g position under three conditions: (1) attempting to break the fall by usin g an arm, (2) falling with the body relaxed; and (3) falling with the body tensed. Subjects fell from a kneeling position onto a force platform array covered with foam padding and impact force data were recorded. The ground r eaction force-time curve was generally bimodal due to sequential impacts of the hip and shoulder. Impact forces at the hip and shoulder were 12 and 16 % less for the slap condition (p < 0.05) than for the tensed condition. The impact forces for the relaxed and tensed conditions were not significantly different, although impact forces tended to be less in the relaxed conditi on. We concluded that active responses reduce the impact forces experienced at the hip and shoulder in falls to the side. Decreased effectiveness of p rotective responses, due to increases in reaction time and decreases in str ength with age, may help explain why so many hip fractures occur in the eld erly but so few occur in younger people. (C) 1999 Elsevier Science Ltd. All rights reserved.