Platform & Poster Presentations Csm 2006: Platform Presentations
Purpose/Hypothesis: After hip fracture, elders have decreased lower extremity (LE) strength on the fractured side both acutely and 18 months later. Elders with hip fractures are likely to fall again and LE weakness is associated with the highest relative risk for future falls. Peak isometric force is commonly reported to characterize muscle performance; however, the ability to generate force quickly has been implicated as important to avoid falling. The rate of force development (RFD) and the impulse (integrated area under the force time curve) may, therefore, be important characteristics to examine in a group of elders known to be at risk of future falls. The purpose of this study was to describe the force/time characteristics of the quadriceps muscles in elders after hip fracture and to compare these characteristics in the injured and non‐injured LE. Number of Subjects: Subjects were recruited as part of an ongoing exercise trial. Twenty‐one subjects (4 men, 17 women) ranging in age from 68 to 91 years (mean = 80) participated in this study. On average, subjects were 6 months post‐fracture, had a BMI of 27.4 kg/m2, 4 co‐morbidities, and a Mini Mental State Exam score of 28. Materials/Methods: Subjects performed 4 sec maximal isometric extension contractions on the Kincom dynamometer at 70° of knee flexion. Subjects were instructed to “push as hard and fast” as possible for at least 3 trials, 2 of which had to be within 10% of each other to be considered valid. Peak torque (Nm), RFD (slope of the force time curve) and impulse (the area under the curve) from 0‐100 ms and 0‐200 ms were the obtained. Results: Means and standard deviations are listed first for the involved side and then for the uninvolved side. Peak torque (Nm) 72.6plus or minus 26.7 128.0 plus or minus 44.2 RFD at 100 msec (Nm/sec) 165plus or minus 162 267 plus or minus 239 RFD at 200 msec (Nm/sec) 168 plus or minus 128 312 plus or minus 156 Impulse at 100 msec(Nm*sec) 0.75plus or minus .78 1.30 plus or minus 1.35 Impulse at 200 msec(NM*sec) 3.57plus or minus 2.97 6.10plus or minus 3.91 Conclusions: Six months after hip fracture, mean peak torque, rate of force development and impulse were decreased when comparing the injured side to the uninjured side. Although peak isometric torque values are comparable to frail elders, RFD and impulse are greatly decreased in elders post hip fracture compared to values reported for elders awaiting elective joint replacement. Clinical Relevance: Peak torque, rate of force development and impulse may be important aspects to consider when designing fall prevention exercise programs for elders after hip fracture.