RESUMO
Chronic back tiredness or fatigue is a common complaint of people who have a history of osteoporotic vertebral fracture. Trunk muscle endurance has not been studied in people with vertebral osteoporosis, partly due to the lack of assessment tools. We developed a measure of combined trunk and arm endurance suitable for people with vertebral osteoporosis, timed loaded standing (TLS). TLS measures the time a person can stand while holding a two-pound dumbbell in each hand with the arms at 90 degrees of shoulder flexion and the elbows extended. Intraclass correlation coefficients (ICCs) for same day inter-trial and six to ten day test-retest reliability were 0.89 (lower bound 95% confidence interval [LB 95% CI] 0.79) and 0.84 (LB 95% CI 0.68), respectively, in a sample of 21 older women with no known osteoporosis. In 127 women with vertebral fractures, the ICC for same day inter-trial reliability was 0.81 (LB 95% CI 0.75). In a sub-sample of 30 of these women with vertebral fractures, the six to ten day test-retest reliability was 0.85 (LB 95% CI 0.75). Moderately strong and statistically significant (p < or = 0.05) correlations were found between TLS and sixteen of eighteen measures of physical impairment and function. Functional reach distance, gait velocity, MOS-36 Physical Function Subscale, shoulder flexion strength, and six minute walk distance were most strongly associated with TLS time. Women with vertebral fractures who endorsed having back tiredness when standing and working with the arms in front of the body, sitting to rest because of back tiredness or pain, and planning rest periods because of back tiredness or pain had significantly lower TLS times. TLS is a simple, safe physical performance measure of combined trunk and arm endurance that demonstrates acceptable reliability (inter-trial and test- retest) and concurrent validity.