Time loaded standing: A measure of combined trunk and arm endurance suitable for people with vertebral osteoporosis

Chronic back tiredness or fatigue is a common complaint of people who have a history of osteoporotic vertebral fracture. Trunk muscle endurance has no t been studied in people with vertebral osteoporosis, partly due to the lac k of assessment tools. We developed a measure of combined trunk and arm end urance suitable for people with vertebral osteoporosis, timed loaded standi ng (TLS). TLS measures the time a person can stand while holding a two-poun d dumbbell in each hand with the arms at 90 degrees of shoulder flexion and the elbows extended. Intraclass correlation coefficients (ICCs) for same d ay 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 reliab ility 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 (L B 95% CI 0.75). Moderately: strong and statistically significant (p less th an or equal to 0.05) correlations were found between TLS and sixteen of eig hteen measures of physical impairment and function. Functional reach distan ce, gait velocity, MOS-36 Physical Function Subscale, shoulder flexion stre ngth, and six minute walk distance were most strongly associated with TLS t ime. Women with vertebral fractures who endorsed having back tiredness when standing and working with the arms in front of the body, sitting to rest b ecause 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 demo nstrates acceptable reliability (inter-trial and test- retest) and concurre nt validity.