Journal of rehabilitation medicine 48(10) 893-902 doi 10.2340/16501977-2164
To investigate the short- and long-term reliability of isometric trunk strength measurements in patients with chronic low back pain in different age groups.
Test-retest reliability study.
A total of 210 patients (age groups 18-39, 40-59 and 60-90 years).
Patients performed testing at baseline, 1-2 days (day 2) and 6 weeks.
Only the oldest age group showed similar extension strength on all three test days All age groups showed significant changes in rotation and flexion scores from baseline to 6 weeks. Younger age groups (18-39 and 40-59 years) showed significant increases in extension, flexion, and rotation strength at both short-term (baseline to day 2) and long-term (baseline to 6 weeks) retests, but not from day 2 to 6 weeks. In patients over 60 years of age the smallest real differences normalized to baseline (%) were smaller from day 2 to 6 weeks than from baseline to 6 weeks. Long-term intraclass correlation coefficients were lowest between baseline and 6 weeks. No relevant impacts of feelings, motivation, or pain on reliability were detected.
Reliability of isometric trunk strength measurements in patients with chronic low back pain is similar in older and younger patients. Short-term test repetition a few days after baseline is recommended, if clinically feasible, and especially in research evaluating the effects of exercise on strength.