Some studies have shown a relationship between trunk muscle strength and low back pain. Measures of trunk muscle strength and endurance, which are feasible in the clinical setting, are needed. The purpose of this study was to determine interrater reliability of 6 tests of abdominal and trunk extensor muscle strength and endurance. The tests included abdominal and extensor dynamic endurance, hand-held dynamometry of isometric flexion and extension, and abdominal and extensor static endurance. Thirty-nine healthy workers were recruited as subjects. Each was tested by 3 raters on 3 days within 1 week. Intraclass correlation coefficients (ICC) and the standard error of measurement (SEM) were calculated: abdominal dynamic endurance ICC = .89, SEM = 8 repetitions; extensor dynamic endurance ICC = .78, SEM = 9 repetitions; abdominal isometric force ICC = .25, SEM = 60 N; extensor isometric force ICC = .24, SEM = 68 N; abdominal static endurance ICC = .51, SEM = 35 seconds; extensor static endurance ICC = .59, SEM = 20 seconds. The dynamic endurance tests had acceptable interrater reliability. For the others, reliability was poor and the SEMs were large.

J Orthop Sports Phys Ther. 1997;26(4):200-208.

Key Words: muscle strength, assessment, low back

The assessment of muscle strength is a task performed frequently by physical therapists. The purposes of this study were to determine whether intrasession test-retest reliability differs between make and break tests and strength tests that do not require an assessor (eg, isometric Kin-Com test) and hand-held dynamometer (HHD) assessments. The elbow flexor strength of 32 healthy, female volunteers was measured under 4 test conditions: Kin-Com make and break, and HHD make and break. Two measurements were performed for each test condition by the same rater. The results showed: 1) measurements obtained using the HHD deviated from a normal distribution, 2) comparable reliability coefficients for the make and break tests were obtained from the Kin-Com device, 3) there was a higher reliability coefficient for the make test compared with the break test for the HHD tests, and 4) the measured forces for the break tests were higher than the make tests. The results support the premise that hand-held dynamometry is a viable alternative to more costly modes of isometric strength measurements, provided the assessor's strength is greater than that of the specific muscle group being measured.

J Orthop Sports Phys Ther. 1994;19(1):28-32.

Key Words: muscle strength, measurement, methods