Subject variability of shoulder abduction strength testing

Abstract

To quantify normal biological variability of shoulder abduction strength testing with an isokinetic and a hand-held dynamometer, we tested nine healthy subjects over a clinically relevant period. One side was tested with a Cybex at 60 deg/sec and the other with a hand-held dynamometer. Six maximal trials, following warmup, were conducted on each of 5 days, separated by 1 to 2 weeks. Intraday correlations of individual trials ranged from 0.82 to 0.995 for hand-held dynamometer, and 0.88 to 0.996 for Cybex. Interday correlations ranged from 0.94 to 0.98 for hand-held dynamometer, and 0.88 to 0.97 for Cybex. The best values to use for Cybex interday variability were the average of the first three repetitions, and yielded standard errors of 8.6% to 19.2% of the sample mean. The average of the last three repetitions were the best for hand-held dynamometers, and yielded standard errors of 5.5% to 10.8%. There was a significant decline (P less than 0.05) in strength of the mean of the last three versus the mean of the first three daily repetitions on Day 1 and 4 for hand-held dynamometers, and a trend toward this on the other days, that was not seen with Cybex. Regression of average Day 1 values for Cybex and hand-held dynamometer yielded r = 0.86 (P less than 0.01) with a slope of 1.07 indicating good agreement between modalities. In conclusion, intraday/interday correlations were high for Cybex and hand-held dynamometer. Interday variability was minimized by using the mean score of the first three and last three repetitions for Cybex and hand-held dynamometer, respectively. Changes in Cybex and hand-held dynamometer strength of less than 19% and 11%, respectively, are within the area of "measurement error" and should therefore not be considered clinically significant.

The Effect of Rotator Cuff Tear Size on Shoulder Strength and Range of Motion

“…For strength measures, the percent deficits were computed ([noninvolved -involved/noninvolved] × 100). Goniometric range of motion 20 and handheld dynamometry strength tests 19 have been shown to have good reliability in the upper extremity.…”

“…Handheld dynamometry has been shown to have similar reproducibility to isokinetic testing for shoulder abduction strength. 19 The purpose of this study was to determine to what extent rotator cuff tear size affects shoulder strength (assessed using a handheld dynamometer) and shoulder ROM.…”

Intraobserver and interobserver reliability for the strength test in the Constant-Murley shoulder assessment

“…The time of rest between each effort within the test-series, was 10-20 seconds. This is based on earlier research 12,16,19 and no participant commented that they needed more time.…”

Side-to-side differences in range of motion, muscle strength, and medial elbow laxity in young baseball players with medial elbow injuries

“…Bilateral strength of the middle trapezius muscle (MT), LT, SS, and strength of muscle ER/IR were measured using a handheld dynamometer (Mobie, Sakai Medical Co., Ltd, Tokyo, Japan). The validity and reliability of handheld dynamometer measurements in upper extremities have been well documented 11,25,26) . One experienced tester, a physical therapist, performed all the strength measurements.…”