To assess intra- and inter-tester reliability of measuring shoulder strength using a new hand-held dynamometer.
Methods
On two occasions, two examiners (blinded to output) measured seven separate tests of shoulder strength. Twenty-three participants with no shoulder symptoms were tested bilaterally. Each test was performed three times as a ‘make test’ using a hand-held digital dynamometer.
Results
Intraclass correlation coefficients (2,1) and (2,3), 95% confidence intervals and standard errors of measurements (SEM) demonstrated good intra- and inter-tester reliability of all tests [ICC(2,3) >0.87], with the exception of inter-tester reliability of right abduction [ICC(2,3) = 0.77]. Greater reliability of all tests was demonstrated when the mean of three trials was used compared to the first measurement. Intra-tester reliability of all tests using ICC(2,1) ranged from 0.74 to 0.98; ICC(2,3) ranged from 0.89 to 0.98. Inter-tester reliability using ICC(2,1) ranged from 0.52 to 0.94; ICC(2,3) ranged from 0.77 to 0.96. The smallest detectable difference (SDD), used to measure precision, ranged from 5.9 to 12.5 Newtons.
Discussion
The findings obtained in the present study suggest that using the methods employed in the population investigated demonstrated good to excellent intra- and inter-tester reliability for the measurement of shoulder strength. The SEM and SDD findings provide guidance for values that may be considered as a real change in strength.
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