Jl. Malerba et al., RELIABILITY OF DYNAMIC AND ISOMETRIC TESTING OF SHOULDER EXTERNAL ANDINTERNAL ROTATORS, The Journal of orthopaedic and sports physical therapy, 18(4), 1993, pp. 543-552
Advances in isokinetic technology allow the physical therapist to asse
ss concentric, eccentric, and isometric muscle performance at the shou
lder in various positions. Research is limited, however, on the reliab
ility of isokinetic measurements. The purposes of this study were: 1)
to determine the test-retest reliability of concentric, eccentric, and
isometric muscle performance measurements of shoulder external and in
ternal rotation in the scapular plane test position and 2) to compare
this reliability between the involved and uninvolved limb of subjects
with a history of unilateral shoulder pathology. Fourteen males and 10
females (17-58 years) were tested on two occasions at 1-week interval
s with the Biodex isokinetic dynamometer. Peak torque, total work, and
average power were recorded for concentric tests at angular velocitie
s of 60 and 120-degrees/sec and for eccentric tests at 60-degrees/sec.
Maximum average isometric torque was recorded in two positions. Means
, standard deviations, and mean differences between sessions with 95%
confidence intervals were calculated. Intraclass correlation coefficie
nts (ICCs) were used to determine test-retest reliability. Isometric t
ests were generally most reliable (ICC = .81-.93), followed by concent
ric (ICC = .60-.95) and eccentric tests (ICC = .44-.92). Isokinetic an
d isometric reliability were usually higher for involved than uninvolv
ed shoulders. The implication of these findings is that there appears
to be greater variability with eccentric than concentric or isometric
testing of shoulder rotation. Factors that possibly contributed to var
iability are discussed. Clinicians should recognize potential sources
of testing error when obtaining isokinetic measurements for use in cli
nical decision-making. Further refinement of isokinetic testing protoc
ols at the shoulder is recommended.