title: Reliability and agreement between 2 strength devices used in the newly modified and standardized Constant score.
abstract: OBJECTIVE
  The new and standardized test protocol for the Constant score (CS) provides new methodology, but different devices are still used for shoulder strength testing. It was hypothesized that strength measurements using the IsoForceControl (IFC) dynamometer (MDS Medical Device Solutions, Oberburg, Switzerland) would provide results comparable with the IDO isometer (Innovative Design Orthopaedics, Redditch, UK).
  
  
  METHODS
  Sixty healthy subjects, aged 19 to 83 years, were studied, with 5 men and 5 women in each of 6 ten-year age groups. The IFC and IDO were used in randomized order with an 8-minute interval between testing. Subjects performed 3 successive trials with strong verbal encouragement, with 1 minute between trials. The best strength performance was used in the analysis. The rater and subjects were blinded to all results.
  
  
  RESULTS
  The IFC produced 0.28-kg (0.62-lb) higher strength values on average than the IDO (P = .002). The intraclass correlation coefficient (ICC2,1) was 0.97 (95% confidence interval, 0.95-0.98), whereas the standard error of measurement and smallest real difference were 0.43 kg (0.95 lb) and 1.2 kg (2.63 lb), respectively. The total CS and strength reached mean values of 92.4 points (SD, 6.2 points) and 8.2 kg (SD, 2.6 kg) (18.0 lb [SD, 5.8 lb]), respectively, and were negatively associated with age (r > -0.407, P ≤ .001). The strength values decreased (P ≤ .001) by 1.3 CS points per decade, and women had strength values that were 8 CS points lower on average than those of men of the same age.
  
  
  CONCLUSIONS
  The relative (intraclass correlation coefficient) and absolute (standard error of measurement) reliability between the IFC and IDO is excellent, indicating that performances reported from settings using the IDO are comparable with those recorded with the IFC in other settings.
authors.affiliation: Physical Medicine and Rehabilitation Research-Copenhagen (PMR-C), Copenhagen, Denmark; Department of Physical Therapy, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark; Department of Orthopedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark. Electronic address: mortentange@hotmail.com.
authors.forename: Morten Tange
authors.initials: MT
authors.lastname: Kristensen
authors.affiliation: Faculty of Physical Therapy, Metropolitan University College Copenhagen, Copenhagen, Denmark.
authors.forename: Maria
authors.initials: M
authors.lastname: Aagesen
authors.affiliation: Faculty of Physical Therapy, Metropolitan University College Copenhagen, Copenhagen, Denmark.
authors.forename: Signe
authors.initials: S
authors.lastname: Hjerrild
authors.affiliation: Faculty of Physical Therapy, Metropolitan University College Copenhagen, Copenhagen, Denmark.
authors.forename: Pernille
authors.initials: P
authors.lastname: Lund Skov Larsen
authors.affiliation: Faculty of Physical Therapy, Metropolitan University College Copenhagen, Copenhagen, Denmark.
authors.forename: Bente
authors.initials: B
authors.lastname: Hovmand
authors.affiliation: Department of Orthopedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark; Clinical Orthopaedic Research Hvidovre, Copenhagen, Denmark.
authors.forename: Ilija
authors.initials: I
authors.lastname: Ban
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D011897:Random Allocation; D015203:Reproducibility of Results; D012782:Shoulder / Q000502:physiology*; D013557:Switzerland; D055815:Young Adult
keywords: Constant score; Shoulder; agreement; intrarater reliability; standardization; strength devices