DISCUSSION:
This study demonstrated that the evaluation of the upper limb muscle strength with an isometric dynamometer showed almost perfect reliability as well as reproducibility. In the study by Saccol et al.21, reproducibility of HHD for the internal and external shoulder rotators was evaluated in 20 volunteers placed in supine position using a manual method and in sedestation position using a fixed method, with a rigid device. The ICC values of the non-fixed method determined in this current study, were higher than those determined by Saccol et al.22.
In a study with 12 volunteers, Awatani et al.24measured the reproducibility and reliability of HHD with a non-fixed method for the internal and external shoulder rotators. The intra-examiner ICC value (ICC: 0.94, 95% CI [0.81-0.98]) for the measurement of shoulder internal rotator strength determined by Awatani et al. was lower than the ICC value of 0.96 determined in this current study. On the contrary, the inter-examiner ICC value (0.96 [95% CI: 0.87-0.99]) was higher than the value of 0.93 found in this study.
Dowman et al.25 evaluated the reproducibility of HHD with a non-fixed method for the measurement of elbow flexor and knee extensor strength in 30 patients with interstitial lung disease. The evaluation protocol for the elbow flexors was similar to that of this study. As a result, the reproducibility ICC values were similar to those of this study, ICC 0.98, 95% CI [0.96-0.99] and ICC of 0.97 [0.93-0.99], respectively. This supports the notion that the reproducibility of HHD for evaluation of elbow strength in diverse populations remains high.
This is the first study to evaluate the reproducibility and reliability for ten different upper limb movements, thus demonstrating the clinical importance of this publication. Study limitations include: the absence of non-dominant limb measurements, which is justified by the extension of the evaluation protocol to the ten main upper limb muscle groups; as well as the absence of measurements such as pronation and supination of the elbow, and radial and ulnar deviation of the wrist.
The reproducibility of the evaluation of the upper limb muscle strength with HHD was very good, as was the reliability. The comparison of the fixed and non-fixed method of HHD assessment demonstrated the superior reproducibility and reliability of the non-fixed method in comparison to the fixed method. Only HHD for elbow extensors and external shoulder rotators showed equivalence between the evaluation methods.