Therefore, in the clinical implementation of a muscle strength evaluation method using an HHD, it is necessary to set the predicted value for the maximum muscle strength, dependent on the characteristics of the subject, as an indicator for the maximum muscle strength that the subject should possess.
As body weight and limb segment length are used in calculating the theoretical Grade 3 muscle strength value, they are dependent on the subject's individual physique; thus, the theoretical Grade 3 muscle strength value can serve as an indicator for the maximum muscle strength that each subject should possess in a relative evaluation of muscle strength values obtained via measurement using an HHD.
After calculating theoretical Grade 3 muscle strength values from body weight and limb segment length for each experimental task, measuring the actual isometric maximum muscle strength using an HHD, and performing a test for noncorrelation and regression analysis, we found a linear relationship between the maximum muscle strength value and the theoretical Grade 3 muscle strength value for each of the eight experimental tasks.
Most HHDs measure the isometric type of contraction, and isokinetic dynamometers can test the strength of both concentric and eccentric contractions.
These include HHDs, handgrip dynamometers, and isokinetic dynamometers.
HHDs, also known as myometers, have several advantages over other types of dynamometers, including lower cost, greater ease of use, and better acceptability in clinical settings.
Several studies have examined the reliability of HHDs with different types of individual (1-3, 15).
Tester 1 (university professor, PhD) had extensive experience in the use of HHDs for assessing muscular strength in individuals with physical disabilities.
Despite its advantages, reports on HHD reproducibility and repeatability were controversial [15-18].
HHD strength measurements can be performed according to two methods : (i) the "make test," in which the examiner holds the dynamometer stable while the subject exerts a maximal force against it, and (ii) the "break test," in which the examiner overcomes the maximum force exerted by the subject, producing a small limb movement in the opposite direction of patient's force.
A novel HHD (Industrial Research Limited, Christchurch, New Zealand) was used that measures muscle force and joint range of motion simultaneously (Figure 1).
Overall our study showed "very high" reliability for strength measures using a HHD in a cohort of patients with chronic diseases.