METHOD:
The reliability and reproducibility of two HHD methods for evaluating
upper limb muscle strength was assessed and compared using a
prospective, cross-sectional study.
Participants:
Healthy individuals were recruited by direct call, text message or
social network. Participants (male or female) older than 18 years and
who signed the informed consent form were included in this study.
Exclusion criteria included acute bone, muscle or joint diseases,
reduced functional range of motion (ROM)13, presenting
severe heart disease or neuromuscular diseases, or cognitive limitations
that reduced the understanding of motor commands during the evaluation.
Randomization:
The order of the examiner and evaluation method was randomized for all
patients with the use of a draw, which was carried out using a brown
envelope.
Instruments:
Muscle strength was evaluated using a previously calibrated digital
isometric dynamometer, (model 01165, Lafayette Instrument Company,
Sagamore, USA). A goniometer (ISP, Sao Paulo, BR) was used to properly
mark the articular position of the segments for each movement
evaluated14. All patients had the proximal segment
(torso, arm, or forearm) stabilized with the use of an inelastic belt,
in order to nullify the effect of synergistic muscle chains.
Procedures:
The examiners were trained according to the evaluation protocol prior to
testing. The protocol tests the isometric contraction for ten dominant
upper limb muscle groups (shoulder flexors and extensors, shoulder
internal rotators and external rotators, shoulder adductors and
abductors, elbow flexors and extensors, wrist flexors and extensors).
Prior to the measurement, the volunteers were instructed and trained how
to perform each of the movements, and a muscle warm-up was also
performed for each movement.
The fixed method used a system of suction cups adhered to rigid surfaces
that were connected to the dynamometer through a Mulligan inelastic
belt15,16. During the non-fixed method, the examiner
supported the device with one hand, in a direction contrary to the
movement, stabilizing the segment proximal to the moving joint under
assessment14,17-20.
For both evaluation methods, the isometric contraction was sustained for
3 seconds. Each movement was repeated thrice; the largest of the three
values was used. The dynamometer was placed in the distal region
of the forearm, 5 cm from the radial styloid
process21. A muscle recovery time of 90 seconds
between tests was ensured for all measurements14. If
there was visible compensation of synergistic muscles in any of the
movements, the volunteer would be instructed on the correct movement,
and the measurement would be repeated. The positions adopted for the
measurements were based on previous studies (Table
1)14, 17-21.
A minimum resting time of 30 minutes was given between the evaluation of
each examiner22.
Variables of interest:
The concept of reliability is related to the capacity of the instrument
and the evaluation method to generate similar results, even when used by
different examiners. Thus, reliability was obtained by comparing the
highest peak torque of the evaluations for two independent examiners (or
inter-examiner reliability). On the other hand, the reproducibility of
the evaluation method (or intra-examiner reliability) was obtained by
analyzing the similarity between the HHD test and retest by the same
examiner.
Statistical method:
The data were tabulated and analyzed using SPSS (version 21.0,
Statistical Package for the Social Sciences, Chicago, USA). The
qualitative variables were expressed in absolute and relative frequency,
while the quantitative variables were expressed as mean, median,
standard deviation (SD) and 95% confidence interval (95% CI). Analysis
of variance (ANOVA) was used to evaluate the different the peak torque
means obtained from the two methods. The level of significance level was
set at p<0.05.
Prior to recruitment, a sample size calculation based on the results of
a previous study21 determined 25 participants were
sufficient to detect a 10% variation between measurements and a 3% SD
with 80% power with α at 0.05. As this was a cross-sectional study
sample loss was not expected.
Reproducibility and reliability of the tests were calculated using the
intraclass correlation coefficient (ICC) and categorized using the
classifications proposed by Weir (2005)23: “almost
perfect” for values from 1.0 to 0.81, “very good” from 0.80 to 0.61,
“good” from 0.60 to 0.41, “fair” from 0.40 to 0.21, and “low” from
0.20 to 0.00. A Bland-Altman plot was used for the visualization of the
agreement between the quantitative measurements obtained in the tests.