Original Research
Journal of Sport Rehabilitation, 1996, 5, 197-205
0 1996 Human Kinetics Publishers, Inc.
-
Intra- and Intertester Reliability of Chatillon
and MicroFet Hand-Held Dynamometers in
Measuring Force Production
Iris F. Kimura, LouAnne M. Jefferson, Dawn T. Gulick,
and R. David Coll
The purpose of this study was to investigate intratester and intertester reliability when using the Chatillon and MicroFet hand-held dynamometers (HHDs)
to measure isometric force production of the wrist extensors, elbow flexors,
anWe dorsiflexors, and knee extensors. Twelve subjects participated, with each
joint tested four times with each HHD. Intratester and intertester intraclass
correlation coefficients were measured for both devices separately and between the devices. Results indicated that the HHDs were more reliable when
used by a single examiner who had been properly trained in their use. Reliability of the HHDs appears to be affected by both the magnitude of the force
produced by the subject and the examiner's ability to resist the force. There
was no correlation between examiner's stature and consistent force production values. Caution should be taken when interpreting data obtained from
different testers or different HHDs. The same clinician should use the same
HHD for successive tests to yield the most reliable data.
Manual muscle testing (MMT) is an inexpensive, versatile, practical (l2),
and widely accepted form of evaluating muscle strength (2,4, 17, 19, 23). MMT
has advanced from the spring balance (5,29) to the cable tensiometer (20) to the
hand-held dynamometer (HHD), as researchers have attempted to obtain objective
and reliable assessments of muscle strength (3). Objectivity, validity, and reliability are crucial for appropriate diagnosis and treatment. HHDs were designed to
improve and quantify muscle strength assessment (4, 5, 26). Data obtained from
MMT are recorded in nominal, interval, or ratio levels of measurement (16) (Table
I). Despite attempts to standardize MMT, a subjective component (12) is involved
for grades above a level of "fair." Grading reliability may be influenced by the
frame of reference for a "normal" grade and the strength of the examiner (26). For
example, the criteria for "normal" may be different between trained versus untrained clients and stronger versus weaker examiners. However, unlike MMT, evaluation with an HHD does not require subjective judgment by the examiner.
The authors are with Temple University Graduate Athletic Training/Sports Medicine
Program, Pearson Hall, Office 129,Philadelphia, PA 19122. Direct correspondence to Dawn
T. Gulick.
197
198
Kimura, Jefferson, Gulick, and Coll
Table 1 Manual Muscle Testing Grades and Criteria
Manual muscle testing grades
Zero
Trace
Poor
Fair
Good
Normal
0
1
2
3
4
5
0%
1-5%
10-30%
40-60%
70-90%
95-100%
Criteria
No contraction palpated
Contraction palpated with no movement
Movement with gravity eliminated
Movement against gravity
Movement against gravity with resistance
Movement against gravity with maximal resistance
Numerous investigators (6, 12, 13, 18,22,24-28) have evaluated and compared various HHDs and isokinetic devices. However, only four studies (3, 5, 6,
26) have compared various HHDs with each other. The purpose of this study was
to determine intra- and intertester reliability of the MicroFet and the Chatillon
CSDSOO HHDs. In addition, we wanted to compare the data of the two units when
measuring isometric force produced by two upper and two lower extremity muscle
groups.
Methodology
Four female and 8 male NATA-certified athletic trainers (mean age 27.7 f 1.6
years) served as examiners. Each examiner was instructed by a service representative in the proper use of the HHDs. Prior to data collection, examiners practiced
isometric break tests without an HHD and then practiced with each HHD until an
intraclass correlation (ICC) of at least .90 was achieved. Examiners were instructed
in subject positioning, hand positioning, goniometric measurement, and limb stabilization.
Subjects were 3 females and 9 males (mean age 26.4 f 1.3 years). All subjects completed an injury questionnaire designed to eliminate individuals who had
been diagnosed with extremity pathology within 1 year prior to the study. Signed
consent forms were obtained from all subjects.
The Chatillon CSD5OO HHD (Chatillon Medical Products, Greensboro, NC)
is an electronic device that is factory calibrated and designed to measure forces up
to 500 ft-lb. The MicroFet HHD (MicroFet, Draper, UT) is a battery-operated,
microprocessor-controlleddevice with three strain gauges to measure force vectors from three planes. The test range is 0.8 to 100 ft-lb.
Procedures
-
& - - - A < - -
Standard written instructions were utilized throughout data collection. Examiner
and subjecttesting sequences were randomly ordered. Break testing was performed
on the wrist extensors, elbow flexors, ankle dorsiflexors, and knee extensors at the
midpoint in the range of motion (21). The HHD was positioned between the
examiner's hand and the body segment to be tested: - -- - - - -- - - -- - ---
--
Hand-Held Dynamometers
199
All testing positions were standardized (8). When the wrist extensors were
tested, the subject was seated with the forearm supported, elbow flexed to 30°,
and wrist extended to 35O. Stabilization was provided at the midforearm, and
resistance was applied to the distal metacarpals (Figure 1). When the elbow
flexors were tested, the subject was supine with the shoulder in neutral, the
elbow flexed to 75O, and the forearm fully supinated. Stabilization was provided
at the distal humerus, and resistance was applied to the distal forearm (Figure
2). To test the ankle dorsiflexors, the subject was seated over the edge of the
plinth with the knee flexed to 90° and the ankle in 10" of dorsiflexion. Stabilization was provided proximal to the malleoli, and resistance was applied to the
distal metatarsals (Figure 3). For testing the knee extensors, the subject was
seated over the edge of the plinth with a towel roll placed under the distal femur
and the knee flexed to 67.5". The subject's trunk weight was sufficient for stabilization, and resistance was applied 4 cm proximal and anterior to the lateral
malleoli (Figure 4).
Each test began with the examiner counting aloud from 1 to 3 as the subject
gradually increased muscle force so that the maximum force was exerted on the
count of 3. This prevented quick, jerky motions that could have jeopardized transducer pad placement. A11 assessments of force production were performed using a
break test technique in which the examiner provided sufficient counterforce to
move the body segment being tested from the static position. Test-retest sequences
were performed twice at each joint test site with each HHD. A minimum of 30 s
rest was given prior to each retest to avoid fatigue. The force produced during each
effort was recorded by a third examiner.
Figure 1 - Testing position and stabilization for wrist extension using the Chatillon
CSD500 hand-held dynamometer.
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Hand-Held Dynamometers
20 1
Figure 4 - Testing position and stabilization for knee extension using the Chatillon
CSD500 hand-held dynamometer.
Data Analysis
Data analyses were performed using the Biomedical Statistical Software Program
(10) and Excel 4.0 Statistical Software (Microsoft Corporation, Redmond, WA).
Scores from the first and second test-retest sequences were averaged to obtain
Test 1 and Test 2 criterion values for each of the four muscle groups tested. ICCs
(2,l) were performed on the data (9) to determine intratester and intertester
reliabilities for both the Chatillon CSDSOO and MicroFet. An analysis (ICC) was
also performed between the stature of the examiner and the ICCs of each joint
tested; this was done to address the relationship between the examiner's stature
and his or her ability to produce consistent data across the various joints tested.
Results and Discussion
The ICCs for each of the test conditions are summarized in Table 2. Intratester
ICCs were higher than intertester ICCs for both HHDs. ICCs were higher for the
upper extremity joints than for the lower extremity joints for both HHDs. ICCs
were lowest when different joints were tested by different examiners with different
HHDs. ICCs for examiner stature with respect to each joint position tested were as
follows: wrist .30, elbow -.11, ankle .17, and knee .38.
The results of this study revealed moderate to high intratester ICCs for both
the Chatillon and MicroFet. Only two correlations for the Chatillon and five correlations for the MicroFet fell below r = .56. These results are consistent with those
of previous investigators (1, 4, 24, 25) who reported HHDs to be reliable when
Kimura, Jefferson, Gufick, and Coif
202
Table 2 Mean ICCa (9) for Wrist Extension, Elbow Flexion, Ankle Dorsiflexion,
and Knee Extension Between Hand-Held Dynamometers and Among Examiners
Intratester
Chatillon
Microfet
Chatillon vs. Microfet
Intertester
Chatillon
Microfet
Chatillon vs. Microfet
Wrist
extensors
Elbow
flexors
Ankle
dorsiflexors
Knee
extensors
.86
.8 1
.65
.88
.79
.69
.79
.73
.45
.72
.68
.37
.55
.52
.33
.56
.68
.31
.43
.34
.14
.32
.41
.45
aICC= intraclass correlation coefficient.
upper extremity and lower extremity measurements were taken by a single examiner.
The high degree of intratester reliability found in the present study may be attributed
to the standardization of testing protocol and the training of the examiners.
The intertester ICCs were more variable and generally lower than the
intratester ICCs for both HHDs. This was particularly noted when larger muscle
groups were tested. The results displayed in Table 2 reveal lower ICCs for the knee
extensors and ankle dorsiflexors than for the elbow flexors and wrist extensors.
Numerous researchers (1, 7, 14, 22, 28) have suggested that the stature of the
examiner may influence reliability. In the present study, correlations between examiner stature and each joint tested ranged from -.I 1 to .38. These values indicate
that stature and the ability to produce consistent muscle force data are poorly correlated. However, it appears logical that examiners who are stronger, not larger,
should be able to produce more consistent results. Wadsworth et al. (27) studied
the effects of gender, body weight, and grip strength on strength testing with an
HHD. Their results indicated that male and female examiners demonstrated good
interrater reliabilities when testing a female subject. Male examiners also demonstrated good interrater reliabilities when testing a male subject; however, female
examiners demonstrated poor interrater reliabilities when testing elbow flexors
and knee extensors. Results of this study indicated that grip strength was a significant factor and correlated with force values in larger, harder to stabilize muscle
groups. Low forces produced by smaller muscle groups revealed nonsignificant
correlations between body weight and grip strength.
Wikholm and Bohannon (28) reported Pearson Product Moment correlations ranging from .226 to .932. The correlation for weaker muscle groups such as
the shoulder external rotators was r = -932, while the correlation for the elbow was
r = .799 and for the knee r = .226. The authors concluded that as force production
increased, stabilization was compromised. Hayes and Falconer ( 13) reported
intertester ICCs of .89 to .98 and an intratester ICC of .92 for knee extension with
patients who had osteoarthritis. However, force production never exceeded 60 lb.
In the present study of healthy college students, force production ranged from 50
Hand-Held Dynamometers
203
to 148 Ib. Hosting et al. (14) concluded that reliable force measurements using an
HHD were limited to pathologically weakened, naturally weak, or smaller muscle
groups. Since the reliability of HHD measurements is affected by both the magnitude of the forces produced by the subject (22) and the examiner's ability to resist
the subject's force, Brinkmann (6)recommended that the use of HHDs be limited
to muscle groups producing forces of less than 15 kg. A study by Hyde, Goddard,
and Scott (15) revealed that few examiners could consistently apply force greater
than 30 kg. Practitioners need to realize that an isometric break test cannot be
achieved if the examiner is unable to exceed the force production of the subject. If
the subject's force overcomes that of the examiner, then the force measured is the
maximum force of the examiner and not of the subject.
When the two HHDs were tested across various examiners, the force values
recorded were more variable than any of the other comparisons. These results are
consistent with previous investigations (5, 11) which concluded that testing devices should not be used interchangeably.Data obtained via one device should not
be used as a reference for a subject measured with another device.
Conclusion
Both the Chatillon and MicroFet HHDs were found to be reliable devices for MMT
when used by the same examiner. The devices were found to be more reliable for
upper extremity testing than for lower extremity testing. However, using two different HHDs interchangeably on the same subject did not yield reliable data. Therefore, examiners should consistently perform manual muscle tests with the same
HHD in order to gather reliable data.
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Acknowledgments
We wish to extend our appreciation to Chatillon for the loan of the dynamometer.