Manual Muscle Testing A Thing of the
Hand-Held Dynamometers may
quickly replace subjective manual techniques
Dr. James Fung, BSc, DC, RTP
Canadian Chiropractor-Vol 8, No
4, June/July 2003
testing (MMT) is commonly used by clinicians and therapists as a tool
for assessment and diagnosis. There are two major roles of MMT in a
chiropractic clinical practice as an indicator to augment or confirm
a normal exam such as that used in applied kinesiology (1) and to
measure the strength of a muscle and identify areas of muscular weakness
due to injury or disease.
weakness, not by confirming strength, MMT provides clinicians with a
useful diagnostic tool. The problem with traditional MMT is that the
results are subject to nature. (2)
the sensitivity of the MMT method is insufficient to assess muscle
strength, at least for grade 4 and higher, and to detect small or
moderate increases of strength over the course of rehabilitation. (3) In
addition, Frese et al. also showed that the accuracy and reliability of
MMT is questionable. (4)
Various types of
hand-held dynamometers (HHD) were developed in an attempt to eliminate
the inherent problems with MMT. In this article we will discuss the use
of various models of HHD to obtain objective, measurable muscle strength
Models of HHD
dynamometers provide a simple, quick, portable, and non-invasive means
of measuring isometric muscle strength. Clinicians and researchers
commonly use either:
(modified pressure cuffs)
Spring gauge dynamometers
Strain gauge dynamometers (5)
sphygmomanometer is easy and inexpensive to use, but values above 210 mm
Hg have a curvilinear relationship with other strength-testing devices.
Higher pressures against the bladder cuff may exceed the underlying
pressure within the cuff to the point that the sphygmomanometer values
drop off at the higher end of the scale. Therefore, it may not be the
best choice for obtaining accurate strength measurements of stronger
muscles. (6) Unlike modified sphygmomanometers, spring gauge
dynamometers have a linear relationship with certified weights
throughout the 27 kg range. However, they tend to lose accuracy with
extended use. (5) Strain gauge dynamometers are the most sensitive. They
maintain a linear relationship with certified weight values. The
sensitivity and accuracy of a strain gauge dynamometer helps to rule out
the instrument as a source of poor reliability. (5) Commercially
available strain gauge dynamometers include MicroFET, Ametek Accuforce
III, MEED 3000 and the Nicholas Manual Muscle Tester.
The MicroFET is
a battery-operated, electromechanical device. It measures, freezes, and
displays the peak force and time duration of muscle testing. The
MicroFET 3 model is sensitive to 0.1 lb.
Studies also show that strain gauge dynamometers exhibit good
reliability and good validity for measuring muscle strength. (5,7)
several aspects of muscle testing procedures that must be considered:
The tester strength must be
high relative to the forces being measured.
Reproducibility of results
depends on the clinician¹s experience.
The time of day as some
patients may fatigue as the day progresses.
Proper stabilization and
position of the patient and the tester.
The dynamometer must be
perpendicular to the limb segment during the tests.
Angle of the joint during
Repeat trial consistency
Some of the HHD
devices available on the market such as the MicroFET models (Diagram 2)
may be connected to a computer software system, which will record and
analyze the results.
Muscle Testing (DMT) validity is based on:
Ten per cent between repeated trials
The presence of cogwheel release
Regional weakness that has no neuroanatomic basis
The interpretation of the time-force curves
The presence of overreaction behaviour.
An example of the muscle testing results profile of a rightflexor
The graph shows the force distribution overtime of five
consecutive trial tests.
The program allows the evaluator
to ensure the repeated trials are consistent. In addition, the MicroFET
3 model also functions as an inclinometer in the same unit (Diagrams 3
3 - Start Position
Diagram 4 - Finish Position
calculates the range of motion by recording the difference between the
starting position and the end position of a specific range of motion.
force and functional ability are not related linearly, maximum force can
be reduced while functional ability is still maintained. (8) For
diagnostic and therapeutic reasons, loss of muscle force should be
detected as early and accurately as possible. (8) Over the recent years
studies have provided reference values for different age groups for
muscle strength obtained by HHD. (8,9,10) Most of these reference values
are established for extremity movements. These age-related reference
values can be employed in a clinical setting to document whether an
individual is impaired relative to a healthy population of the same
gender and age. These values can also help to estimate the severity of
force-generating impairments in patients, to quantify muscle weakness in
individual muscle groups and to evaluate the effects of therapy.
without an HHD, the clinician normally assigns a value to the test
results, such as 1 to 5 or good-fair-poor, depending on how much force
the clinician thought the patient exerted. Problems arise, however,
trying to assign a score based on subjective feeling, especially when
the patient is re-tested at a later date. Many of the problems inherent
to manual muscle testing can be resolved by using an HHD.
MicroFET3 The User Guide.
Noreau L, Vachon J. Comparison of three methods
to assess muscular strength in individuals with spinal cord injury.
Spinal Cord 1998 Oct; 36(10): 716-23.
Frese E. et al. Clinical reliability of manual
muscle testing; Middle trapezius and gluteus medius muscles. Phys
Ther 1987 Jul; 67(7): 1072-6.
A. Williams Andrews PT, Hand-held dynamometry for
measuring muscle strength, Journal of Human Muscle Performance 1991;
1 (1) 35-50.
Bohannon RW, Lusardi MM. Modified
sphygmomanometer versus strain gauge hand-held dynamometer. Arch
Phys Med Rehabil 1991; 72 (11): 911-4
Bohannon RW. Intertester reliability of hand-held
dynamometry: a concise summary of published research. Percept Mot
Skills 1999 Jun; 88: 899-902.
Beenakker EA Et al. Reference values for
isometric muscle force obtained in 270 children aged 4-16 years by
hand-held dynamometry. Neuromuscul Disorder 2001 Jul; 11(5): 441-6.
Bohannon RW. Reference values for extremity
muscle strength obtained by hand-held dynamometry from adults aged
20-79 years. Arch Phys Med Rehabil 1997 Jan; 78 (1): 1442-3.
Andrews AW, Et al. Normative values for isometric
muscle force measurements obtained with hand-held dynamometers. Phys
Ther 1996 Mar; 76(3): 248-59.
Dr. James Fung graduated from
the University of Toronto in 1997 with a Hon BSc degree in molecular
genetics. He is a 2001 graduate of CMCC. He currently maintains two
practices in Toronto. He is also a certified instructor in the Trigenics