Now therapists get options for dynamometers such as,
manual dynamometer and digital hand-held dynamometers. But they feel that
digital dynamometers are more convenient than manual dynamometers. Manual
or conventional dynamometer is completely regulated by therapists, and there can
be a high chance of manual/ testing error, and this can be easily avoided when
hand strength is measured by digital dynamometer because it is automated.
It has been seen that the reliability of a digital
dynamometer is greater than a manual dynamometer.
Before diving into the topic, let’s define Reliability.
Reliability refers to the ability of an instrument to
measure a certain value consistently and predictably. Instruments with a high
degree of reliability provide authentic value. They show consistency and
similarity of values between multiple consecutive sessions. Reliability is
expressed in terms of correlation coefficient and standard error of measurement.
Therefore, if you measure patients’ grip strength with
a less reliable instrument, you may end up getting the wrong value. Wrong values
of grip strength (testing errors) may impact the whole therapeutic intervention
programs by misleading you. To avoid these testing errors, you must check the
reliability of the dynamometer; whether it is manual or digital.
When experts check reliability of the dynamometer, they
check total three types of reliability; such as inter-rater reliability,
intra-rater reliability, and test retest reliability.
Inter-rater reliability: It shows the
measurement variation between two or more raters who measure the grip strength
of the same person.
Intra-rater reliability: shows the
variation of measurement data by single rater across two or more trials.
Test-retest reliability: shows the
variation of grip strength evaluated by a single hand dynamometer on the same
person under the same conditions.
Experts have seen that the values of the above three
reliability measures for a digital dynamometer are more correlated than a
manual/ conventional dynamometer. So, you can choose a digital dynamometer over
a conventional one.
Till now we’ve talked about instrumental reliability
and associated testing errors. Now we are going to explain other errors while
measuring the grip strength; such as Gravitational error, injury related errors.
What is Gravitational error?
It is a functional testing error. When our upper limb
moves in the horizontal plane, there will be no gravitational error while
measuring the grip strength. However, it appears when therapists measure grip
strength of the upper limb during vertical movement because upper limbs not only
work against the dynamometer, but also either aided or opposed by gravity. In
most of the cases therapists don’t consider gravitational force during grip
What are Injury related measurement
Hand injury and other hand conditions may cause
measurement issues. If patients’ hands have pain due to trauma or accident or
loss the normal functionality of the index finger or thumb due to injury,
therapists may find different measurements between healthy functional hand and