The muscle strength/grip test component measured the isometric grip strength
using a handgrip dynamometer. The goals of this component were to provide: 1)
nationally representative data on muscle strength; 2) prevalence estimates of
children and adults with poor muscle strength; and 3) data to study the
association between muscle strength and other health conditions and risk
factors, such as obesity, physical activity and dietary patterns.
Participants aged 6 years and older, who did not meet any of the exclusion
criteria, were eligible for this component.
Participants were excluded from this component if they were unable to hold
the dynamometer with both hands (e.g., missing both arms, both hands, thumbs on
both hands, or paralyzed in both hands). Participants who were able to grip the
dynamometer with one hand still performed the component. Participants who had
surgery on either hand or wrist in the last three months were not tested on that
Protocol and Procedure
In this component, muscle strength was measured through a grip test using a
handgrip dynamometer. A trained examiner explained and demonstrated the protocol
to the participant. The examiner then adjusted the grip size of the dynamometer
to the participant’s hand size and asked the participant to squeeze the
dynamometer for a practice trial. The practice trial was to determine if the
procedure was understood by the participant and the grip size properly adjusted.
After the practice, the participant was asked to use one of the hands to
squeeze the dynamometer as hard as possible, exhaling while squeezing to avoid
build-up of intra-thoracic pressure. The test was then repeated for the other
hand. Each hand was tested three times, alternating hands between trials with a
60-second rest between measurements on the same hand.
The grip test was performed in the standing position unless the participant
was physically limited. In 2013-2014, among those who were tested, less than
0.3% of the participants younger than 20 years old were tested in a seated
position. Therefore, information on testing position was not released for
participants younger than 20 years due to disclosure concerns. Researchers who
are interested can access this information through the NCHS Research
Data Center. Information on testing position for participants 20 years and
older is included in the present dataset.
Prior conditions may affect a person’s grip strength; therefore, we collected
data on whether the participant has ever had surgery on his/her hands or wrists
for arthritis or carpal tunnel syndrome. In 2013-2014, no one younger than 20
that was tested for grip strength reported ever having hand/wrist surgery for
arthritis or carpal tunnel syndrome. Information on this prior surgery is
released for participants 20 years and over.
The participant was randomly assigned to start the test with his/her dominant
or non-dominant hand. A practice trial was usually performed with the opposite
hand that was assigned to be tested first, unless the participant only had one
hand that was eligible for the test.
Detailed descriptions of the protocol are provided in the NHANES
Muscle Strength/Grip Test Procedure Manual available on the NHANES
Quality Assurance & Quality
Examiners were regularly monitored by NCHS staff and field supervisors.
Retraining sessions were conducted periodically with the examiners to reinforce
the proper protocols and techniques. Inspection, calibration, and maintenance of
the equipment and supplies were performed on a regular basis.
As part of on-going quality control practices, all data were reviewed
systematically for logical or operational inconsistencies and examiner errors.
Data Processing and Editing
During the data processing, edits were made to ensure the logical consistency
and analytic usefulness of the data. Extreme values were reviewed and
cross-checked with other available data.
Grip test status code (MGDEXSTS):
This derived variable
indicates the following for each participant:
1 = Completed test on both hands - the participant performed the test on
2 = Completed test on only one hand - due to
physical limitations, the participant only performed test on one of the
3 = Did not perform test - Grip test did not take
place due to various reasons (such as no time, arrived late/left early,
refusal, illness, emergency, or equipment failure).
Combined grip strength (MGDCGSZ):
The combined grip
strength was calculated as the sum of the largest reading from each hand, and
expressed in kilograms. This variable was not calculated for participants who
only performed the test on one hand.
The NHANES examination sample weights should be used to analyze the muscle
strength/grip test data. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample
weights and other analytic issues.