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 particular hand.
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 website.
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.
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:
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.