Abstract

Background: There appears to be an undisputed strong relationship between isometric handgrip strength (HGS) and functional fitness test performance, ability to perform activities of daily living (ADLs), and mortality, but the extreme diversity in how HGS data are interpreted make it difficult to utilize the assessment in a meaningful way. The present study aimed to simplify this interpretation by establishing a single and meaningful universal HGS cutoff that would inform the test administrator whether or not additional functional fitness testing was warranted. It was hypothesized that subjects scoring above the HGS cutoff would self-report fewer functional limitations, compared with subjects scoring below the cutoff. It was also hypothesized that subjects scoring above the HGS would perform better on each functional fitness test outcome, compared with subjects scoring below the cutoff.

Methods: Male (n=24; Age=62.3±14.3 years) and female (n=59; Age=64.7±13.0 years) subjects were recruited to take part in the Steps Taken Against Neuromuscular Decline (STAND) Initiative, a longitudinal study of aging. The present study is a cross-sectional assessment of the baseline data from the first 83 subjects. Subjects self-reported their perceived ability to complete the variety of ADLs included in the Composite Physical Function Scale (maximum score of 24 indicating no perceived functional limitations). They additionally completed a battery of functional fitness assessments, which included HGS, 30-s Chair Stand, 8-ft Up-and-Go, 10 lb and 25 lb lift and carry, and 400 m Walk Test. A self-developed cell phone application was utilized to produce more outcomes, such as steady-state gait speed and cadence during the 400 m Walk Test. Independent samples t-tests were used to compare the perceived and actual functional fitness outcomes between subjects with grip strength <30 kg and those with grip strength ≥30 kg. Additionally, positive predictive value (PPV) and negative predictive value (NPV) were calculated to investigate the accuracy of a 30 kg HGS cutoff to identify subjects with perceived functional limitations (indicated by a CPF Scale score <24) or actual functional limitations (indicated by scoring below 2 standard deviations from the mean of the reference group, subjects with HGS ≥30 kg).

Results: Subjects with a HGS ≥30 kg scored significantly higher on the CPF Scale, compared with subjects with a HGS <30 kg (23.9+/- vs. 22.4+/-3.3, respectively). Likewise, subjects with a HGS ≥30 kg performed significantly better on every functional fitness test outcome, compared with subjects with a HGS <30 kg. The NPV (true negative) was excellent (≥90%) for all outcomes, while the PPV (true positive) was poor (≤ 56%) for all outcomes.

Conclusions: A HGS ≥ 30 kg appears to be an appropriate cutoff to accurately rule out current functional limitations in males and females 40 years of age and older, but it is not suitable to accurately identify individuals with current functional limitations. It is suggested that individuals with a HGS <30 kg undergo additional functional tests to identify any limitations that may exist.

Keywords: Senior Fitness Test, 30-s Chair Stand, 8-ft Up-and-Go, 400 m Walk Test, gait assessment, older adults, activities of daily living, self-efficacy