Longitudinal Stability of The Handgrip Strength Measurements in University Students.

Handgrip strength, a component of physical fitness tests and a biomarker of future health, is typically measured annually. However, no studies have looked at the consistency of these measurements over time. We investigated the reliability of handgrip strength measurements among university students who take the test annually. Our data included 3649 students (2769 males and 880 females) who were tested annually over their four years in university. Results showed a significant difference in absolute errors across the three test-retest intervals (p < 0.001). Specifically, the 1-year longitudinal reproducibility was significantly better than the reproducibility at 2-years and 3-years. There were no differences in longitudinal reproducibility between the 2-year and 3-year time points (p = 0.490). The minimal difference values at the 1-year, 2-year, and 3-year time points were 7.70, 8.33, and 8.35 kg, respectively. When comparing the percentage of coefficient variation (%CV) values, the reliability was better in males than in females (p = 0.025). The difference in the %CV between sexes was 0.27 (95% CI: 0.03-0.52) %. When examining the results using absolute error, the results were reversed, with females having lower absolute error values than males (p < 0.001). The reliability values were better for the digital handgrip device as compared to the analog device (p < 0.001). These findings can help evaluate the consistency of handgrip strength measurements made annually. When measured annually in young adults, a change of at least approximately 20% (calculated using %MD in both sexes) in the measured values is necessary to indicate a change confidently.