Walking speed less than 0.8 m/s was selected as the primary outcome for the FNIH Sarcopenia Project because of its strong longitudinal associations with disability and mortality and because its use has been recommended by other experts (refs. (9 (link)) and (10 (link))). Detailed descriptions of gait speed assessment are available elsewhere (10 (link)).
Grip strength was selected as the primary measure of strength for several reasons. It is clearly related to mobility outcomes (4 (link),6 (link),27 (link)) and is easy to use in both clinical and community settings. Standard protocols are available for use without a high level of investigator training, and similar protocols were used across Project studies. Conversely, measures of lower extremity strength were inconsistent across participating studies. Preliminary analysis suggested that grip strength explained a similar amount of variance in walking speed compared with knee extension strength (R2 for grip strength = .01–.16, R2 for knee extension strength = .04–.17).
Grip strength was measured by handheld dynamometer (28 (link)). A summary of study protocols is available in Supplementary Appendix Table 1). The majority of studies (11 out of 13 cohorts) utilized Jamar dynamometers. The maximum strength value in either hand was analyzed.