Fatigue resistance measured with pneumatic and hydraulic handgrip systems are not interchangeable

INTRODUCTIONFatigue resistance (FR), as can be measured with the FORTO mobile tooling, here defined as the time (in seconds) during which grip strength drops to 50% of its maximum during sustained contraction, can detect early loss of intrinsic capacity. But different grip strength systems exist and their relationship to frailty remains unclear. Therefore we compared FR obtained by using a pneumatic (Pneu) and hydraulic (Hydr) system.METHODSIn a large sample (n=1381, 18-100y) of (no-)frail: young healthy, middle-aged & old community dwelling persons, and hospitalized patients FR was measured with both systems. 53 community-dwelling women (63–100y) of the sample were categorized according to tertiles on the Frailty Index score (FI) as: low-frail (FI<0.19), intermediate-frail (FI 0.19–0.36), and high-frail (FI>0.36)[1].RESULTSOverall, independent of age category and frailty category, FR measured by Pneu (54.9±34.8s) was higher compared to Hydr (33.7±18.2s,p<0.001). FR, when measured with Pneu was approximately double in low-frail (44.3±24.6s) compared to high-frail participants (23.9±12.7s,p=0.011), whereas FR was similar across frailty groups when measured with Hydr. There was a proportional difference in FR measured with both systems (R2=0.36,p<0.001), highlighting the longer participants could sustain the maximal effort, the higher the difference in FR measured with both systems.DISCUSSIONOur results suggest that Pneu is a more appropriate handgrip system compared with Hydr in a (no-)frail sample. Moreover, Hydr is less able to identify community-dwelling women with higher levels of FR. Pneu assessed FR might be a good additional intrinsic capacity marker to include in frailty tools.1.Theou, O., et al., A comparison of the relationship of 14 performance-based measures with frailty in older women. Applied Physiology, Nutrition & Metabolism, 2011. 36(6): p. 928-938.