Ratio between muscle fatigability and selfperceived tiredness could be an important parameter for characterizing frailty

Objective:Muscle fatigability is an important indicator of reduced intrinsic capacity, and therefore potentially an early characteristic of frailty. Meanwhile, self-perceived fatigue can be considered as a symptom of reduced intrinsic capacity. The aimof this study was to investigate whether older adults with low muscle fatigability and high feelings of fatigue are more prone to frailty. Methods: 444 robust or prefrail participants of the BUTTERFLY-study, a cohort study in well functioning subjects aged 80+, were assessed for frailty score on Frailty Index of Fried (FFI), Groningen Frailty Indicator (GFI) and the Rockwood Index (RWI). Self-perceived fatigue was assessed by the Multidimensional Fatigue Index (MFI), muscle fatigability was measured with the Martin Vigorimeter, and expressed as grip work (GW=0.75 ∗ maximal grip strength ∗ time for maximal grip strength to decrease to 50% during sustained contraction). Statistical analyses were corrected for age and sex. Results: Prefrail subjects showed significantly worse muscle fatigability and feel more fatigued than their robust counterparts (p