Fatigue at your fingertips: Can a brief handgrip task reveal your subjective fatigue state?

Fatigue is a complex concept that includes both subjective sensations and objectively measurable performance decline (fatigability). There is a need for simple, reliable tools to assess fatigability in both clinical and athletic settings. This pilot study examined whether a 30 second (s) maximal isometric handgrip test could serve as an objective marker of fatigability and reflect perceived fatigue. Nineteen healthy volunteers (4 women; 33.2 ± 12.1 years) completed six testing sessions (morning and afternoon). Participants performed a 30 s sustained maximal handgrip contraction with a custom dynamometer. The primary outcome was the percentage decline in force (ΔMVC), complemented by mechanical impulse (IMP). Subjective measures included the Rate of Fatigue (ROF), Hooper Index, Rating of Perceived Exertion, and motivation. Greater ΔMVC was moderately associated with higher perceived fatigue (e.g., ROF: r = 0.37 at 15 s, p < 0.002) and lower motivation (r = -0.47 at 30 s, p < 0.0002). Motivation emerged as the most consistent predictor of both ΔMVC and IMP. Diurnal variation was observed, with larger declines in the afternoon compared to morning (39.1 ± 8.2% vs 36.4 ± 6.9%, p = 0.015), alongside higher self-reported fatigue. Among the four time points assessed, ΔMVC@15 s showed the most consistent associations with subjective markers, suggesting that shorter efforts (i.e. 15 s) may capture similar information while improving comfort and reliability. The 30 s handgrip test is repeatable and sensitive to diurnal variation and objective performance decline but only moderately reflects subjective fatigue. With further validation, brief handgrip endurance tests could complement self-report measures for fatigue monitoring in both clinical and sports contexts.