Reliability of an intermittent handgrip fatiguing protocol

The purpose of this study was to determine the test–retest reliability of critical force (F_Cr), peak force (Y0), and k (rate constant), during a 5-min intermittent handgrip fatiguing protocol.

Seventeen males (n = 8) and females (n = 9) between the ages of 18–55 years old (23.94 ± 6.21 y; 169.16 ± 7.62 cm; 74.24 ± 12.91 kg; 25.74 ± 9.35%body fat) completed this study. On visit 1, participants completed informed consent, eligibility screening, and a demographics questionnaire. On Visit 2, participants completed anthropometric assessments (height, weight, body composition) and familiarization trials. Visits 3 and 4 consisted of a maximal voluntary contraction (MVC) to determine warm-up intensity, a standardized warm-up, additional MVCs, and an intermittent handgrip fatiguing protocol, during which participants completed 60 repeated 4-s maximal effort isometric contractions with 1 s of rest for a total of 5 min. Intraclass correlation coefficients (ICCs), as well as standard error of measurement (SEM), the minimal difference (MD), and 95% confidence intervals for mean differences were used to examine reliability of dependent variables during the handgrip fatiguing protocol between visits 3 and 4.

Results indicate good reliability for F_Cr (ICC_2,1 = 0.820, SEM = 1.17 kgf, MD = 3.24 kgf, 95% CI 0.626–0.919)_, Y0 (ICC_2,1 = 0.944, SEM = 2.00 kgf, MD = 5.54 kgf, 95% CI 0.891 to 0.972)_, and k (ICC_2,1 = 0.831, SEM = 0.003 s⁻¹, MD = 0.007 s⁻¹, 95% CI 0.649–0.925).

In conclusion, the intermittent handgrip fatiguing protocol utilizing a 4:1 s duty cycle showed good reliability for F_Cr, Y0, and k.