EFFECT OF FATIGUE INDEX CALCULATION METHOD ON THE QUANTIFICATION OF FATIGUE

Cory R. Schlabs1,Anthony B. Ciccone1, Jake A. Deckert1, Max J. Tilden1,Tércio A.R. Barros2, Trent J. Herda1 & Joseph P. Weir1, FACSM 1University of Kansas, Lawrence, Kansas; 2 University of Nebraska, Lincoln, Nebraska; e-mail: cory.schlabs@gmail.com Repeated maximal effort isokinetic knee extension tests are common in exercise physiology research. However, not all researchers analyze torque data from the same range-of-motion (ROM). Furthermore, fatigue quantification methods of the torque data also differ between studies. The lack of consistent between-study measurement windows and analysis methods may lead to differing interpretations of the same data. PURPOSE: Determine if there is an effect of torque analysis method on the quantification of fatigue index (FI) during repeated maximal effort isokinetic knee extensions. METHODS: Nine healthy males and nine healthy females (age=21.1±1.4 y; height=173.8±12.4 cm; mass=72.1±14.7 kg) completed one bout of 50 repeated maximal effort concentric knee extensions at 180°/s with passive flexion on an isokinetic dynamometer. Position and torque were sampled at 10k Hz. Custom LabVIEW software was used to analyze data. Torque was defined as either peak torque (PT), torque at 135 degrees (T135), torque integral (TI) for the full ROM (TIF), TI for the middle ROM (TIM), or TI for isokinetic load range (TIL). FI was calculated using the following formula: [(start torque – end torque) / start torque]. Four types of FI were calculated using different starting and end torques, respectively: the average torque of repetitions (reps) 1-3 and 48-50 (F3), the average torque of reps 1-5 and 46-50 (F5), the highest three rep torque average and the average torque of reps 48-50 (P3), and the highest five rep torque average and the average torque of reps 46-50 (P5). A four (FI method) x five (torque variable) ANOVA was used. RESULTS: There was a significant interaction between FI method and torque variable. For all torque variables, P3 was greater than F3, F5, and P5. Collapsed across torque variables, the greatest difference was between P3 and F3 (~6%). For torque variables T135, TIM and TIL, F3 was equal to F5. For PT and TIF, F3 was equal to F5 and to P5. For T135 and TIF, P5 was greater than F3 and F5. For TIM and TIL, P5 was less than F3 and F5. For PT, P5 was greater than F5. CONCLUSIONS: Using the data from the same test, for all torque variables, the quantification of fatigue is affected by the repetitions chosen for analysis with the most noticeable effect being P3 suggesting greater fatigue than the other three FI’s for all torque analysis methods