Reliability of anaerobic contributions during a single exhaustive knee-extensor exercise.

The total anaerobic contribution (AC [La-]+PCr ) is a valid and reliable methodology. However, the active muscle mass plays an important role in the AC [La-]+PCr determination, which might influence its reliability. Thus, this study aimed to investigate the effects of two exhaustive intensities on the reliability of the AC [La-]+PCr during a one-legged knee extension (1L-KE) exercise. Thirteen physically active males were submitted to a graded exercise to determine the peak power output (PPO) in the 1L-KE. Then, two constant-load exercises were conducted to task failure at 100% (TTF 100 ) and 110% (TTF 110 ) of PPO and repeated on a third day. The blood lactate accumulation and the oxygen uptake after exercise were used to estimate the anaerobic lactic and anaerobic alactic contributions, respectively. Higher values of AC [La-]+PCr were found after the TTF 100 compared to TTF 110 (p = 0.042). In addition, no significant differences (p = 0.432), low systematic error (80.9 mL), and a significant ICC (0.71; p = 0.004) were found for AC [La-]+PCr in the TTF 100 . However, an elevated coefficient of variation was found (13.7 %). In conclusion, we suggest the use of the exhaustive efforts performed at 100% of the PPO with the 1L-KE model, but its elevated variability must be carefully considered in future studies.