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% (TTF₁₀₀) and 110% (TTF₁₁₀) of PPO, and the exercises were repeated on a third day. The blood lactate accumulation and the oxygen uptake after exercise were used to estimate the anaerobic lactic and alactic contributions, respectively. Higher values of AC_[La-]+PCr were found after the TTF₁₀₀ compared to TTF₁₁₀ (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 TTF₁₀₀. 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 individual variability must be carefully considered in future studies.