# Power Profile Index: An Adjustable Metric for Load Monitoring in Road Cycling
## 4 Discussion  
This study proposed PPi, a new multifactorial method for quantifying cycling exercise load (i.e., intensity \(\times\) volume) based on the individual power profile. This index is intended to overcome some of the limitations found in other load quantification indices currently in use, such as TRIMP or TSS. For example, TRIMP is not able to reflect short, very high intensity efforts due to the delayed HR response [13], while TSS does not sufficiently weight intensity to volume (e.g., a maximum effort in one hour, such as the UCI Hour Record,  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Time Trial** & **Flat** & **Medium Mountain** & **High Mountain** & \(p\) \\ \hline \multirow{2}{*}{PPi} & 32.9 \(\pm\) 6.2 & 29.9 \(\pm\) 2.3 & 32.5 \(\pm\) 3.4 & 32.9 \(\pm\) 3.3 & \multirow{2}{*}{0.292} \\  & (18.8\%) & (7.7\%) & (10.5\%) & (10.0\%) & \\ \multirow{2}{*}{RPE} & 8.0 \(\pm\) 1.0 & 5.8 \(\pm\) 1.2 & 7.0 \(\pm\) 0.5 & 8.4 \(\pm\) 0.8 & \multirow{2}{*}{\textless}0.001 \\  & (12.5\%) & (20.7\%) & (7.1\%) & (9.5\%) & \\ \multirow{2}{*}{ TSS} & 58.0 \(\pm\) 0.8 & 159.3 \(\pm\) 25.8 & 220.2 \(\pm\) 22.0 & 252.3 \(\pm\) 49.6 & \multirow{2}{*}{\textless}0.001 \\  & (1.4\%) & (16.2\%) & (10.0\%) & (19.7\%) & \\ \multirow{2}{*}{eTRIMP} & 143.0 \(\pm\) 57.3 & 606.1 \(\pm\) 130.2 & 767.3 \(\pm\) 118.1 & 816.6 \(\pm\) 172.7 & \multirow{2}{*}{\textless}0.001 \\  & (40.1\%) & (21.5\%) & (15.4\%) & (21.1\%) & \\ \hline \end{tabular} Data are presented as Mean \(\pm\) SD, with CV in parentheses. PPi, power profile index; RPE, rate of perceived exertion; TSS, training stress score; eTRIMP, [PERSON]’s training impulse.  
\end{table}
Table 4: Differences in the intensity quantification indexes regarding the stage type during the 2018 Tour de France.  
Figure 2: Comparison of the Power Profile Index against current intensity quantification methods. Data from 2018 Tour de France. TSS, training stress score; PPi, power profile index; RPE, rate of perceive exertion; eTRIMP, [PERSON]’s training impulse; MM, medium mountain; HM, high mountain; ITT, individual time trial.  
which causes great fatigue, is 100 TSS, while a light effort of 3 h at 60% of the FTP is 106 TSS).  
The PPi has been designed as a new index capable of quantifying the high intensity efforts made by cyclists during a training session or competition, considering the time spent at a given PO and weighting the intensity according to power zones (Z1 to Z6) and the type of competition. The comparison against current methods suggested that PPi may be a more stable index to quantify cycling exercise load. This could help coaches in the process of load quantification and training planning by providing a more comprehensive view of high-intensity efforts.  
To the best of our knowledge, this is the first index adjusted by stage type (prologue, time trial, flat, and high mountain) in an attempt to solve existing problems inherent in the current indexes in discriminating maximal efforts, regardless of the type of competition. In addition, because the PPi is based on a cyclist's power profile, data can be automatically obtained in an individualized manner from real athlete performance and adjusted at a preferred time window. For this purpose, we provide an open-access chart in the specialized software WKO5 to easily calculate the PPi.