# Does Power Output at Critical Power Intensity Interchange between Cycling and Running?
## 4 Discussion
Therefore, the CP in cycling determined with the 3-min All-Out test [26; 27] was considered to be 100% (251.1 W \(\pm\) 37.0 W) due to its importance as the primary indicator of external load in this sport [10], as well as its consistent theoretical basis for use and application of power [10; 13; 30; 31; 32; 33; 34]. In contrast, the watts corresponding to the running CP determined with the 9/3-minute Stryd CP were overestimated by 20.2% (301.78 W \(\pm\) 41.55 W) compared with the cycling CP. On one hand, the results of the present study could be partially explained by transferability of running and cycling training zones in triathletes [1]. This study suggests that triathletes should perform sport-specific testing to assess training zones for cycling and running. Consistently with this recommendation, our results showed that power output in cycling explained only 26.7% of the running power output (\(R^{2}\) = 0.267; \(p\) = 0.284). In addition, significant differences and large ESs were found between cycling and running CP in both absolute power output (\(p\) < 0.05; ES = 1.29) and power output relative to body mass (\(p\) < 0.05; ES = 1.25). Therefore, it is necessary to carry out a specific test for each discipline to make a correct determination of CP. The hypothesis that power output is not interchangeable between the cycling and running disciplines at CP intensity would be acceptable. One of the main reasons for this is the differences in specific gestures between each sport, as well as differences in power meters. On the other hand, previous research has shown that there is a relationship between variables such as heart rate and VO2 max obtained during cycloergometer and running tests, which suggests that athletes can use only one mode of testing to determine their training guidelines [49]. However, the present study data indicates that this statement applies only to certain physiological variables of internal-load variables, not to external-load variables such as power. From a practical point of view, in multisport activities such as triathlon, coaches and athletes should focus on improving their cycling and running segments due to their significant impact on overall performance [11; 12]. Nevertheless, it is important to consider the limitations of this study, such as the variability of CP protocols [50; 51], the varying levels of performance for each segment of the triathletes, the technical difficulties of running compared to cycling, and the differences in the power meters used for each sport. To minimize the effect of these limitations, the most commonly used tests for determination of CP in cycling and running have been carried out [20; 26; 27], this study was performed on a population of triathletes familiar with both sports, and a single model of power meter was used for CP determination in each sport. Future studies should investigate the possibility of extrapolating power output at CP intensity between the cycling and running segments in triathletes of different levels (highly trained, elite, and world-class) and sexes (female). These studies should also compare different protocols for CP determination in both cycling and running to provide information on the best power records for different levels and sexes, which would allow ranking of athletes according to their Record Power Profiles. The data from our study can serve as a foundation for comparing cycling and running power data in trained triathletes.