# Does Power Output at Critical Power Intensity Interchange between Cycling and Running?
###### Abstract  
The differences in power meters and gestures between cycling and running can have an impact on determining Critical Power (CP) intensity in each sport. CP is a concept that has been extensively researched in cycling, but with the advent of power measurement in running, it can now be examined in that discipline as well. The purpose of the present study was to determine whether power output at CP intensity is interchangeable between cycling and running segments measured with their respective discipline-specific power meters. A group of 18 trained triathletes (age 33.0 \(\pm\) 11.1 years, height 1.75 \(\pm\) 0.06 m, body mass 71.2 \(\pm\) 7.1 kg) performed a CP test in cycling (3-min All-Out Test) and running (9/3-min Stryd CP Test). The main results of the present study showed significant differences (\(p<0.001\)) between CP in cycling and running. The running CP (301.8 W \(\pm\) 41.5 W) was 20.2% overestimated compared with the cycling CP (251.1 W \(\pm\) 37.0 W). Cycling power only explained 26.7% of the running power (\(R^{2}=0.267;p=0.284\)). Therefore, power would not be interchangeable between the cycling and running disciplines at CP intensity. In conclusion, it would be necessary to carry out a specific test for each discipline to be able to make a correct determination of CP. s +
Footnote †: journal: _Sci._  
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this investigation with the running segment. This is essential to correctly understand the concept of power in the running segment. It is also important to note that performance in the cycling segment shows the best concordance with overall performance for both elite men and elite women at both sprint distances [11], as performance in the cycling segment shows the best concordance with overall performance as well as at Olympic distances [12]. In cycling, the increasing availability of power meters has led some authors [13] to associate a certain watt value to Functional Threshold Power (FTP) and other concepts such as Critical Power (CP). Currently, with the capability to calculate running power, these concepts have expanded within the sport. [PERSON] and [PERSON] [13] defined FTP as the highest power that can be maintained for 1 h. The Running Functional Threshold Power (rFTPw), measured in watts (W), is a measure of power associated with a certain intensity that can be calculated theoretically through a complex calculation model [14]. When using off-the-shelf power meters such as the Stryd Summit Power Meter (Boulder, CO, USA), data can be uploaded from various tests [15] to calculate the rFTPw or CP in the \"Power Center\" ([[https://www.stryd.com/powercenter](https://www.stryd.com/powercenter)]([https://www.stryd.com/powercenter](https://www.stryd.com/powercenter)), accessed 10 February 2023), which can be used to predict race times for different distances. However, a study of comparison between different tests to determine rFTPw concluded that it varies depending on the test performed and its duration [16]. The literature has explored the concept of CP from both a physiological and a mathematical point of view. Mathematically, CP is defined as the power asymptote of the hyperbolic relationship between power output and time to exhaustion [17]. For longer endurance events, it has been suggested that CP is most relevant to continuous activities lasting around 2 to 30 min [17]. This concept has also been applied to other sports, such as running [18], where the treadmill velocity-endurance time relationship for runs of 2 to 12 min duration conform to a similar hyperbolic function as that described for cycle ergometry [19]. From a physiological standpoint, CP represents the boundary between the steady state and a nonsteady state. As a result, it may offer a more significant performance indicator compared to other established benchmarks of aerobic fitness, such as maximal O\({}_{2}\) uptake and the lactate threshold [17].