## 3 Is the COP a New and Reliable Marker? The COP is a relatively recent marker of cardiovascular risk. It was initially documented in 2012 by [PERSON] et al. [17] and subsequently corroborated by other studies as an additional non-invasive prognostic marker of interest in the field of cardiology [17; 19; 20; 21; 23; 28]. Despite the limited number of publications on this topic that relate to healthy individuals, preliminary studies have indicated its potential utility as a predictive tool for assessing mortality and cardiovascular risk [16; 17; 18; 19], especially in patients with a previous diagnosis of HF [22; 25; 26]. As mentioned above, one of the main advantages of the COP is that it can be measured relatively easily during submaximal exercise tests on a treadmill or stationary bicycle, as opposed to other available markers such as oxygen \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{**Prognostic**} & \multicolumn{2}{c}{**Number of**} & \multicolumn{1}{c}{**Cut-Point Values for Poor Prognostic**} \\ \multicolumn{1}{c}{**Variable**} & \multicolumn{1}{c}{**Patients**} & \multicolumn{1}{c}{**Cut-Point Values for Poor Prognostic**} \\ \hline Peak \(V^{\prime}\)O\({}_{2}\) & [PERSON] et al. [3] & 114 & \textless{}14 mL/kg.min\({}^{-1}\) \\  & [PERSON] et al. [4] & 644 & \textless{}10 mL/kg.min\({}^{-1}\) \\  & [PERSON] et al. [2] & 181 & \textless{}50\% of predicted \\ \(V^{\prime}\)E-\(V^{\prime}\)CO\({}_{2}\) slope & [PERSON] et al. [5] & 173 & \textgreater{}34 \\  & [PERSON] et al. [7] & 600 & \textgreater{}34 \\ Periodic breathing & [PERSON] et al. [6] & 323 & PB \textgreater{}60\% of time, amplitude \textgreater{} 14\% \\  & [PERSON] et al. [8] & 84 & More than 2 regular oscillations, amplitude \textgreater{} 5 L \\ \(\Delta V^{\prime}\)O\({}_{2}\)/\(\Delta\)WR & [PERSON] et al. [9] & 385 & \textless{}7 \\ \(V^{\prime}\)O\({}_{2}\) kinetics in the recovery & [PERSON] et al. [10] & 153 & Peak \(V^{\prime}\)O\({}_{2}\)\textgreater{} 39\% of predicted and R \(V^{\prime}\)O\({}_{2}\)\textless{} 2.5 \\  & [PERSON] et al. [11] & 196 & \textless{}T\({}_{1/2}\)\(V^{\prime}\)O\({}_{2}\) peak \textgreater{} 200 s \\ Circulatory power & [PERSON] et al. [12] & 175 & \textless{}3.047 mL/(kg.min\({}^{-1}\)) mm Hg \\  & [PERSON] et al. [13] & 154 & \textless{}5.000\% mm Hg \\ COP & [PERSON] et al. [20] & 2205 & \textgreater{}23.3 \\  & [PERSON] et al. [21] & 3160 & \textgreater{}24.3 \\  & [PERSON] et al. [23] & 2190 & \textgreater{}29 \\  & [PERSON] et al. [24] & 3160 & \textgreater{}24 \\  & [PERSON] et al. [25] & 2190 & \textgreater{}23.3 \\  & [PERSON] et al. [26] & 2205 & \textgreater{}26 \\  & [PERSON] et al. [17] & 277 & Low: \textless{}26.0; Moderate: 26.0–30.7; high: \textgreater{}30.7 \\  & [PERSON] et al. [27] & 30 & \textgreater{}36 \\ \hline \hline \end{tabular}  
* \(\Delta V^{\prime}\)O\({}_{2}\)/\(\Delta\)WR indicates delta oxygen-uptake/delta-work-rate slope; peak \(V^{\prime}\)O\({}_{2}\) peak oxygen uptake; R \(V^{\prime}\)O\({}_{2}\), the ratio between total \(V^{\prime}\)O\({}_{2}\) during and after exercise; T\({}_{1/2}\)\(V^{\prime}\)O\({}_{2}\) peak, time to reach 50% of peak oxygen uptake during recovery; \(V^{\prime}\)E-\(V^{\prime}\)CO\({}_{2}\) slope, the ratio of the increase in minute ventilation to the increase in carbon dioxide output expressed as a slope; and COP, cardiorespiratory optimal point.  
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Table 1: Cut-point values for prognostic variables derived from cardiopulmonary exercise testing. consumption [21]. Recent studies have suggested that the COP may better indicate cardiovascular disease risk than other traditional markers [21; 23]. In addition, research has shown that lower COP values are associated with a reduced risk of coronary artery disease, stroke, and HF [25]. The concept of the COP is important in exercise physiology [17; 19; 20; 22; 23; 25; 26; 28]. The literature defines the COP as the highest level of interaction between the efficiencies of the cardiovascular and respiratory systems [17; 19; 23].