IJCS | Volume 31, Nº4, July / August 2018

330 de Souza e Silva et al. Cardiorespiratory optimal point in soccer players Int J Cardiovasc Sci. 2018;31(4)323-332 Original Article backs (14.33 km.h -1 ) and midfielders (14.11 km.h -1 ). Nevertheless, it is worth noting that the heterogeneity of the methods used to measure VT hinders the comparison of the results between the studies. Finally, the COP failed to show a linear association with the variables VT and VO 2 max. Ramos et al. 15 have not only described a moderate association with VO 2 max (-0.47) and VT (-0.42), but have also observed that the combination of COP and VO 2 max adds more prognostic information to all-cause mortality than each variable in isolation. 17 Such findings suggest a possible independence and complementarity of COP regarding VO 2 max and VT, which could contribute with additional information to the interpretation of the relationship between the cardiovascular and respiratory systems during a CPX. Thus, one can speculate that the submaximal variables – COP and VT – might better reflect the energetic demands of a soccer match in the current context, in which the differences in distance and in percentage of time spent in intense efforts are less evident in soccer players of different field positions. The present study has some limitations in addition to those already mentioned. The CPX analyzed were limited to those performed in the pre-season period, not allowing us to assess the COP behavior in different training periods of the soccer players. In addition, this study only assessedmale adult elite soccer players, which limits the extrapolation of the results to female soccer players, other age groups, different technical levels and other sport modalities. Conclusion The present study described the COP behavior and its absence of associationwith VO 2 max andVT of male adult elite soccer players. Thus, future studies are required to assess whether COP can provide additional and relevant information to other sport contexts. Author contributions Conception and design of the research: de Souza e Silva CG, Castro CLB, Franca JF, Bottino A, Myers J, Araújo CGS; Acquisition of data: Castro CLB, Franca JF, Araújo CGS; Analysis and interpretation of the data, Statistical analysis and Writing of the manuscript: de Souza e Silva CG, Araújo CGS; Critical revision of the manuscript for intellectual content: Castro CLB, Franca JF, Bottino A, Myers J, Araújo CGS. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This study is not associated with any thesis or dissertation work. Ethics approval and consent to participate This study was approved by the Ethics Committee of the Suprema - Faculdade de Ciências Médicas e da Saúde de Juiz de Fora under the protocol number 0218/11. All the procedures in this studywere in accordance with the 1975 Helsinki Declaration, updated in 2013. Informed consent was obtained from all participants included in the study. 1. Albouaini K, EgredM, Alahmar A, Wright DJ. Cardiopulmonary exercise testing and its application. Postgrad Med J. 2007;83(985):675-82. 2. Ross R, Blair SN, Arena R, Church TS, Després JP, Franklin BA, et al; American Heart Association Physical Activity Committee of the Council on Lifestyle andCardiometabolic Health; Council on Clinical Cardiology; Council on Epidemiology and Prevention; Council on Cardiovascular and Stroke Nursing; Council on Functional Genomics and Translational Biology; Stroke Council. Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign: a scientific statement from the American Heart Association. Circulation. 2016;134(24):e653-e99. 3. Gitt AK, Wasserman K, Kilkowski C, Kleemann T, Kilkowski A, Bangert M, et al. Exercise anaerobic threshold and ventilatory efficiency identify heart failure patients for high risk of early death. Circulation. 2002;106(24):3079-84. 4. Edwards AM, Clark N, Macfadyen AM. Lactate and ventilatory thresholds reflect the training status of professional soccer players where maximum aerobic power is unchanged. J Sports Sci Med. 2003;2(1):23-9. 5. Hoff J. Training and testing physical capacities for elite soccer players. J Sports Sci. 2005;23(6):573-82. 6. Midgley AW, McNaughton LR, Jones AM. Training to enhance the physiological determinants of long-distance running performance: can valid recommendations be given to runners and coaches based on current scientific knowledge? Sports Med. 2007;37(10):857-80. Erratum in: Sports Med. 2007;37(11):1000. References