However, a major role of the cardiorespiratory system for VO SB 2 sb max is now undisputed, if large muscle groups are involved during intense exercise (e.g. 2-legged pedaling).[3] Nowadays, VO SB 2 sb max is among the most assessed parameters in sports medicine. The year 2023 marks the 100th anniversary of the "maximum oxygen intake" (VO SB 2 sb max), first described by Hill and Lupton in the I QJM i in 1923.[1] These authors suggested an upper limit to oxygen intake depending on the capability of the cardiorespiratory system to deliver inspired oxygen to the working muscles. Since then, whether the cardiorespiratory system (oxygen delivery), the exercising muscles (capillarization and mitochondrial oxidative capacity), and/or regulation by the central nervous system primarily limit VO SB 2 sb max has been heavily debated.[2] In fact, this remains to be unambiguously clarified even today. [Extracted from the article]