How did A V Hill understand the VO2max and the "plateau phenomenon"? Still no clarity?

A recent editorial in Medicine and Science in Sports and Exercise concludes that the study of Hawkins and colleagues confirms "beyond any doubt the proposition of Hill and Lupton". It is not clear which of Hill and Lupton's propositions have been proved "beyond any doubt".

A review of all the relevant publications of A V Hill and his colleagues.

Hill and Lupton believed (i) that myocardial ischaemia limits maximal exercise performance by inducing circulatory failure; (ii) that a "governor" protects the ischaemic heart by causing a "slowing of the circulation" during maximal exercise; (iii) that the oxygen cost of running increases exponentially at speeds above 16 km per hour; and (iv) that humans reach their highest measurable oxygen consumption of about 4 litres per minute at that running speed. Hill and Lupton neither invented the concept of the "plateau phenomenon" nor utilised this concept to establish that a "true" maximum oxygen consumption (VO2max) had been achieved. Nor did they measure cardiac output during exercise.

Accepting uncritically this modern interpretation of Hill and Lupton's theory that the cardiac output limits maximal exercise performance whether or not the plateau phenomenon is present fails to answer the question first posed more than 20 years ago: What causes the termination of exercise when the "true" VO2max is achieved without the "plateau phenomenon"? According to the Hill and Lupton model, this cannot be because a limiting cardiac output has been reached. Since a majority of maximal exercise tests terminate in the absence of the "plateau phenomenon", this is seemingly an important question.