Maximum oxygen intake and maximum heart rate during strenuous work

¹ Applied Physiology Laboratory and Mathematical-Statistical Division of the Transvaal and Orange Free State Chamber of Mines, Johannesburg, South Africa

At least five separate determinations were made of oxygen intake and heart rates at various levels of work on a bicycle ergometer, up to and above the maximum level of O₂ intake of four highly trained men. From these measurements it has been possible to fit appropriate curves to the experimental data and test for their goodness of fit. At low rates of work a straight line fits both O₂ intake and heart rate plots against work rate, but at high work rates the curves tend toward an asymptote. The O₂ intake curve reaches its asymptote more slowly than does the heart rate; hence, if heart rate is plotted against O₂ intake and a straight line fitted and extrapolated to the maximum value of heart rate, the O₂ intake at this value is an underestimate of the actual measured maximum O₂ intake. Because of the characteristic slope of the best-fit curve of oxygen intake against work rate, the criteria proposed by some earlier investigators for the level of O₂ intake at which the maximum is unequivocally attained, is open to criticism. An alternative is proposed. The maximum levels of O₂ intake and maximum heart rate of trained men studied over 4 months is remarkably constant, having average coefficients of variation of 4.3% and 3.5%, respectively.