Effects of step duration in incremental ramp protocols on peak power and maximal oxygen consumption

Morton (J Sport Sci 29:307-309, 2011) proposed a model of the peak power attained in ramp protocol ([Formula: see text]) that included critical power (CP) and anaerobic capacity as constants, and mean ramp slope (S) as variable. Our hypothesis is that [Formula: see text] depends only on S, so that Morton's model should be applicable in all types of ramps. The aim of this study was to test this hypothesis by validating Morton's model using stepwise ramp tests with invariant step increment and increasing step duration.

Sixteen men performed six ramp tests with 25 W increments. Step duration was: 15, 30, 60, 90, 120 and 180 s. Maximal oxygen consumption ([Formula: see text]) and [Formula: see text] were identified as the highest values reached during each test. An Åstrand-type test was also performed. We measured oxygen consumption and ventilatory variables, together with lactate and heart rate.

[Formula: see text] was the same in all tests; [Formula: see text] was significantly lower the longer the step duration, and all values differed from the maximal power of the Åstrand-type test ([Formula: see text]). Morton's model yielded an excellent fitting, with mean CP equal to 198.08 ± 37.46 W and anaerobic capacity equal to 16.82 ± 5.69 kJ.

Morton's model is a good descriptor of the mechanics of ramp tests. Further developments of Morton's model demonstrated that, whereas [Formula: see text] is a protocol-dependent variable, the difference between [Formula: see text] and CP is a constant, so that their values do not depend on the protocol applied.