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

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Morton (J Sport Sci 29:307–309, 2011) proposed a model of the peak power attained in ramp protocol (\(\dot{w}_{\text{peak}}\)) that included critical power (CP) and anaerobic capacity as constants, and mean ramp slope (S) as variable. Our hypothesis is that \(\dot{w}_{\text{peak}}\) 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 (\(\dot{V}{\text{O}}_{{ 2 {\text{max}}}}\)) and \(\dot{w}_{\text{peak}}\) 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.


\(\dot{V}{\text{O}}_{2\hbox{max} }\) was the same in all tests; \(\dot{w}_{\text{peak}}\) was significantly lower the longer the step duration, and all values differed from the maximal power of the Åstrand-type test (\(\dot{w}_{\hbox{max} }\)). 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 \(\dot{w}_{\text{peak}}\) is a protocol-dependent variable, the difference between \(\dot{w}_{\hbox{max} }\) and CP is a constant, so that their values do not depend on the protocol applied.

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a :

Whipp’s model constant equal to anaerobic work

b :

Whipp’s model constant equal to maximal mechanical aerobic power


Critical power


Heart rate


Incremental intermittent Åstrand-type test


Incremental stepwise ramp test

[La]b :

Blood lactate concentration


Respiratory exchange ratio

S :

Ramp slope

t :


T :

Time to exhaustion

T S :

Step duration

\(\dot{V}_{\text{Emax}}\) :

Maximal expired ventilation

\(\dot{V}{\text{O}}_{2}\) :

Oxygen consumption

\(\dot{V}{\text{O}}_{{ 2 {\text{max}}}}\) :

Maximal oxygen consumption

\(W'\) :

Morton’s model constant equal to the work carried out to sustain the power above critical power

W M :

Total mechanical work

\(\dot{w}\) :


\(\dot{w}_{\hbox{max} }\) :

Maximal aerobic mechanical power

\(\dot{w}_{\text{peak}}\) :

Peak power of a ramp test


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The authors thank all the volunteers who participated in this study. This research was supported by the Swiss National Science Foundation Grant 32003B_127620 to G. Ferretti.

The authors declare that they have no conflict of interest.

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Correspondence to Alessandra Adami.

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Communicated by Jean-René Lacour.

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Adami, A., Sivieri, A., Moia, C. et al. Effects of step duration in incremental ramp protocols on peak power and maximal oxygen consumption. Eur J Appl Physiol 113, 2647–2653 (2013).

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