Delta efficiencies of running and cycling

Purpose: The purpose of the present study was to compare delta efficiencies of running with cycling, while several factors that can possibly influence delta efficiency were excluded. Methods: Twelve subjects performed a submaximal running and cycling test on subsequent days. Delta efficiencies of running and cycling were compared at equal metabolic intensities. Furthermore, rest periods were included in the protocol to avoid fatigue. Pedaling and stride frequencies were held constant during the tests. Finally, the influence of two ways of applying extra external load (inclination of treadmill and horizontal impeding forces) on the delta efficiency of running and cycling was investigated. Results: The results of the present study show that the mean delta efficiency of running (45.5%) is still significantly higher than the mean delta efficiency of cycling (25.7%). The way extra external load is applied does not influence delta efficiency. Conclusion: The way of loading and the difference in metabolic intensity can be excluded as causes for the observed difference in delta efficiency between running and cycling. It is suggested that a different contribution in the metabolic load attributable to muscular activity of the arms and/or trunk that does not directly contribute to the work needed to overcome the amount of applied external load may be a relevant factor.