For races which are long enough that the average speed falls below the maximum speed achievable via a 'walking' style of movement, is it more energy efficient to 'walk' at that speed as opposed to running at that speed?
If not, are there any references available as to why a running style is preferred? Many sites state that running consumes more calories than walking the same distance, which would suggest that it is, in that sense, less efficient.
To summarize the study posted by ColonelFazackerley, more efficient only if your marathon speed is below the normal crossover speed between walking and running.
Eight competitive racewalkers were studied to determine a) the speed where running and racewalking become equally efficient, b) if, at a similar VO2, the physiologic responses to submaximal exercise differ between running and racewalking, and c) if VO2 max can be attained during racewalking. The speed at which running and racewalking elicited the same VO2 (approximately 30 ml X kg-1 X min-1) was between 8 and 9 km X h-1. Racewalking was more efficient at slower speeds, and running was more efficient at faster velocities. When running and racewalking were compared at similar oxygen consumptions, heart rate, ventilation, perceived exertion, and respiratory exchange ratio responses were identical. During maximal exercise, running and racewalking resulted in a similar VO2 max (60.4 +/- 1.3 vs. 58.1 +/- 1.5 ml X kg-1 X min-1), heart rate (193 +/- 4 vs. 188 +/- 4 bpm), ventilation (130.6 +/- 5.9 vs. 126.3 +/- 6.6 l X min-1), and post-exercise blood lactic acid concentration (9.8 +/- 0.6 vs. 9.6 +/- 0.7 mM). These results indicate that the speed where racewalking and running become equally efficient is similar to the crossover speed for conventional walking and running. Cardiovascular, respiratory, and perceptual responses during running and racewalking are the same during maximal exercise and during submaximal exercise at the same VO2.
