A team of pathophysiologists at the University of Milan has found that climbing stairs or walking for short bursts allows people to consume 20% to 60% more energy than if they do the same activity nonstop for the same distance. In their study, published in the Proceedings of the Royal Society B, the group asked volunteers to walk on a treadmill or climb stairs while also monitoring their oxygen intake.
I saw an interview with some exercise scientists talking about studies done on people who lived in rural less developed environments, think shepherds in developing countries. The studies indicated that while they may do 30,000 steps a day their body physiologically adapts and changes their movement paterns very quickly to use the absolute minimum amount of energy possible to move around. So their energy expenditure was more like what someone who walks 15,000 steps a day of stop start a day.
So, this is what cyclists do. Lots and lots of low intensity miles, to facilitate those adaptations, so that over time they put out the same power but at a much lower energy cost.
Conversely, those seeking to maintain high cardiovascular fitness must cross-train with a variety of exercises, to maintain the load on the heart a lungs .