I did the radio tower again yesterday, but again had to lower the difficulty setting otherwise I wouldn't have made it. I look at my current results at 25% difficulty doing it vs. what I did 4-5 years ago at 50% though and it is still the same number of calories and calories are a fixed factor back to joules, which is watts x seconds. I may average fewer watts now, and it takes more time, but it is still the same amount of work. Somewhere in there though is a human efficiency factor, and is it more efficient to stand and grind or to spin? All the formulas just use 25% for that. As a spinner do I make better use of my output since I don't lose momentum with each chomp on the pedal at the bottom of the stroke? Ah, maybe. But if you want to spin you just get a smaller front ring or larger rear cog or both in real life.