consider there might only be a small shift. Couzens references this 1992 Coyle/Joyner article: Endurance exercise performance: the physiology of champions - PMC and I couldn’t find the full article. However the following year Coyle published this article: Cycling efficiency is related to the percentage of type I muscle fibers - PubMed and I did find a PDF of it. Paraphrasing the summary:
- two groups of cyclists
- group 1 had 73% type 1 muscle fibers in legs
- group 2 had 48% type 1 muscle fibers in legs
- during 1 hour test, group 1 generated 9% more power at same energy cost as group 2
And from page 1:
- We conclude that a high percentage of Type I muscle fibers improves endurance performance ability by significantly increasing the power output generated for a given rate of oxygen consumption and energy expenditure.
Hope that helps.