Endurance gains in muscle are a result of increasing the number of mitochondria, and how well they can completely use and process oxygen+fuel. Think of mitochondria as “engines”
Strength training involves increases in muscle size / cross-sectional area, neural muscular coordination, and maximal force production.
Back on endurance, there are studies looking at adaptation froms three types of training:
- endurance rides or “long steady distance” (LSD)
- HIIT or high-intensity interval training
- SIT or sprint interval training
Here is a view of each and leg muscle adaptations:
