How to improve cycling mechanical efficiency?

Is there any specific training to improve cycling mechanical efficiency?

By cycling mechanical efficiency I mean the % of fuel burned in the body that gets converted into mechanical energy at the pedals. I’ve heard this can vary from 18-25%, which is a huge range. And a seemingly small improvement would have a sizable impact on FTP. For example, going from 20% to 21% would increase FTP by 5%.

I understand about minimizing unnecessary body motion on the bike, and I try focus on that on all of my training rides.

My interest lies more in improving the underlying efficiency with which muscles transform fuel to mechanical work. I find that I get and stay hot very easily when training, leading me to believe my efficiency is low - as most “wasted” energy is expended in the form of heat.

Anyone have experience trying to move the needle on cycling efficiency through training? Or maybe this just happens “naturally” as part of any cycling plan?