I'm not sure I understand everything. So fats breaks down to acid and then converts to carbs for muscle use if heart rate is higher? Would consuming more carbs (as food) help muscle recovery?
Simplified, Carbs are an energy source to feed the muscle, there are simple carbs Sugar sweets cake etc and complex carbs which are slow release porridge, bananas etc, the body stores around 400g of carbs for instant use (90mins ish exercise) anything over 400g is turned to fat, you can intake carbs as you exercise which help replenishes the body store providing you are not exerting yourself in high rate zones, there is a heart zone which is fat burning, the heart rate is not too high and the body can break down the fats and turn it into carbs and the body can sustain this for hours in a leisurely ride out, when you are exercising you will have varying amounts of muscle damage depending on how you push yourself, while carbs feed the muscles with energy, if you are exerting yourself in a high HR zone then lactic acid is fed into the muscle instead of carbs as the body cannot produce the carbs fast enough, the acid is an irritant to the muscle and slows down recovery. Proteins build and repair muscles, post ride is when you consume protein meats fish protein shakes etc. Assuming we have got the heart rate down and burnt off the lactic acid, we arrive home, after around 30mins of stopping the body will want to start repairing the muscles (this is why if you stop too long you get a bit stiff and it takes a bit of getting back into it) this is when the proteins come in to action, muscles contract when they are in the repair stage ( your legs go all stiff) the worse thing you can do is have a hot bath as this relaxes and expands the muscles and does more damage, being cold contracts the muscles and speeds up recovery, this is why the pro's sit in baths of ice, you could shower your legs in cold water and this will help contract muscles and aid the repair. it is hard to explain it as there is a lot of variables, but, I hope you get the gist of it.