I know this has probably beaten to death a bunch of times, but I spoke to my physiology professor, who is actually really smart and even ran track in college, about cns fatigue. His very first reaction was like what the heck are you talking about, thats baloney.
He says motor neurons can constantly fire all the time and have no fatiguing implications and that the only cns fatigue there could ever be would be exclusively related to motivation.
That if someone runs a full speed 100m one day, if a lot of variable things are controlled like muscular recovery, there’s no soreness, loss of motivation etc., then that person could absolutely repeat that same effort they did the day before with no loss of speed. That, physiologically, there is no conceivable thing like cns fatigue.
Now, I know from personal experience 3x a week high intensity is a lot better than doing it everyday or more than 3x a week, at most. But is he right? How can I respond?