I race TT’s against many who do and don’t use them.
Can’t say I’ve tried them but I’m pretty sure the benefits are minimal at best and probably more psychological as the fastest guys are just the fittest guys.
If they’re was a clear advantage in using them I’m sure the pros would all use them as stuff like this gets tested to death these days.
I’m pretty sure the likes of Martin and Sparticus don’t use them but Wiggo does.
I guess you pays your money.