Does anyone else do this?
I tried it out recently and think it's been helping me go longer, harder and recover faster. My protein shake basically consists of the classic 4:1 carb to protein mix, with maltodextrin and dextrose making up the carbs and whey making up the protein with a little L-Glutamine and BCAA's (they come stock in my powder). There's good evidence that BCAA's during endurance exercise is good... I think I'm getting at something similar by doing whey as well. I know the maltodextrin is probably doing the majority of good but it seems to make sense that having some amino acids shuttled to the muscles as well as carbohydrates would be good stuff to have in your system right in between sets of hard intervals or climbs. I've been doing this during tempo rides and intervals so far with good results, and still drink another protein shake afterwards (though a smaller one than when I was just doing all my protein/carb post-workout).
I still eat a Clif bar about 45 minutes into a long tempo ride, and then cycle in the shake later on. Before I was doing this, I was mainly just eating Clif bars, bananas and PBJ's on my rides, and sometimes honey from a Hammer flask.