So I've been doing morning cardio lately after a meal replacement shake (I can't eat breakfast and run). I'm not doing it on an empty stomach because my goal is endurance, not losing BF.

So my question is this. When I was doing AM cardio and trying to lose BF I would have my protein and flax shake PWO. But now that my goal is strictly muscle mass and endurance, what should my PWO cardio shake consist of? Just dextrose and protein? I can't eat a full meal for at least an hour after my cardio so please don't suggest that. Any ideas?