I've searched some threads but wanted to ask if anyone had any specifc recommendations for supplements, pre-workout blends etc, to aid endurance while playing 1.5 - 2 hours of racquetball / squash.

Somedays my cardio feels pretty good, but then I have days like today, that for some reason, during the middle of my third game I was so gassed I could barely lift my racket. My legs were also on fire and I felt I was playing with ankle weights on.

I eat a very low carb diet in general and wonder if that isn't negatively affecting my performance?

I tend to shy away from fast digesting carbs for health reasons - avoiding insulin resistance, fat storage, etc - are there any good pre-workout blends with primarily slow-digesting carbs?