I've used it during every cycle for the past 10 years at 20mg per day without issues. Excellent endurance and excellent results when it come to lipids. As everyone knows Tren can kill cardio, but on Cardarine I pushed through 1 hour of treadmill without an issue. My cholestrol is 170 range while on it. With that said I also have a clean diet and do cardio religiously. Personally I don't run a cycle with out it. I've done two detailed logs with my results.