Cardarine GW and Andarine S4 are the best option hands down. Cardarine will greatly enhance your endurance, cardrio and recovery. You will also lose fat with it, and even gain lean mass. S4 will give a great boost in strength, so you will have the opportunity to workout harder without gaining any mass. After the cycle run a mini-PCT of clomid, nolva, and Ostarine MK-2866.