The problem with steroids is that they will negatively impact endurance and most steroids will also cause a lot of water retention and increases in body weight. Steroids really aren't optimal for athletes. They will increase strength and recovery, yes, but they will negatively impact endurance and the increase in body weight which will slow you down.
I would forgo steroids all together and use SARMS instead. SARMS will directly increase endurance, fat loss, recovery and lean muscle mass with no increases in body weight or water retention. You won't get the same strength increase from SARMS that you would with steroids, but you get all the benefits with none of the side effects. They are also extremely minimal in the way of side effects and legal to use.
I suggest running the SARMS triple stack. It is comprised of S4, ostarine and cardarine.
S4 will increase lean muscle and strength
ostarine is the best SARM for recovery
cardarine is the best SARM for fat loss
You get the best of everything that way
Run the triple stack as outlined in this article here:
http://www.evolutionary.org/the-SARMS-triple-stack-protocol
After the triple stack, run a mini PCT. 4 weeks of the following:
clomid at 25mg/day
nolvadex at 20mg/day
HCGenerate ES at 5 capsules/day
n2guard at 3 capsules/day
SARMS are minimally suppressive, there is no risk of aromatization (therefore no estrogen related side effects) and legal to use. You can get everything you need off sarms1.com, n2bm.com and ag-guys.com