where did u read that myth that juice improves endurance???!!! it certainly wasn't this board!
there are some guys who say they improved their endurance on juice, those are the guys who likely never ran before .. yeah if you never ran before and you juice and start running you will improve your endurance.. but guys who run a lot and run say a 6 minute mile which is very solid will see their times get crippled on juice.
i was running 45 miles a week.. sub 5 minute miles. 17 minute 5K's.. i took dbol and at half a mile my calf muscles felt like they were gonna explode. so i have no idea how you can improve your running when your calf turns into sand bags.
as a runner you should understand how max heart rate works and how that dictates your top line speed, now with juice your RBC count goes sky high. so you are pumping more blood in less time. hence your max heart rate will go down, which will cause your top line speed to go down. make sense?