Sermorelin[FONT=arial, sans-serif] Acetate, also known as GRF 1-29, is a Growth Hormone Releasing Hormone (GHRH). The problem with peptides if finding a legitimate source. The market is full of fakes. A lot of my clients have gotten really weird rashes and lumps when they used peptides against my advice.
Even if you could find a legitimate source, Sermorelin will cause a lot of water retention which is the last thing you want for endurance.
Your best option is cardarine -> [/FONT]http://www.evolutionary.org/cardarine/
Cardarine will directly increase fat loss and endurance with no side effects. It isn't a hormone or a stimulant so there is no risks of hormone suppression, water retention or cortisol increases.