RAX is the root of the Old English word "raxan," meaning "to stretch." MAX is slang for "maximum." Combined, RAXMAX literally means maximum stretching, and conjures up notions of expansion, flexibility, and durability. It can easily be applicable to a wide range of businesses: manufacturers and distributors of various types of stretchable clothing, outdoor sports (eg, bungee jumping, trampolines, base jumping), and fitness products and services (eg, gyms, fitness equipment, personal trainers).
RAXMAX.COM is a great and brandable domain name, very short, only 6 letters. Easy to spell and easy to remember.