5 field-tested, natural fitness enhancers5 field-tested, natural fitness enhancers

Participation has skyrocketed in ultra-endurance activities like Tough Mudder, Spartan Race, IronMan and marathons nationwide and with it, the desire for natural fitness enhancers. We test-drove a few of these energizers on a particularly arduous bike ride. Read how they stacked up so you know what to stock.