The old adage is true: keep the Mammut T Aenergy High GTX Boot close, and keep your energy bars closer. As your body becomes more and more fatigued at higher and higher elevations, those energy bars seem to dull the aches and pains while you give your lungs a chance to catch up, but you'll notice that your feet are ready for a few more miles. That's because T Aenergy was built for the most demanding trails, with Mammut's Rolling Concept for a cushy, casual stride over rocks and around tree roots. Gore-Tex Performance Comfort amplifies the waterproof membrane's breathability for performance-driven comfort, and Vibram's rubber comes with a Scale tread for extra traction on slippery surfaces.