The Impulse retains Altra's signature roomy toe box and zero-drop design, intended to encourage a more natural, low-impact footstrike, but the added stability should appeal to runners who haven't fully bought into the natural running hype. We found the ample toe box to be an initial relief to feet used to being squeezed. Be forewarned, however: Your feet may not quite know what to do with all that extra room. The added toe splay made us feel like our feet were working extra hard to grab at the ground, and we came home with a few blisters. This should neutralize over time, though, as your feet adjust to the setup. Meanwhile, the StabiliPod technology performed well in lateral motion—a nice bonus if you intend your shoes to work as hard in the gym as they do on the pavement.