On Sunday, Sebastian Sawe shattered the unofficial sub-2-hour marathon record in an official race. He did it wearing the latest version of Adidas’ top performance running shoe—the Adidas Adizero Adios Pro Evo 3 ($500).

This impossibly light, under-100-grams (3.5 ounces) carbon race shoe promises enhanced running economy, meaning it can cut the energy cost of pounding out miles. For Sawe, the Pro Evo 3 clearly delivered, but is it a sensible option for the rest of us chasing marathon personal bests?

I was lucky enough to be one of the first to lace them up, taking them for a 5-kilometer treadmill test ahead of their launch at the London Marathon. Here are my first impressions on whether you should start saving.

Highs and Lows

When it comes to weight-saving running shoes, the Adidas Adizero Adios Pro Evo 3 sets a new low benchmark. At under 100 grams, it’s unfathomably light on the scales. It's easily the most featherweight shoe I've ever held, almost 150 grams lighter than the Nike Alphafly 3 ($305).

Every 100 grams cut from a shoe reduces the aerobic demand of running by 1 percent. That’s potentially important for record hunters (more on that in a moment).