Newton Sir Isaac
For access to all of our training, gear, and race coverage, plus exclusive training plans, FinisherPix photos, event discounts, and GPS apps, sign up for Outside+.
A guidance trainer with a racing flat feel and one that encourages better running form sounds like too much to ask from a shoe but, depending on foot shape and biomechanics, the Sir Isaac delivers it all. It tested light and snug and required a break-in period to get used to hitting a bouncy spot. Forefoot strikers were pushed toward their toes while midfoot runners felt they were running more toward the heel.
Heel fit: Super snug
Midfoot fit: Super close-fitting
Forefoot fit: Narrow
Flexibility: Stiff
Perceived Weight: Light
Barefoot factor: Structured
Cushioning: Somewhat firm
Stability: Very stable
Responsiveness: Bouncy
New to the Fit, Feel & Ride Shoe Guide? Click here to learn how it works.
