With the design closest to traditional in Newton’s lineup, the Sir Isaac (Men's) and the Lady Isaac (Women's) are a stepping-stone for runners looking to transition from a typical trainer to other Newton models.
Newton shoes are built around the concept of promoting a forefoot strike when running. Their shoes feature low drop platforms, as well as forefoot lugs on the outsole to increase cushioning and responsiveness under the metatarsal heads.
The Sir Isaac serves as the entry point to Newton’s lineup, bridging the gap between a traditional trainer and the company’s lower profile and lighter offerings. With a 4mm offset (relatively high compared to other Newton models) the transition from a traditional geometry to the Sir Isaac is easier. Still, runners used to a 10+mm offset will need to ease into the lower offset experience gradually, adding miles over a span of weeks.
Though the upper is not the main selling point of the Sir Isaac, we were impressed with the fit it provided. The forefoot is moderately roomy and can accommodate most foot shapes. We found the heel cup to hug the rear of the foot closely enough to prevent any slippage, and the well-placed overlays provided a secure feeling without any drama or irritations.
For testers without prior experience in Newtons, the Sir Isaac provided a run that took some getting used to. The shoe isn’t made for anything other than forefoot striking – striking anywhere but directly on the lugs was possible but incredibly clunky and awkward. We didn’t notice a significant amount of additional cushioning from the lugs, though they do cause the runner to roll forward, delivering a small push to toe-off for a more energetic run. In all, though this shoe may not be for everyone, those waiting to develop a forefoot running strike may want to look into the Sir Isaac as a tool to assist in their transition.
The forefoot actuator lugs felt pretty awkward for the first few runs. They definitely promote a forefoot strike - anything else results in an awkward ride.
As Newton says, ease into this shoe if you're new to mid-to-forefoot striking to reduce the strain on your lower legs.
The upper is my favorite part of this shoe. No bells and whistles that you don’t need, overlays right where they should be, and a fit that is spot on.