Nike InfinityRN 4 First Impressions: A Real Update to Nike's Supportive Daily Trainer

Introduction

The Nike InfinityRN 4 is the first genuine update to the Infinity line in a while. The previous three versions were mostly minor upper tweaks, while the original formula stayed the same: a stability and support shoe that skips traditional posting in favor of a wider base and softer foam.

After the first runs in it, the early verdict is positive. This is a supportive daily trainer that pampers the foot, and it may be worth a look if you want cushioning with a bit of structure.

What’s New in the Nike InfinityRN 4

The headline change is ReactX, a new Nike foam that is designed to be more sustainable and more responsive than before. Sustainability claims sometimes come with a performance trade-off, but early miles suggest that is not the case here. One tester put 22 miles on the shoe within the first two days and found it supportive throughout, with the arch support proving especially welcome while managing a mildly bothersome achilles.

ReactX Foam: Dense but Bouncy

ReactX is not a super-soft foam. It feels dense, yet still bouncy, and the tuning lands in a sweet spot: cushioned enough for easy days, responsive enough to keep runs feeling lively. Combined with the supportive arch, feet felt good both during and after runs.

Sizing and Fit: Snug Knit, Go Half a Size Up

The knit upper is very stretchy and runs snug, especially near the front of the foot. One tester recommended going up half a size because it felt too tight in normal sizing. Nike itself recommends going up half a size from your usual fit.

That said, not everyone needs the adjustment. A snug knit can be a good thing: stretchy uppers that expand too much sometimes feel clunky, and a secure wrap keeps the ride locked in. One tester stayed with normal sizing and was happy with the closer fit.

Ride Feel: Heavy on Paper, Light on the Road

Here is the surprising part: the InfinityRN 4 is heavy, but it does not feel heavy out on the road. On the scale, this would normally be a deal-breaker, yet on foot the shoe simply rides nicely.

With about 10 miles logged, it is already working well as a daily trainer. It is soft enough to double as a recovery run shoe, and the support gives it a genuinely pampering feel underfoot.

Buying Advice

Go up half a size unless you prefer a very snug knit, and expect a shoe that rides lighter than its spec sheet suggests. If you want a supportive, cushioned daily trainer for easy miles and recovery days, the ReactX update makes this the most interesting Infinity in years.

Conclusion

The Nike InfinityRN 4 is a real step forward for the line: a new more sustainable and responsive foam, strong arch support, and a ride that belies its weight. The snug knit upper and heft are the trade-offs, but early miles point to a very likable supportive daily trainer.