Nike InfinityRN 4 Review: A Heavy, Rockered Daily Trainer with Mild Guidance

Introduction

The Nike InfinityRN 4 is Nike’s maximal daily training shoe, and if you have run in the Infinity Run series before, be prepared: this version is completely different. It keeps the same ongoing question of whether it counts as a stability shoe, which Nike argues for and many would argue somewhat against compared to earlier shoes in the line. Fans of version three should note that Nike changed the formula again. It is not bad, it is just really different.

Specs at a Glance

A men’s size 9 weighs 11.1 ounces and a women’s size 8 comes in at 9.4 ounces. The stack measures 39 millimeters in the heel and 30 in the forefoot for a nine millimeter drop, with full-length Nike React X foam. The React X midsole is slightly firmer than expected, and the completely new knit upper fits a half size small.

That fit note is the single most important thing to know about this shoe: do not go true to size. You will need to go half a size up. The upper sits very low over the toes but feels very secure, so if you like a compression-sock feeling, this delivers. The midfoot and the gusseted tongue lock the foot down very compressively. That tight first impression is not narrow so much as low, and it can ease as the upper relaxes with wear.

Upper and Fit

People with higher-volume feet may need to wait for the stretch, or this may simply not be a good option. People with lower-volume feet are likely to really enjoy the secure, compressive feel.

There is also a flexible heel counter at the back, which is good news for runners with heel sensitivity. It did not cause any irritation, which is a genuine plus in this category.

Ride and Performance

This is a heavy shoe, and it is very difficult to pick up the pace in unless you are significantly stronger than the average runner. The ride is rockered, and there is not much bounce in the midsole. React X here is compliant rather than resilient: the foam compresses, and you roll forward instead of getting energy returned. There is a little flexibility in the forefoot, but the overall platform is maximal and stiff, especially through the heel, with a small posterior flare and a rocker profile.

Once you settle into a rhythm, the ride is fine for easy miles. Just do not try to pick up the pace in this one.

Stability Features

The stability approach is arguably better executed than the previous version. Instead of the plastic elements that could feel irritating, the InfinityRN 4 uses full-length sidewalls integrated directly into the sole.

The medial side of the sole is filled in, while the lateral side has a structure that can collapse inward if you land really far lateral. For runners who land aggressively on the lateral edge, this is actually a mild guidance shoe with a lateral bias: if your foot drifts too far laterally, the sole responds to guide it back. It is not in-your-face stability; it is very well integrated. Be aware, though, that for some very lateral-landing runners this could feel like a struggle shoe.

Overall, think of it as a maximal daily trainer with mild guidance rather than a dedicated stability workhorse.

Who Should (and Shouldn’t) Buy the InfinityRN 4

The InfinityRN 4 suits runners who want a max-cushion, rockered shoe for easy daily miles and are okay with a heavier weight. The compressive knit upper rewards low-volume feet, the half-size-up fit rule is non-negotiable, and the integrated sidewalls offer gentle guidance without the irritation of older plastic-based systems.

If you want a lighter shoe for tempo runs, or if you have high-volume feet and dislike a tight, low-fit upper, look elsewhere. If easy, cushioned, guided miles are the goal, this is a solid option to consider.

Conclusion

The Nike InfinityRN 4 is a heavy, rockered maximal trainer with a firmer-than-expected React X midsole, a compressive knit upper that runs half a size small, and a well-integrated mild guidance system built into the sole. It is built for easy miles, not pace work, and runners who match its fit and ride character will find a lot to like.