Rachel did not need long to work out what kind of shoe the adidas Prime X 3 Strung wanted to be. Over 100km of long runs, recovery days and steady aerobic miles, the pattern stayed the same. This is a high-stack super trainer built to make tired legs feel better, not a stripped-back racer built to punish every lazy step.

The headline is simple. The Prime X 3 Strung still looks huge, still sits exceptionally tall underfoot, and still carries all the visual drama that has defined the line. But on the run, it feels calmer than before. Smoother. More controlled. Less like you are trying to manage the shoe, more like the shoe is helping manage the run.

That matters, because a shoe this tall only really works when the cushioning and bounce come with enough stability to trust over distance. Rachel's verdict after 100km is that adidas has got closer to that balance here. The Prime X 3 Strung feels lighter and more connected than the previous version, with a ride that holds together particularly well on easy runs, recovery days and long sessions where protection matters more than outright speed.

The adidas Prime X 3 Strung's role

High-stack super trainers have carved out a clear role in modern running. They bring race-day foam, rocker geometry and plenty of protection into everyday training, especially the sessions that tend to leave the deepest mark on your legs. They are not built to replace a daily trainer for every kind of run. They are there for the miles that stack up, the long road sessions that drag on, and the recovery days where you still want some life underfoot without beating yourself up.

That is where the adidas Prime X 3 Strung makes the most sense. It is not really trying to be an all-rounder. It is trying to make distance feel smoother and less punishing.

Fit and comfort

Rachel wore her usual UK 5 and found the fit true to size. More importantly, it stayed secure over distance. In a shoe with this much stack, any slipping or heel movement becomes a bigger issue than it would in a lower, more traditional trainer. That never became a problem here.

The Strung upper is one of the strongest parts of the shoe. It wraps the foot closely without feeling restrictive, giving enough structure through the midfoot while staying comfortable over longer runs. Rachel reported no rubbing, no irritation and no real hot spots, even once the mileage started to build. The forefoot also feels a touch roomier and more relaxed than the previous version, which is useful on longer sessions when feet naturally start to swell.

Breathability held up well too, which matters in a shoe designed for extended time on foot. A high-cushion trainer can quickly become hard work if the upper traps heat, but that was not the case here.

Ride feel

The word Rachel kept coming back to was smooth, and that tells you plenty about how the Prime X 3 Strung runs. The combination of a high-volume Lightstrike Pro midsole and aggressive rocker geometry gives it a rolling, forward-moving feel that makes transitions easier than you would expect from a shoe this substantial.

It does not feel sharp in the way a race shoe does. It feels efficient. Each step feeds the next without asking much from you, which is exactly what you want on days when the goal is to keep moving well rather than chase pace.

Just as important, the ride stays controlled. With super trainers, that is the line manufacturers often struggle to hit. Plenty of bounce is easy. Bounce you can actually trust at the end of a long run is much harder. Rachel found the Prime X 3 Strung soft and lively, but not vague or sloppy under load.

Long runs and marathon training

This is where the shoe earns its place. Long runs expose every weakness in a trainer, especially once fatigue starts to change your mechanics. Rachel found that the Prime X 3 Strung stayed stable and consistent late into double-digit mileage, which is exactly what you want from a shoe built around protection.

The triple-layer Lightstrike Pro setup, supported by a carbon plate and Energy Rods 2.0, gives the shoe plenty of rebound without tipping into chaos. The heel feels springy without feeling unstable, and the forefoot rolls through cleanly once your stride starts to shorten. The result is a shoe that still feels composed when your legs are doing less of the work for you.

That is the real appeal here. Not the first few fresh miles, but the later stages of a long run when you want the shoe to help you stay organised.

Can you run fast in it?

Yes, to a point. Rachel found there was still enough life in the midsole to respond when she picked the pace up, and the rocker shape keeps working even when the effort rises. But speed is not the main reason to buy this shoe.

The adidas Prime X 3 Strung is still a big, protective trainer first. It can cover tempo work if comfort is your priority, but runners looking for something light, sharp and race-focused will find better options elsewhere in the adidas line. This is a shoe that helps you preserve your legs, not one that turns every faster session into a personal best attempt.

Stability

For a shoe this tall, stability is the question. Rachel's verdict was positive. The wider forefoot platform and more planted heel make the Prime X 3 Strung feel more balanced than previous versions, and that change is one of the most important improvements.

It still does not feel low, direct or especially close to the ground. It is not meant to. But it feels more predictable than some super trainers in this category, which makes a difference on real roads, with corners, cambers and all the small inconsistencies that can make high-stack shoes feel awkward.

The balance adidas has found here is probably the biggest reason this version feels more usable day to day.

Outsole and grip

The outsole uses Continental rubber in the forefoot and Lighttraxion through the heel, and Rachel found grip reliable across dry and damp roads over the full 100km test. That included cornering, descents and the kind of slightly slick early-morning surfaces that quickly expose weak rubber.

Grip is not the glamorous part of a shoe like this, but it matters. A super trainer only works if you trust it when the road is less than perfect. Rachel did.

Durability after 100km

After 100km, the shoe had kept its bounce well and the ride still felt consistent. That is encouraging, because super trainers can sometimes feel brilliant early on and then lose some of their character once the mileage builds. Rachel's experience suggests the Prime X 3 Strung holds onto its identity well enough to justify a place in a marathon block rotation.

It is best suited to roads and smooth pavement, though it can handle dry park paths if needed. Uneven surfaces are not really the point here.

Who the adidas Prime X 3 Strung is for

This is a strong option for runners who want maximum cushioning and a smooth, protective ride for long runs, recovery days and steady aerobic mileage. It makes most sense for runners who value comfort, flow and fatigue management more than ground feel or precision.

It makes less sense if you prefer lower-stack shoes, want a firmer and more direct ride, or need a lightweight option for faster workouts and race day.

adidas Prime X 3 Strung vs Prime X 2

Rachel's testing points to three clear gains over the previous version: better stability, smoother transitions and a ride that feels easier to trust over distance. The Prime X 2 had plenty of drama and bounce, but it could feel unruly. The Prime X 3 Strung keeps the same big-shoe identity while bringing more control to it.

That makes it a better long-run shoe, and probably a better real-world training shoe too.

Verdict

After 100km, the adidas Prime X 3 Strung feels like a more mature version of a bold idea. It is still tall, still visually extreme and still built around a huge amount of foam, but the ride is smoother, calmer and easier to trust than before.

For Rachel, that made it the shoe she kept reaching for when the legs were tired but the miles still mattered. That is the clearest endorsement a long-run shoe can get. Not that it makes you feel spectacular, but that it makes the work feel manageable enough to come back and do it again.