Boost and Lightstrike: two adidas foams, two different jobs
One is built from fused capsules of expanded TPU and returns more energy than almost anything else on the market. The other is EVA-based, lighter and firmer. They share a brand and a place in the shoe, and almost nothing else.
Two foams pulling in opposite directions
Both are adidas, both sit in the same part of the shoe, and they are built for different runs. Boost gives back more of the energy you put into it than almost any other foam, and it barely notices the cold – it is also the heavier of the two. Lightstrike is lighter and firmer and gets out of the way. Neither is the better foam. The question is which run you are buying it for.
What Boost is, and why it looks like that
Boost is not poured as a single block. It is moulded from small capsules of expanded thermoplastic polyurethane – E-TPU – fused together in the mould, which is why a cut-open Boost midsole looks like a bag of tiny welded beads rather than a slab of foam.
The material is made by BASF, which sells it as Infinergy and dates its arrival in running shoes to 2013, the year adidas launched Boost. BASF publishes figures for its performance grades: a rebound of over 75 on the pendulum test, and a midsole density of roughly 80 to 150 grams per litre.
Both numbers want a caveat, and the caveat is the useful part. The rebound is measured on the material, not on a shoe: something dropped on a slab in a laboratory comes back high, which tells you the foam is springy but not how much of that survives a foot, a sock, an outsole and a stride. And the density is exactly why Boost feels substantial underfoot. A foam that returns a lot by being dense is a foam you carry for the whole run.
The cold argument, which matters more here
Most midsole foam is EVA, and EVA stiffens as the temperature falls. A shoe that felt right in September feels like a board on a January morning, and a part of the cushioning you paid for is simply not there while it is cold.
E-TPU holds its properties far better across the range. adidas made a good deal of this when Boost launched, and it is the claim that has aged best – because in Britain it is not a marginal case. A large share of the running year here happens in months where a stiffened sole is the normal condition rather than the exception.
It is also the one argument for Boost that a lighter foam cannot answer by being lighter.
What Lightstrike is
Lightstrike is adidas’s EVA-based answer to its own foam being heavy. It is lighter and firmer, and it is what you will find under the shoes the brand builds for pace rather than for hours.
One distinction is worth holding on to, because the shared name hides it: Lightstrike and Lightstrike Pro are not the same foam. Lightstrike is the everyday workhorse. Lightstrike Pro is the softer, livelier racing version, and it appears in the Adizero line alongside a plate rather than on its own. Reading a review of one as though it described the other is the commonest mistake made about either.
Which one you actually want
If most of your running is long and easy, and a good deal of it happens in the dark and the wet, Boost is the one that earns its weight. The return is real at any pace, and the cold resistance is worth more in this country than the marketing manages to say.
If your running is shorter and quicker, or if you notice weight on your feet, Lightstrike does the job with less to carry. The firmness that reads as harsh on a slow hour reads as responsive on a session.
What neither foam does is make you faster for nothing. Energy return is the fraction of the work you already did that comes back, so a foam that returns more is a foam that wastes less – which is worth having, and is not an engine. If a shoe feels fast, the foam is one of four or five reasons, and the others are the geometry, the weight, the fit and the legs.
Where you’ll find it
Shoes on this site built on one of the two foams. They are examples of what each does in practice, not a catalogue.
Similar and competing technologies
Every midsole foam is a trade between how much comes back, how much it weighs, and how long it lasts. No material has won all three.
| Material | How it works | What it trades |
|---|---|---|
| Expanded TPU · Boost | Springy capsules fused into a block; the cell structure stores and releases the load. | The most reliable return and the best behaviour in the cold – for weight. |
| EVA and EVA blends · Lightstrike and most foams | The industry standard: light, cheap, predictable, easy to tune firm or soft. | Stiffens in the cold and packs down with the miles. |
| Nitrogen-blown foam · NITRO, DNA Loft v3 | Gas is forced into the foam to cut weight without losing softness. | Lighter than Boost at a similar softness; less comes back. |
| Supercritical foams · PEBA and blends, race shoes | A base polymer blown under pressure: the lightest and the liveliest of the lot. | Expensive, and finished in a few hundred miles rather than a few thousand. |
Both foams sit in the midsole, and how adidas arrived at them – a 1949 workshop, then Boost – is told in the story of the brand.