The Altra One2 (One-squared) is a wonderful blend of light weight and soft cushioning, and is a shoe I love to run in. In many ways it reminds me of the legendary Nike Mayfly, though it is not as light weight as that groundbreaking shoe. The One² is not as softly cushioned as a Minimax shoe, but it is a lot softer than the Saucony Virrata or the Mizuno Cursoris, and lighter the Adidas Energy Boost. However the One² does not last very long, making it an expensive shoe in terms of cost per mile. (I use The Science of Running Shoes as the basis of how I test running shoes and what you should look for in a running shoe.)

Altra One2 top	Altra One2 bottom	Altra One2 inside	Altra One2 outside

1 Characteristics

Why you’d buy it. It's a softly cushioned, lightweight show that's designed for a human foot. The Hoka Clifton is better cushioned, but a little heavier.
Cushioning . . The One²is softly cushioned, but because of its thinness it does not offer the same protection from rough ground that a true Minimax shoe would.
Drop. Like other Altra shoes, the One² is zero drop but with a slight rise under the arch. The One² tapers more gently from the ball of the foot to the front than most Altra shoes, mostly because it's so much thinner. The rear of the midsole is very slightly cut away to create a hint of a rocker.
Structure. This shoe uses single density of foam, but they are deep grooves cut into the bottom of the sole, and some shallower grooves in the top of the midsole. (These top cuts are hidden unless you dissect the shoe.)
Flexibility. The One² is a remarkably flexible for shoe due to the deep grooves in the bottom of the midsole, and the shallow grooves in the top.
Outsole. There is almost no outsole, just a couple of tiny patches of the extreme front and rear of the shoe. The bulk of the bottom of the shoe is exposed foam, which is part of the reason the shoe is so light as the harder rubber used on many shoes is quite heavy. However, this does dramatically reduce the wear characteristics, and I got only a little over 200 miles from mine before they needed retirement.
Shape. The shoe is the classic Altra shape, which follows the outline of the human foot much better than other makes. It has a broad toe box, but I find there is not enough height for my toes and I still have to cut the toe box open.
Upper. The upper is reasonably thin, but more substantial than you would expect from a shoe this light. It has excellent padding around the ankle opening.
Tongue. The One² has a classic tongue, but it's partially attached on one side to keep it positioned, which I like a lot. It has minimal but adequate padding.
Lacing. The flat laces work well and remained tied.
Heel Counter. The heel counter is quite soft, and comes as far up the back of the heel as is normal for running shoe.

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2 Cushioning and Shoes

It's intuitively obvious that the cushioning in a shoe will reduce the impact on your body when running. However, The Science of Running Shoes indicates that the reality is rather more complex. While slight cushioning may reduce the effort needed to run by improving your Running Economy, most scientific research indicates that more cushioning does further improve Running Economy. In addition, cushioning does not generally reduce impact and may actually increase it. This is counterintuitive, but is likely to be due to the way a runners mind and body adapts to softer cushioning. Unfortunately, the scientific evidence is far from complete and it's hard to give clear recommendations. I believe that some runners will prefer more cushioning, while others prefer less, and typically those running further have a fondness for greater cushioning. I also believe that a shoe should be as light as possible, and a shoe should justify its weight with the cushioning it provides. My advice is to decide what level of cushioning you're looking for, and then find the lightest shoes that also fit well and are comfortable.

3 Visualizing the Attributes of the Altra One2

How Altra One2 compares showing rearfoot cushioning against the performance penalty of its weight. Upper right is better.	How Altra One2 compares showing forefoot cushioning against the performance penalty of its weight. Upper right is better.
How Altra One2 compares showing the price against the benefit (cushioning/performance penalty). Upper left is better.	How Altra One2 compares showing the loaded drop against the benefit (cushioning/performance penalty). Upper left is better.

4 Comparisons

Here are some direct comparisons with its potential competition.

4.1 One2 and Hoka Clifton

Comparing the One² and the Hoka Clifton:

Similarities
- Both are top picks.
Advantage Altra One²
- Weight. The Altra One² is a lot lighter, but that lightness is due to less cushioning.
- Shape. The Altra One² has a much better toe box.
- Drop. The Altra One² is zero drop though the Clifton drop is smaller than a traditional shoe.
Advantage Hoka Clifton
- Cushioning . The Clifton has a lot thicker cushioning.
- Trails. The Clifton has a lot more protection on rocky trails.
- Longevity. Both shoes have a lot of exposed midsole, but the Clifton wears much better.

4.2 One2 and Saucony Virrata

Comparing the One² and Saucony Virrata:

Similarities
- Weight. Both are light weight.
- Flexibility. Both are extremely flexible.
- Drop. Both are zero drop.
- Outsole. Neither have much grip.
- Longevity. Neither last very long, with the exposed midsole wearing quickly enough to make the overall cost per mile quite high. (The Virrata lasts a little longer than the One².)
Advantage One²
- Cushioning . The One² is more softly cushioned.
- Shape. The One² has a much better toe box.
Advantage Saucony Virrata
- Price. The Virrata is often available at a lower price.
- Availability. The Virrata is easier to find, as Saucony is widely stocked.

Altra One2 top	Altra One2 bottom	Altra One2 inside	Altra One2 outside
Saucony Virrata top	Saucony Virrata bottom	Saucony Virrata inside	Saucony Virrata outside

4.3 One2 and Mizuno Cursoris

Comparing the One² and Mizuno Cursoris:

Similarities
- Weight. Both are light weight.
- Flexibility. Both are extremely flexible.
- Drop. Both are zero drop.
- Grip. Neither has much grip.
- Shape. Both have great toe boxes (but the Cursoris is slightly better).
- Longevity. Neither last very long, with the exposed midsole wearing quickly enough to make the overall cost per mile quite high.
Advantage One²
- Cushioning . The One² is more thickly, softly cushioned, though the Cursoris is pretty good.
- Availability. The Cursoris is hard to get hold of and is discontinued.
Advantage Mizuno Cursoris
- Price. The Cursoris is often available at a much lower price (if you can find it).

Altra One2 top	Altra One2 bottom	Altra One2 inside	Altra One2 outside
Mizuno Wave Runner Cursoris top	Mizuno Wave Runner Cursoris bottom	Mizuno Wave Runner Cursoris inside	Mizuno Wave Runner Cursoris outside

4.4 One2 and Altra Torin

Comparing the One² and the Altra Torin:

Similarities
- Drop. Both are zero drop.
- Shape. Both have good toe boxes.
Advantage Altra One²
- Cushioning . The Altra One² is a lot more softly cushioned.
- Weight. The Altra One² is lighter.
- Flexibility. The Altra One² is a lot more flexible.
Advantage Altra Torin
- Trails. The Altra Torin has better protection on rocky trails.
- Longevity. The Altra Torin lasts a lot longer.

Altra One2 top	Altra One2 bottom	Altra One2 inside	Altra One2 outside
Altra Torin top	Altra Torin bottom	Altra Torin inside	Altra Torin outside

5 Gallery

The One² and the Altra Olympus from the outside view.	The One² and the Altra Olympus from the inside view.	The One² and the Altra Olympus from the top view.
The Adidas Energy Boost, Saucony Virrata, One², and the Mizuno Cursoris. (Top to bottom, left to right.)	The One², Adidas Energy Boost, Mizuno Cursoris, and the Saucony Virrata. (Left to right.)	The One²and the Adidas Energy Boost from above.
The One²and the Mizuno Cursoris from above.	The One²and the Altra Torin from above.	The One²and the Saucony Virrata from above.
A close up of the cross-section through the midsole. Each of the blocks should be roughly the same thickness, but you can see where one of the blocks has been worn down quite a bit.	Another view of the wear on the outsole after a little over 200 miles.	Altra The One² cross section

6 A Comparison with other Recommended Shoes

If you're looking for "the best of the best" running shoe, here are my top picks. Of course, the answer will depend a little on what you're looking for, so I have recommendations for various categories.

Best All Round Shoe. The Altra Escalante is my current all-round favorite. It has plenty of cushioning for its weight, it has a very springy midsole, it lasts well, and it has a shape that's closer to the shape of a human foot than most shoes. It's a great shoe for any runner, including those Starting to run. It's also a fairly easy shoe to find due to its popularity.
Best Maximalist Shoe: If you want something massively cushioned, then I'd recommend the Saucony Kinvara 8. It's remarkably light and remarkably cushioned, beating Hoka at their own game.
Best Optimal Shoe: For those looking to trade cushioning for speed, the Nike Zoom Streak LT 3 was my top pick, but the latest version (LT 4) falls short of it's predecessor. There are lots of great optimal running shoes, which provide just enough cushioning with light weight and minimal frills, but all have their weak spots. Probably the best option at the moment is the Altra Vanish-R, which offers great cushioning for just over 5oz/150g.
Fastest Shoe: If you really want speed, then check out the Nike Vaporfly 4%. It's light, massively cushioned, and has a carbon fiber plate. Nothing comes close, not even the now defunct New Balance RC5000‏‎ or New Balance RC5000v2‏‎. There are a number of caveats; it's really expensive, it's really hard to find, and there's a significant injury risk.
Best Minimalist Shoe: Merrell Trail Glove. I recommend the trail glove for road running in spite of the 'trail' moniker. It's not a fast shoe by any means, but it's comfortable and will last well.
All Terrain Shoe. For trail running, I've become a fan of Altra, and I think their best shoe is the the Altra Timp, though the Altra Lone Peak is really close.
Honorable Mention: It's not really a running shoe, but the Vivobarefoot Ra is comfortable, minimalist and can more or less pass as a dress shoe. I've worn mine to weddings with a suit and they've not looked out of place. You can run in the Ra, but the leather means it doesn't breathe well.

For a more detailed on running shoes see the Recommendations for Best Running Shoes. This table lists the key attributes of What to Look for in Running Shoes. For more detailed information, on the shoes see detailed shoe comparison.

Full Review	Brand	Name	Rating	Recommended price	Benefit	Weight (oz)	Penalty (sec/mile)	Forefoot Thickness	Heel Thickness	Loaded Drop mm	Cushioning	Flexibility
Saucony Type A Review	Saucony	A/A7	Recommended	$100	6.4	6.7	12.1	19	22	1	4.3	7
Saucony Type A6 Review	Saucony	A6	Highly Recommended	$100	8.2	6.1	9.5	17	21	4	5.0	7
Saucony Type A8 Review	Saucony	A8	Highly Recommended	$90	7.5	6.2	9.7	19	20	-1	4.7	7
Adidas Adios Boost 2 Review	Adidas	Adios	Worth considering	$140	4.7	8.6	13.4	17	27	11	4.0	6
Hoka Bondi 5 Review	Hoka	Bondi	Recommended	$150	6.1	11.6	18.1	38	42	5	7.1	2
Hoka Clayton 2 Review	Hoka	Clayton2	Highly Recommended	$150	9.1	8.3	12.9	23	28	1	7.5	5
Hoka Clifton 4 Review	Hoka	Clifton4	Worth considering	$130	7.7	9.3	14.5	30	35	10	7.2	3
ON Cloudflash Review	On Cloud	Cloudflash	Worth considering	$180	4.4	8.3	14.6	19	26	7	3.7	6
On Cloudracer Review	On Cloud	Cloudracer	Worth considering	$130	5.7	8.2	12.8	19	27	5	4.7	7
ON Cloud X Review	On Cloud	CloudX	Not recommended	$140	4.5	8.3	16.3	21	27	7	3.8	7
Mizuno Wave Cruise Review	Mizuno	Cruise	Worth considering	$120	6.6	5.9	12.5	17	20	7	3.9	6
Newton Distance IV Review	Newton	Distance	Worth considering	$155	7.5	9.1	14.2	26	31	3	6.8	5
Asics Gel DS Racer 10 Review	Asics	DS Racer	Worth considering	$110	8.2	7.0	10.9	21	26	6	5.8	5
Altra Duo Review	Altra	Duo	Recommended	$130	6.0	8.4	13.1	29	29	1	5.0	5
Mizuno Wave Ekiden 8 Review	Mizuno	Ekiden	Worth considering	$115	5.7	5.7	14.6	13	18	6	3.2	8
Saucony Endorphin 2 Review	Saucony	Endorphin 2	Worth considering	$115	8.0	5.1	9.6	15	13	-1	4.1	8
Adidas Energy Boost Review	Adidas	Energy	Worth considering	$160	7.2	10.0	15.6	20	30	7	7.2	5
Altra Escalante Review	Altra	Escalante	Best of the Best	$130	9.1	8.7	13.5	28	25	-1	7.9	6
Altra Escalante 1.5 Review	Altra	Escalante 1.5	Best of the Best	$130	8.2	9.0	14.0	26	27	-1	7.4	7
Saucony Fastwitch Review	Saucony	Fastwitch	Highly Recommended	$90	9.5	7.1	11.1	20	22	4	6.8	7
Topo Fli-Lyte 2 Review	Topo	Fli-Lyte2	Highly Recommended	$100	6.7	9.1	14.2	24	26	3	6.1	5
Reebok Floatride Run Review	Reebok	Floatride	Worth considering	$150	7.7	9.6	14.9	28	34	10	7.4	5
Saucony Freedom Review	Saucony	Freedom	Recommended	$160	5.4	10.7	16.6	25	29	3	5.8	6
Skechers GORun 4 Review	Skechers	GORun	Not recommended	$100	6.1	7.5	11.7	15	23	3	4.5	7
Skechers GOrun Ultra 2 Review	Skechers	GRU	Worth considering	$90	7.5	10.0	15.6	28	34	8	7.5	4
Asics GT 2000 Review	Asics	GT 2000	Not recommended	$120	4.8	11.2	17.4	28	35	5	5.4	2
New Balance Hanzo S Review	New Balance	Hanzo	Worth considering	$110	7.6	6.9	10.7	21	19	2	5.2	5
Hoka Hupana Review	Hoka	Hupana	Recommended	$115	6.1	8.9	13.9	31	36	7	5.4	4
Asics Gel Hyper Speed 7 Review	Asics	Hyper Speed	Highly Recommended	$75	10.9	6.3	9.8	22	26	5	6.8	6
Altra Instinct 4.0 Review	Altra	Instinct 4.0	Worth considering	$120	6.0	9.8	15.3	29	25	-1	5.9	5
Asics Tarther Kainos 3 Review	Asics	Kainos	Worth considering	$130	10.0	6.9	10.7	17	27	9	6.8	6
Altra King MT 1.5 Review	Altra	King MT	Recommended	$140	7.5	10.7	16.7	19	21	3	8.0	5
Saucony Kinvara 8 Review	Saucony	Kinvara 8	Best of the Best	$110	9.3	8.6	13.4	26	31	3	8.0	5
Altra Lone Peak 3.5 Review	Altra	Lone Peak	Highly Recommended	$120	4.2	11.4	17.7	24	25	4	4.8	5
Nike Zoom Streak LT 3 Review	Nike	LT3	Best of the Best	$80	9.8	5.4	8.4	16	21	5	5.3	7
Nike Zoom Streak LT 4 Review	Nike	LT4	Recommended	$90	8.5	5.5	8.5	15	21	3	4.6	6
Nike LunarSpider R5 Review	Nike	LunarSpider	Recommended	$125	6.9	6.7	10.4	17	21	3	4.6	6
Hoka Mafate Speed Review	Hoka	Mafate	Best of the Best	$170	7.6	11.9	18.5	39	40	4	9.0	1
Pearl Izumi EM Road N0 v2 Review	Pearl	N0	Highly Recommended	$100	7.9	6.5	10.1	14	20	4	5.2	8
Saucony Nomad Review	Saucony	Nomad	Worth considering	$110	4.3	10.5	17.2	25	27	2	4.5	4
Hoka Odyssey Review	Hoka	Odyssey	Highly Recommended	$130	8.5	9.4	14.6	37	45	5	8.0	3
Altra Olympus 2.5 Review	Altra	Olympus	Highly Recommended	$150	4.6	11.8	18.4	35	34	0	5.4	6
Altra One 3.0 Review	Altra	One	Recommended	$100	6.1	8.8	13.7	23	23	0	5.4	6
Altra Paradigm 4.0 Review	Altra	Paradigm	Highly Recommended	$150	5.3	11.0	17.1	28	30	5	5.8	8
Asics Piranha SP 5 Review	Asics	Piranha	Recommended	$100	10.1	4.2	6.5	11	15	3	4.2	9
Brooks PureFlow 5 Review	Brooks	PureFlow	Worth considering	$110	6.0	9.7	15.1	26	29	5	5.8	8
Salming Race Review	Salming	Race	Worth considering	$130	6.9	6.5	10.1	16	19	4	4.5	6
Altra Escalante Racer Review	Altra	Racer	Highly Recommended	$140	6.6	7.6	11.8	24	26	6	5.0	8
New Balance RC1600 v2 Review	New Balance	RC1600	Highly Recommended	$110	8.8	5.6	8.7	15	21	5	4.9	8
New Balance RC5000v2 Review	New Balance	RC5000v2	Best of the Best	$125	14.2	4.0	6.2	13	21	6	5.7	7
Skechers GoRun Ride 3 Review	Skechers	Ride	Worth considering	$85	5.9	8.5	13.2	18	28	6	5.0	8
Nike RN Distance 2 Review	Nike	RNDist2	Worth considering	$120	8.0	9.2	14.3	25	28	4	7.4	7
Inov-8 RoadXTreme 220 Review	Inov-8	RXT-220	Worth considering	$120	5.2	8.0	18.2	14	17	3	4.2	8
Salomon Sense Ride Review	Salomon	Sense	Worth considering	$120	8.5	10.0	15.6	26	29	6	8.5	0
Altra Solstice Review	Altra	Solstice	Highly Recommended	$90	7.1	8.1	12.5	23	25	0	5.7	5
Topo ST-2 Review	Topo	ST-2	Highly Recommended	$90	8.2	7.3	11.4	20	18	0	6.0	7
Hoka Stinson Lite Review	Hoka	Stinson	Highly Recommended	$160	7.3	11.6	18.1	35	40	6	8.5	0
Altra Superior	Altra	Superior	Highly Recommended	$110	5.6	9.9	15.5	21	25	-1	5.5	4
Adidas Takumi Sen 3 Review	Adidas	Takumi Sen 3	Highly Recommended	$160	7.7	6.6	10.2	17	21	4	5.1	5
Topo Terraventure	Topo	Terraventure	Review Pending	$110	2.6	10.8	27.5	24	24	0	2.8	10
Altra Timp Review	Altra	Timp	Best of the Best	$130	3.7	11.6	18.1	30	31	-1	4.3	6
Altra Torin 2.0 Review	Altra	Torin	Worth considering	$125	3.4	9.6	20.7	30	25	1	3.3	9
Altra Torin 3.5 Review	Altra	Torin 3.5	Worth considering	$125	5.8	9.3	14.5	27	28	0	5.4	8
Hoka Tracer Review	Hoka	Tracer	Recommended	$130	7.2	7.4	11.5	21	24	2	5.3	5
Merrell Trail Glove 4 Review	Merrell	Trail Glove 4	Best of the Best	$100	3.4	8.4	23.8	13	13	0	2.8	10
Topo Tribute Review	Topo	Tribute	Recommended	$100	5.9	7.3	11.4	20	18	-1	4.3	6
Mizuno Wave Universe 5 Review	Mizuno	Universe	Highly Recommended	$125	10.7	3.1	10.6	9	12	1	3.3	9
Altra Vanish-R Review	Altra	Vanish-R	Recommended	$100	16.1	5.3	8.2	19	21	4	8.5	6
Merrell Vapor Glove 3 Review	Merrell	Vapor Glove 3	Highly Recommended	$85	2.1	6.1	27.6	6	5	0	1.3	10
Nike Vaporfly 4% Review	Nike	Vaporfly	Best of the Best	$250	10.4	7.2	11.2	25	37	8	7.5	2
New Balance Vazee Pace Review	New Balance	Vazee Pace	Worth considering	$110	6.0	8.6	13.4	18	24	6	5.2	5
Asics TartherZeal 3 Review	Asics	Zeal	Worth considering	$140	10.9	6.3	9.8	17	27	9	6.8	6
Saucony Zealot 3 Review	Saucony	Zealot3	Recommended	$130	8.9	9.5	14.8	29	32	4	8.5	6
Nike Zoom Fly Review	Nike	Zoom Fly	Worth considering	$150	8.3	8.7	13.5	29	36	8	7.2	3

It's not a running shoe, but I love the Hoka Tor Ultra hiking boot and I've tested the Altra Lone Peak Boot, the Hoka Tor Speed 2, and the Inov-8 Roclite 325 hiking boots
Older shoe reviews: Saucony Hattori Review, Mizuno Cursoris Review, Skechers GO Bionic 2 Review, Hoka Clifton Review, Saucony Virrata 2 Review, Brooks PureCadence 3 Review, Brooks PureConnect 3 Review, Brooks PureFlow 3 Review, Skechers GO Bionic 2 Review, New Balance 980 Review, Brooks Transcend 2 Review, Hoka Huaka Review, Patagonia EVERlong Review, Asics 33-DFA Review, Hoka Conquest Review, Saucony Cortana Review, Puma Faas 100 R Review, Saucony Fastwitch Review, Nike Free Review, Asics Gel Lyte 33 Review, Skechers GOmeb Speed Review, Skechers GOrun Ultra Road Review, Nike LunaRacer Review, Altra Paradigm Review.

Altra One2 (One Squared) Review

Contents