Altra Running Instinct 4.5 Review: A Heavier Trainer with Sublime Upper Comfort and Room, over a Lively, Firm Base

Article by Sam Winebaum, Dom Layfield and Dave Ames

Altra Instinct 4.5

Introduction
Sam: The Instinct is Altra's original road shoe. With version 4.5 the big news is that it gets a soft engineered mesh upper for the first time. Combining Altra's FootShape toe box with this type of upper for me really delivers a front of the shoe comfort that is second to none, yet securely held. I do not have any toe or front of the foot problems but those that do should really try this shoe. The ride is on the firm side yet well cushioned and because of the Inner Flex grooves surprisingly flexible given the high forefoot stack.


This is not a light shoe at 10.6 oz in my size 8.5. Much of the unusual weight seems to come from a 1.3 oz "yoga mat" like insole, double or more the weight of conventional insoles. Out on the road it ran somewhat lighter than its weight and due to its superior flexibility was more lively than similar shoes with "premium" comfort uppers and similar heft. And all the comfort at $30-$40 less than many competitors. The Zero Drop, all Altra have a heel at the same height as the forefoot, was barely noticeable if at all. While I have run in many Altra this was my first Instinct and I was very pleasantly surprised.

Stats
Weight: My sample US Men's 8.5 weighs 10.6 oz/300 g. A standard size 9 should weigh about 10.8 oz
Stack Height: 25mm heel/25mm forefoot, Zero Drop
Price: $110. Available now including from Altra here

First Impressions and Fit
Sam: I was sent true to size and that was correct for me. Wow what step in comfort! My narrow to medium feet were delighted by the incredible soft roomy toe box and secure mid foot hold. I found the heel hold somewhat loose but after doing a lace lock was fine. Nobody should need to size up in this shoe.

Dom:  My first thoughts were “plush” and “roomy”.  Most Altras have a spacious toebox, and these fully live up to that reputation, with both width and height.   Like Sam, I found the heel loose.  It felt like a shoe for someone with much stouter ankles than my bird-like legs.  Given that the rest of the shoe felt oversized, the mid-foot retention was surprisingly good.

Dave:  2018 is the first year, I’ve really taken a good dive into product from Altra Running.  FYI, I’m still getting used to the toe box and zero drop (used to run a ton in Newton MV-3, NB Minimus) but I get what they are throwing out there.  Anywho, what a nice shoe!  They really ditched the “weird” running shoe look here and finally developed something that looks like a daily trainer.  I’m probably most impressed by this.  I have a very narrow foot, but found no problems with sizing or width here on the Instinct 4.5 and really enjoyed the wiggle room in the toe box.  I did have to use the last eyelet, which is a pet peeve of mine in run shoes, to get a snug and secure fit.

Upper

Sam: The star of this update is the engineered mesh upper and how it delivers on the promise of FootShape comfort up front.

There are no overlays or stiffeners in the toe box what so ever up beyond a few very thin printed overlays on the lateral side.  Gone is the substantial stitched on front bumper of the 4.0. The entire front of the shoe is soft and foot shaping although to keep it all secure the engineered mesh has minimal stretch.

Engineered mesh uppers, all the rage these days, and I prefer them to knit, with their minimal overlays can present mid foot hold challenges. Most often shoe manufacturers solve this problem with an inner bootie or sleeve. The Instinct 4.5 has such an inner sleeve and given the overall volume and softness of the upper it wisely does not try to make it overly stretchy or minimal yet at the same time it is not overly snug leading to the arch area bite such sleeves can cause.

The tongue is moderately padded and soft. The ankle collar and achilles collar amply padded and also soft.  The heel counter plastic is moderately stiff but not brick hard. 

While I found achilles hold fine and had no heel slip,the combination of the very wide foot opening and soft padding had me needing to do a lace lock for a bit rear of foot  security. 

Fortunately, and breaking with a recent and for my feet an unwelcome trend at Altra, the height of the ankle collar is raised. Many recent Altra, including the new Duo (RTR review) and even Altra trail shoes have had for my taste a very low ankle collar that just doesn't secure the foot as well as I would like.  Others with different ankle bones may disagree. Here we have a decent height collar which probably saves the day given the very wide foot opening.

The sock liner insole is made of a thick spongy yoga mat type material. While it contributes to step in comfort and may be adds some softness to the ride, it weighs 1.3 oz, so double or more] than a conventional sock liner. It can always be swapped for something else lighter and thinner, which in my case might have had me sizing down a half, or for an aftermarket orthotic type as there is plenty of room for such more substantial insoles in the Altra. One imagines all kinds of orthotics would work well in the Instinct.

Dom:  A fine-looking shoe, the Instinct 4.5 is strikingly plush and well-padded, particularly around the heel collar.  I found the heel collar to be oversized, but I have narrow ankles.  While the Instincts have an extra eyelet to permit heel-lock lacing, it was sub-optimally positioned to maximize heel retention.

LEFT: Instinct 4.5    RIGHT: Torin 3.0

Dave:  The upper is real nice.  The engineered mesh is smooth, but doesn’t lack the aggressiveness to mold your foot.  I always worried about that due to the oddly shaped toebox (which I am digging more than ever, btw)  My heel was locked down nicely and honestly when this shoe is on my feel I rarely notice it is a zero drop shoe.  It feels like a normal trainer in terms of fit for me.

Midsole

Sam: The midsole combines Altra's resilient somewhat bouncy A-Bound layer under foot with Altra's EVA.

A key component, unseen, is Altra's InnerFlex, a tennis strings like grid in the midsole to enhance flexibility. Inner Flex is fantastic for increasing the flexibility of high forefoot stack shoes and was marvelous in the Duo with its yet higher 31mm stack. Here in combination with the  effective layout of the outsole it gives the Instinct a relatively long quite easy flex which I found made slower pace transitions easy and climbing excellent. The flexibility may also enhance outsole wear.

Dave:  Killer midsole here!  The A-Bound creates a great amount of pop for me upon toe off, yet the general EVA gives a really smooth transition from heel to toe.  My runs feel uber smooth in this shoe and I found no difficulty in trying to “figure out” the zero drop, like many can struggle with in Altra in my opinion (just the early stages of runs) - - I find this midsole to pack so much power that it is easy to crank up the pace and run tempo the Instinct 4.5. I was awarded with a  \nice smooth landing each and every stride.  Something very important to me in testing shoes.  No one wants to continually “wait” for a shoe to come alive.

Outsole

Sam: The outsole for all intents and purposes full coverage, and relatively firm. I noticed some scuffing of the fine outer patterns at the very front of the toe and my usual heel wear area at 12 miles.

Dave:  Really nice outsole and handled the roads well.  The outsole is very dialed in and had no issues on wet surfaces or cinder gravel or trail.  In fact, and I know Dom may disagree here, but I see this shoe performing awesome on some nice single track rollers in the Santa Monica mountains for me.  Kinda like a shoe that will do everything road vs. light packed trail, when maybe you don’t want to reach for the Superior 3.5 (Gave the Superior 10/10 btw! RTR review)

Ride

Sam: My testing was shall we say decisive. I took them out of the box and ran a hilly 11.5 miler at a variety of paces on Park City roads. As with all transitions to zero drop one should gradually work into the lower stacks, most shoes today range from 4mm to 10mm. I usually run in shoes from 4mm to 10mm and alternate stack heights almost daily.  I prefer a moderately firm ride as here over very soft ones. I had zero, pun intended, with the zero drop and hadn't run in an Altra in over a month,

The ride is on the firm side and I worried that my legs would end up trashed given the hills and distance. Not at all the case.  I added miles to my run as I went along exploring the steep side streets in Park City.

While not a fast shoe, likely mostly given the weight, I walked away from the run with very fresh legs. In the final miles I did have a touch of forefoot pain but nothing unusual for the distance. As with all Altra with InnerFlex and that wide on the ground front platform, they climb exceptionally well. The steep downhills were stable and comfortable but not at the level of the similarly firm Salomon Sonic RA and Max, with their vibration attenuation.  I did struggle a bit to pick up the pace on the flats but after all the Instinct is designed to be a durable, comfortable daily trainer.

Dom: At the time of writing, I’ve only managed two runs in the Instinct.  The first was on-road, and was pleasant enough: the Instinct 4.5 were an agreeable but unremarkable companion.  The shoes were comfortable, but a little clunky.  Like most Altras, they steer the runner toward a mid-foot strike (heel landing with more rapid transition to forefoot).  I could cruise for hours, but wouldn’t want to go fast or maneuver rapidly.  Off-road, on technical terrain, they felt downright terrifying: the roomy fit and extra padding that made them super comfy on the flat made them feel insecure and unstable.  They would be fine for smooth mellow trails, but are definitely not recommended for off-camber, steep, loose, or muddy conditions.

Dave:  Smooth yet stable. Powerful yet giving some nice flex via the InnerFlex. I got a nice 8 mile progression in, continually dialing down the pace 10 sec per mile faster.  In the final few miles, for my washed up ass, I was clicking some nice 5:45’s, but my stride was not out of control (currently in the base phase with no real speed coming for a while) - - This is key for me when I want to hammer.  I know immediately if a shoe is going to work at higher end speeds if my form stays consistent.  If it gets sloppy (training in the right ranges, btw) then the shoe probably isn’t going to work for faster sessions.  Hit a recovery day as well and had no issues with the zero drop not being enough for me, which shocked me.  I will probably be a bit careful with this shoe in terms of not “overdoing” the zero drop.  Overall, a very pleasant shoe.

Recommendations and Conclusions

Sam: While I am certainly not a podiatry specialist, The Instinct clearly is a great shoe for runners with problem toes and wide feet given its supremely accommodating toe box. Its volume should allow easy use of orthotics and after market substantial insoles. I am not a fan of the added weight of the yoga mat insole. Altra could have done better there while achieving the same step in comfort and cushion result. If you like a relatively firm, flexible, stable ride and upper comfort the Instinct is a great choice.

Dom:  The Instinct 4.5 reminded me of old-school Cadillacs.  I’m talking about the indulgently-sized luxury cruisers.  The shoe is roomy, very well-padded, but with a slightly firmer ride than, for example, the Altra Torin.  While some road shoes work decently off-road, these are strictly road-only: the combination of a generously sized toe box, loose heel and no tread made them feel terrifyingly unstable on off-camber, steep, and/or sandy, slippery terrain. 

I really like the Altra Torin, which is lighter than the Instinct, more versatile, provides more cushioning for less weight, and is a better fit (for my feet, at least).  Given the presence of the excellent Torin in Altra’s line-up, I find myself scratching my head somewhat at who the Instinct is targeted at.  I suspect a heavier runner or someone who has problem feet.  Sam may have hit the nail on the head when he remarked that this shoe will allow easy use of orthotics.

Dave:  Perfect shoe for those wanting to brush up on form, yet plenty of shoe for the runner wanting a good daily trainer that seems it will hold up well.  Wouldn’t race or touch the track in it, but a good tempo day, Fartlek sesh shoe and just plain solid for cruiser aerobic miles.  Recovery days, as mentioend earlier, I likely will be grabbing something non zero drop.  Note:  I felt no negative effects of running in zero drop and I these days I am mostly in 8mm-10mm drop shoes.  So don’t fear the drop!  Altra made this friendly enough for any runner.

Sam's Score 9.35/ 10

-0.45 for weight and especially for heavy sock liner insole, double or more the weight of most. 

-0.20 for wide ankle collar and its softness. Other feet may be happy with this design. Rarely do I have to lace lock at true to size but here I did. 

Dom's Score 7/10   
This is not a bad shoe at all, just not suited to me.   It felt heavy, over-padded, and over-sized.   For easy cruising, I could live with the capacious toe box, but my feet were swimming in the extra-large and deep heel.   On the plus side, it’s a very nice looking and comfortable shoe.

Dave’s Score 9/10
-.5 for weight
-.5 for extremely thin laces and couldn’t exactly get the perfect lace up.  Had to lace lock, which I hate doing.

Comparisons

Altra Instinct 4.5 vs. Altra Torin 3 (RTR review)
Dom: The Torin 3.0 stack is higher (28 mm vs 25 mm) but softer, so in practice your foot ends up about the same distance off the ground.  The Instinct has a firmer ride.  To my taste, there’s no question which is the better shoe.  The Torin is lighter by almost 2 oz/55 g, more flexible, better cushioned, and a better fit for my feet.  Instinct felt oversized and cumbersome.

Sam: Torin 3, and before that 2.5, were some of my favorite shoes of the last few years. I prefer the upper comfort and especially the toe overhead room and soft toe box of the Instinct and its firmer ride but as Dom says the Torin crosses over super easily to many trails while the Instinct doesn't. The super wide ankle collar not helping matters on trail. If it wasn't for the weight of the Instinct I would lean towards it for its firmer ride and superior road use upper comfort despite its more limited versatility. Still I give the nod to the Torin.

Reviewers
Dom Layfield is an accomplished trail runner with a background and PhD in bio mechanical engineering from MIT.  His 2017 achievements include first place in the dead of winter 108-mile Spine Challenger race in the UK, breaking the course record by an hour, first place in the Quicksilver 100K in California, and 14th at the Western States Endurance Run.

Sam Winebaum is the Editor and Founder of RoadTrailRun. He has been running and shoe geeking for 45 years. As he turned 60 in 2017 he was thrilled to clock a 1:35.24 half.

Dave Ames is the Founder and Head Coach of Ame For It Run Coaching, a nationwide run coaching business, training athletes of all ability levels from 5K to Marathon.

For Dom, Sam and Dave's full run bios see our Reviewers Bio Page here.

The Instinct was provided at no cost.The opinions herein are entirely the authors'.

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