Why I'm Transitioning Back to Altras

History

Since I started running back in 2019 I'd always ran in what I'd call more "natural" style shoes, that is to say they have:

• A zero drop platform, which is a way of saying that the heel and the forefoot are the same height off the ground. Most running shoes have a higher heel than forefoot, from a 4mm to 12mm offset
• A moderate stack height: the distance your foot is from the ground when in the shoes, taking into account the outsole, midsole and insole. I tended to go for shoes around the 20-30mm stack height range
• A good deal of ground feel; the ability to feel rocks, roots and obstacles under your foot through the outsole and midsole.

Here's a diagram that hopefully helps explain this better:

I started with Merrell Trail Gloves (super minimal barefoot style shoes), moved on to Inov-8 Terraultra G 260s for my first marathon, then onto Altra Lone Peaks. The Lone Peaks were the ones, and from this point the shoe I wore on my first 20 odd ultras. I have an especially fond memory of running my first 100k in them, without a single blister, foot or leg issue, then doing a 10k social the next day, tired but happily plodding.

2 years ago almost to the day I got myself a pair of Merrell Agility Peak 5s, a shoe that is the opposite of the above. Having been disappointed with the grip of the Lone Peaks and wanting a bit more oomph, I moved away from the zero drop natural style to a more traditional high stack shoe with 33mm in the forefoot, 39 in the heel for 6mm drop.

The Agility Peaks took me on my first 100 miler, they've gotten me PBs across 2 courses including my nemesis EDDUM race, and have held up nicely throughout with a good shelf life.

Now, with my 2025 season coming to a close as the Pegasus Slam is almost over, why am I starting to shy away from them back towards my first love, the Altras?

I'm seeking to answer 2 questions in this article, both very subjective and based on my own experiences:

• Question 1: is a high stack high drop shoe biomechanically good for you?
• Question 2: does a high stack high drop shoe improve your performance?

Biomechanics

To return to the primary differences between these high stack, high drop shoes and lower stack zero drop shoes, like anything there are advantages and disadvantages to each.

The high stack of the Agility Peaks mirrors the majority of long distance focused shoes you find on the market nowadays: upwards of 35mm cushion at the heel with the intention being protection of your joints as you land whilst helping with propulsion.

Running in them, I've found they work nicely on hard surfaces, cushioning your landing and reducing underfoot fatigue, whilst also acting like a spring with the midsole pushing your forward.

However, high stack heights can have some serious disadvantages:

1. Stability: the higher the stack the less stable you will feel over technical ground: you'll be more likely to go over on your ankle, and will find yourself less able to nimbly position your foot. There's a reason more technical racing focused shoes like the Merrell Long Sky 2 have a much lower heel
2. Impact Force: I've found that in the Agility Peaks I land much, much heavier than I would in thinner shoes. My running seems to compensate for the cushioning, which strangely negates the protection and instead drives the impact forces up my upper leg
3. Ground Feel: All that cushioning means you can't feel the ground under your foot. From a fatigue reduction point of view this is great, but there is a concept called proprioception, the ability for you to control your balance and movement through sensors in your muscles feeding back to your brain. These are muted underfoot in high stack shoes, further leading to more potential instability

In low stack shoes you have to be conscious to land softer to reduce that fatigue, something your body does over time as you adapt to the shoes. However you gain that stability and proprioception back whilst learning to land in a natural way that reduces muscle strain.

The heel to toe drop of a shoe is a tricky one, and like the majority of the content in this article super subjective.

I've found in high drop shoes I tend to get a better feeling of propulsion as the shoe angles my foot forward, giving me a bit of oomph. I prefer how shoes with a drop feel.

However they also encourage more of a heel strike, whilst zero drop shoes tend to encourage more of a midfoot/forefoot strike. The heel strike can, in a similar way to a high stack shoe, cause more impact forces to travel up the leg towards the knee.

Midfoot striking on the other hand tends to utilise your foot's natural spring better, keeping those forces at your lower leg, ankles, feet (which could be argued is what your lower legs are designed for).

High drop shoes can also contribute to instability, the angle your foot lands making it harder to land confidently. Though I will say I've found a drop does tend to lead to faster descending as it encourages you forward due to the angle of the foot, whilst also having more cushioning to mitigate the impact of descending hard, though also encouraging you to land harder than you should.

And a final aside: I've found a high drop tends to lead to more toe bashing as your toes are more likely to slide forward in the shoe to the wall even on a flat surface.

Here's a table from Google Gemini Research outlining the key differences:

So in summary: high drop and stack gives a feeling of increased performance and cushioning, at the expense of stability, with biomechanical issues around impact forces and upper leg pressure.

But do they actually improve performance?

Performance

The most subjective one of all 😂. See before trying the Merrells I was aware of all of the above. I was, and still am, a big advocate of more natural style footwear. So here's the reason I've stuck with the Merrell Agility Peak 5s: they felt FAST. Right from the first run they were light, bouncy, propulsive, whilst begin very technically able with big grippy lugs.

Still to this day I'm yet to find a trail shoe I've felt as driven forward by. It felt like enabling cheat mode on every run.

But were they actually more performant, or was it more how they felt?

I can only speak for my experiences, but here's some examples. For completeness the two shoes stats compare like so:

• Lone Peak: 309g, 0mm drop, 25mm heel, 25mm forefoot
• Agility Peak: 289g, 6mm drop, 39mm heel, 33mm forefoot

The performance comparisons:

• EDDUM
  • 2022 in Lone Peaks: 12:54
  • 2025 in Agility Peaks: 11:52
  • 1 hour 2 minutes is pretty conclusive, though I put that down to being much better at pacing, fuelling and hydrating than the shoes
• VOGUM
  • 2022 in Lone Peaks: 07:46
  • 2025 in Agility Peaks: 07:34
  • 12 minute improvement with 3 years extra training, not a big difference...
• Dennison Round
  • Record Attempt in Agility Peaks: 01:57
  • Relaxed Recce in Lone Peaks: 02:02
  • 5 minutes between a hard push and a chilled run...
• Piglet
  • Pushing Run in Agility Peaks: 04:46
  • Relaxed Recce in Lone Peaks: 04:50
  • 4 minutes between a hard push and a chilled run...

So I'm starting to build up this picture that, despite how the high stack shoes feel the gains are marginal at best, at least in the distances I target. It's especially interesting in regards to the Dennison round and Piglet as I'd not been using zero drop shoes much for over a year at that point so had lost some adaptation.

My Turning Point

I started to dabble in zero/low drop and low stack height shoes again, notably the Altra Mont Blanc Carbons and the Merrell Long Sky 2s, along with hiking in the Altra Lone Peak 9+, and what I found what that my legs had weakened quite substantially.

Specifically, after 2 years of predominantly using the Agility Peaks, I found:

• My soles were under-adapted to thinner cushioning, oversensitive to the ground now and fatiguing quickly
• My calves and ankles struggled to re-adapt to the more natural form
• My knees and upper legs really ached when I lowered the cushion
• I felt especially slow and ploddy

I felt like I'd painted myself into a corner: by focusing on such a protective, cushioned shoe, I'd detrained and weakened my lower leg muscles, taking away that natural resilience I'd had before where I could run for what felt like endless miles in more minimal shoes.

And, comparing my performances, I wasn't convinced it was worth the trade.

Ultimately, I want to aim for longevity here: able to sustain running far into the future and improve my game. I feel like in order to do that I need to be focusing on shoes that facilitate that by strengthening me, rather than over protecting me.

New Rotation

Firstly; the good news is that Altra's zero drop range is on fire this year, with them filling out their catalogue with what feels like an ideal rotation of shoes that is much more competitive than their previous years.

What I like about this especially is that each shoe here compliments the other. As they are all zero drop with a similar stack height (25-30mm), from a biomechanical perspective training in one will improve the same muscles used by another.

First up we have the old classic, the Lone Peak 9+: for me these are daily walking/hiking/office shoes and occasional plodding shoes. This version is especially durable, but also especially heavy, so they aren't my main trail running shoe.

Then we've got the Mont Blanc Speed; basically the shoe I wish the Lone Peaks were. There have a little more cushioning at 29mm stack height, great grip, yet are significantly lighter whilst still having a roomy toe box. These are my main trail running shoes for training.

The Mont Blanc Carbon is next: their carbon plated super shoe for racing. Basically the same as the Mont Blanc Speed but with that plate that acts like a spring.

I'm saving this one for race day due to the cost, however if I'm honest the plate is especially firm and I'm not convinced I like them more than the Speeds yet. They sure do feel fast underfoot, but we've seen where that leads 😅.

Finally the Torin 7/8 as a road shoe. I don't do loads of road running so these daily training / marathon shoes are ideal for speed work and recovery. All my road PBs were done in Torins.

The Transition

If I'm honest it's been harder than expected. I thought that the years I'd spent running in only Altra's would have made it a quick transition, however my body is so used to lots of cushioning and a deeper angle when running now that it's taking a fair bit of adaptation.

I'm starting to feel the benefits again especially in terms of comfort, stability and performance over the trails, but am still feeling more fatigued over distance then I'd like.

The aim now is to continuing training in Altras during the off season with a view to using them next year for the *Ona Series.