Performance Midsoles
Selection, Performance, Care, and What to Look For
Meindl has been building exceptional footwear for over 300 years using only premium materials — Gore-Tex®, Vibram®, premium insulation. These are technologies most buyers research and understand. But one critical layer rarely gets discussed: the midsole. Without educating our customers on the midsole, we’re not giving you the tools to make the best decision on your next purchase.
The midsole is the layer of material between the inner and outer soles. It absorbs shock and adds protection, structure, and support between your feet and the ground.
Two main midsole materials are used in high-performance footwear: EVA (ethylene vinyl acetate) and PU (polyurethane). Each is used for different purposes, and each has advantages and downsides.
EVA (Ethylene Vinyl Acetate)
The most common midsole material in footwear. EVA is a lightweight foam made of thousands of compressed gas-filled bubbles — lightweight, cushioning, and shock-absorbing. It’s also highly compressible and easily manipulated during manufacturing, making it suitable for everything from alpine boots to walkers.
Pros: More lightweight than PU, improved flexibility, excellent shock absorption. Ideal for light hiking and running shoes where weight matters.
Cons: EVA holds a memory — after thousands of steps, the foam’s ability to rebound decreases, making boots feel flat. There won’t be visible defects, but comfort and support diminish over time. This is why many recommend replacing EVA-soled footwear more frequently.
PU (Polyurethane)
A denser synthetic material most commonly found in high-performance trekking boots. The majority of Meindl USA boots use polyurethane for its performance and longevity.
Pros: PU does not hold a memory — midsoles always rebound to the same shape and provide the same cushion from day one through the life of the boot. More lateral support, virtually eliminates stone bruising, and delivers more years and miles of comfortable fit.
Cons: PU can break down over time through a process called hydrolysis — a gradual deterioration caused by moisture, UV rays, and heat. Unlike EVA, when PU breaks down it can be visibly apparent, with midsoles potentially crumbling or detaching. This is a natural process, not a manufacturing defect.
How to Extend the Life of Your Midsoles
The best thing you can do for PU midsoles is wear your boots. Walking works air in and out of the midsole pores, preventing moisture buildup and slowing hydrolysis. When storing:
- Store in a dry, cool, ventilated space — not near heat sources or in humid areas.
- Keep boots clean. Clean regularly after hard use in wet or muddy environments. Learn how to clean and condition your boots.
Signs of Hydrolysis to Watch For
- Fine granular black specks on the floor or shelf where you store your boots — a sign of advanced hydrolysis on the outer edges.
- If boots haven’t been used for years, take a test hike before relying on them in the field.
- Perform a flexibility test: press a blunt object (ballpoint pen with cap on, key) into the midsole heel. PU should give under moderate pressure and rebound. If it has hardened with limited rebound, hydrolysis has progressed.
Once hydrolysis starts there’s nothing to stop it — but the good news is Meindl boots can be resoled, giving well-broken-in boots a new life. Questions? Call us at 1-833-563-0101 or email info@meindlusa.com.
