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SoleStridePath

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Flex the sole

Where the sole bends, how much force it takes and whether it bends at all. Flexible appears on several listings in this catalog with no figure attached, and your hands resolve it faster than any specification would.

What you need (4)

  • The shoe itself, once it has arrived
  • Both hands
  • A flat surface to set it down on afterwards
  • The listing text open, so you can see which word you are testing

5 steps

  1. Hold the heel in one hand and the toe in the other

    Grip the heel counter firmly and take the front of the shoe in the other hand. You are not trying to break anything. You are trying to find out where the sole has been designed to hinge, which is a fact about the object.

  2. Press the toe up toward the heel and note where it folds

    Watch the crease. A sole that folds across the ball of the foot behaves differently from one that folds halfway along its length, and both differ from one that folds nowhere in particular. Note which of the three you have.

  3. Note roughly how much force it took

    Two fingers, one hand, or both hands with effort. That is a three-point scale, it is entirely subjective, and it is still three points more resolution than the word flexible carries on its own.

  4. Twist the shoe along its length

    Hold heel and toe and turn them in opposite directions. Torsional stiffness is a separate property from bending stiffness and no listing in this catalog mentions it at all. Note whether it turns easily, a little, or not at all.

  5. Compare against the listing word

    Now read what the seller wrote. Flexible, thin sole, ground feel, flex pillars. Then decide, for yourself, whether the word and the object are describing the same thing. That comparison is the whole method of this site, done by hand.

Your hands are not a calibrated rig. They are still better resolution than the word flexible.

What it tells you (4)

  • Where the sole hinges, which is a construction fact and is visible in the crease.
  • Roughly how much force the bend takes, on a crude but repeatable scale.
  • Whether the shoe resists twisting, which no listing in this catalog discusses.
  • Whether a flexibility word in the listing corresponds to anything in the object.

What it does not tell you (4)

  • Nothing about your health, your gait or anything about your body. This is a test of an object.
  • Nothing about how the sole will behave in six months, since foams and rubbers change with use.
  • Nothing about grip, which is a separate property tested a separate way.
  • Nothing comparable between people, since your hands are not a calibrated rig.

Claim words this bears on (4)

  • Barefoot and ground feel — Barefoot, minimalist and ground feel have no published definition and no threshold. No body says how thin a sole must be to earn any of them, and no listing in this catalog gives a stack height.
  • Memory foam and cushioning — Memory foam names a material family and nothing else: no density, no thickness, no rebound figure. Test methods for flexible cellular materials exist, and no listing in this catalog cites one.
  • Grounding and copper — This claim has no defined measurement and no recognized standard. This site can neither confirm it nor refute it, and records it here as a word that appears in a listing.
  • Non-slip and slip resistant — A published test method exists — ASTM F2913, which measures dynamic coefficient of friction on a whole-shoe rig — and nothing obliges any seller to run it. One listing in this catalog names a standards body; twelve use the adjective alone.

Sources (3)