The dirty truth about..

A little while ago a new word was introduced into the running footwear vernacular. It is a word that has confused me and caused me consternation for at least 5 years. Not because I do not understand it, but because I do not understand why we talk about it!

Just why and when we stopped using far more accurate terms like "pitch" or "gradient" is unknown to me, I do however find the term "drop" really annoying!

To the extent that I recently witnessed an elderly woman, who clearly was not a runner or active sports person of any type, ask the shop professional in a technical retail store what "the drop" was on a shoe she was holding. I mean.. holy moly.. what is THAT all about? She might as well have asked him if the shoe was properly grounded for electron transfer as well.

Now let's be clear here, drop and stack are terms that are often confused or used synonymously. They are however quite different. The following graphic explains the difference.

The stack height or simply "stack" describes the thickness of material under either the ball of the foot or the heel. It includes (or SHOULD include), the outsole rubber thickness, the midsole thickness, AND the sockliner thickness.

A very typical expression of stack would be:

rearfoot: 4 mm rubber + 22 mm EVA midsole + 4 mm sockliner = 30mm (4+22+4)

forefoot: 4 mm rubber + 12 mm EVA midsole + 4 mm sockliner = 20 mm (4+12+4)

Clear as mud?

Now.. the 'drop', is the differential between rearfoot and forefoot stacks, so in this example it is:

30 mm (rearfoot) minus 20 mm (forefoot) = drop of 10mm

OK, so that is great and we are all clear.

The reason the discussion has been so vibrant regarding drop is because there is a suggestion that one "drop" is better than another.. for everyone. This is nothing new at all, most companies used a standard drop of 10 mm for eons. Then along came the apocalyptic minimalist movement and told us zero (i.e. 0 mm) was best.. for everyone. 

Craig Payne wrote an interesting piece a while back asking "what is the idea drop? It may be read here.

He made an astute observation:

So basically, at this stage, nothing really underpins the concept of zero drop except a logical fallacy and nothing underpins the 10mm drop other than most runners are using it and we been doing it for a long time, which is also the logical fallacy of ‘appeal to popularity’ which also does not mean its right. It may or may not be right, but popular things have turned out in the past to be wrong, so no one can use that argument either.

I could not agree more, but wait.. there's more, just like the free set of steak knives.

Did you know that there is a material error in all midsole materials? And did you know that error is usually between 5 and 10%?

This means that in a brand new pair of shoes, fresh out of the box, the left shoe quite reasonably may have 2 mm less drop than the right shoe?

And furthermore, did you know that there is a "static drop" and a "dynamic drop"?

Nope, did not think so, and cheers to my mate and super Salomon Senior Product Line Manager Jon Teipen for turning me onto this!

So, consider this.. say these two men are wearing the exact same shoe, same brand, same size, same model

 

Do we agree that it is very unlikely during weight bearing that both pairs of shoes will be loaded the same and therefore have the same drop? 

Because the centre of mass is likely to pass more toward the heel than the forefoot, it is highly likely that man A, the shall we say "prosperous" individual in the middle, will compress the heel of his shoes substantially more than man B on the right, who looks like he could use a good feed.

This is 'dynamic drop', but I have never heard it discussed, and must surely be relevant.

Jon brought this up with me because he was trialing a new shoe with a very soft midsole in the rearfoot, and he felt this change in dynamic drop was injuring his Achilles tendon.

This makes perfect sense to me, even though Jon is only about 60 kg wringing wet!

So, the moral to the story once more is;

• that there is NO perfect drop.
• There is no consistent drop both within and between brands
• The material error means the same brand and model may have a completely different drop
• And.. dynamic drop is real and underlines what we have always known....

Shoe selection is based on individual athlete needs, not what some blogger says is right!