“Heel-toe drop” is a phrase thrown around a lot by minimalist shoe fans and manufacturers. It is defined as the height differential between the thickness of the sole of a shoe under the heel relative to the toe (typically reported in mm). For example, if the sole of a running shoe is 30 mm thick at the heel, and 20 mm thick at the toe, the shoe has a 10 mm drop. On average, traditional running shoes have heel-toe drops of around 12 mm, with larger amounts of fancy padding to offset the effects of heel-striking usually leading to even higher differentials. Minimalist shoes, on the other hand, have much lower, or, preferably, non-existent heel-toe drops (AKA zero-drop). This makes sense, because if you’re trying to mimic the “barefoot experience”, your foot has no natural heel-toe drop, so neither should your shoes! That being said, heel-toe drops of minimalist shoes typically range from 0 mm (e.g., Vibram FiveFingers, Merrell Barefoot, VIVOBAREFOOT) to 4 mm (e.g., New Balance Minimus, Skechers GORun, Brooks PureProject).
As many of you may know from our Vibram Transition Series, I transitioned into minimalist footwear with the help of my trusty pair of bright pink and orange Vibram FiveFinger Bikilas, a most-decidedly zero-drop shoe. However, when winter finally rolled around, FiveFingers were, unfortunately, not going to cut it when it came to keeping our toes warm and dry in the Wisconsin snow and ice. You can read more about it here, but to make a long story short, I landed on the New Balance Minimus Multi-Sport WO10, a water-resistant minimalist shoe that sports a 4 mm heel-toe drop as my winter running shoe of choice.
For those of you who don’t know me well, I tend to obsess about the details a little more than the average person. Ok, ok, a lot more than the average person. As you might imagine, then, switching from a zero-drop shoe to a 4 mm-drop shoe presented me with a bit of a challenge. I actually had to ask myself, “What is 4 mm, really?” To put it in perspective for you, a dime is about a millimeter thick. Stack four of them together, and you’ll quickly discover that 4 mm does not an impressive tower make. So, considering that I had never once thought about the heel-toe differential of my shoes for the first 23 and a half years of my life, I couldn’t believe that I was agonizing over the effect 4 lousy millimeters might have on the midfoot form I had worked to transition to in the preceding five months.
Lucky for me, and much to my relief, muscle memory is a beautiful thing, and my leg and feet muscles were still able to maintain a midfoot strike despite the 4 mm drop, so not all was lost. However, I swear the presence of the 4 mm drop does make a difference. I’m aware that this sounds like a “Princess and the Pea” situation, but you can definitely feel the 4 mm drop when you stand in the shoe and I seem to lose some of my efficiency when I run in the Minimus vs. a pair of VFFs. Every time I run in my Minimuses (Minimii?), I find that I run about 30 seconds slower per mile than in my VFFs and feel significantly more tired during my run. At first, I thought it was perhaps the extra weight and thickness of the Minimus’ sole that was slowing me down. Recently, though, I’ve tried running in a pair of Merrell Barefoot Pace Gloves, which are of a similar sole-thickness to the Minimus, but are zero-drop and about 1 oz lighter, and voila! My pace immediately got faster and my energy levels went up while I was running. Somehow I doubt that 1 oz of added weight added 30 seconds to my pace per mile, so I am therefore left believing that it must be the 4 mm drop that is affecting me when I run and I can’t quite explain it!
I still find the New Balance Minimus Multi-Sport to be a great cold-weather alternative to the Vibram FiveFingers (at least until the Fall 2012 line featuring water-resistant VFFs is released). It is an attractive-looking and comfortable shoe and at least allows me to maintain the muscles I built up switching to a midfoot foot strike, but I am having trouble getting over the apparent effect it has on my pace and energy levels when I run. And who knows? Maybe it’s all in my head–the brain is a weird thing! Do any of you have experience running in zero-drop versus 4 mm drop shoes? Did you find that it made a difference in your form or efficiency when you were running?[UPDATE 2/3/12, 7:30 AM] Edited post to correct weight difference info about NB Minimus vs. Pace Glove.