Pace-Tuning Explained

Pace-tuning is the adjustment of the midsole properties in the forefoot relative to the heel so that the vertical impact and side-to-side jerk may be minimized without increasing the stress between the heel and forefoot. The faster your pace, the more side-to-side jerk with each step. We minimize the side-to-side jerk by making the forefoot more firm. So the faster the pace, the more firm the forefoot needs to be. But here's the problem: as the difference in density between heel and forefoot increases, so does the jerk in the tendons and fascia under your foot. That's right, a third thing to worry about!  When they stretch farther and more rapidly, the stress is increased. Eventually, underfoot stress can lead to injury.

The way pace-tuning works is to increase the densities in the heel and forefoot so that the jerk experienced under the arch area is minimized at the same time as the vertical and side to side jerks are minimized. The result are shoes with different density properties appropriate to different paces. Your weight isn't a factor, because jerk is related to velocity, not to force.

Since pace-tuning maintains the balance between heel and forefoot, you can run safely at any pace in any Vimazi shoe. The reason you want a faster pace shoe for doing a lot of training at a faster pace, is to better protect against the side-to-side jerk. Since we tend to increase our cadence at faster paces, the vertical jerk is actually less at faster paces, so the heel can be firmer and not increase the impact jerk. At the same time, the firmer heel keeps the difference between heel and forefoot from causing more stress under the foot.