Here’s a tip if you are running in sandals (or without socks) and you are getting a water blister on the bottom of one or both of the balls of your feet:

Here’s the problem – Your feet naturally ‘cup’ on the upstroke as they leave the earth; forming a small vacant hollow in the center of the ball of your foot. Over time this creates a hot spot where moisture and small amounts of dirt collect. This in turn creates a shear stress point where that part of the foot isn’t sliding as you are moving forward which results in a blister.

Solution – Lightly talc the footbed and feet before a run. If you are doing long runs – marathon plus distance  – stop every hour or so and wipe the center of the ball of your foot with your finger and lightly re-talc.