This is good data! I am going to do this. My feet get boogered up pretty good since I quit wearing a green suit. Thanks for sharing.When we ran students thru the special forces training, we used to emphasize conditioning of feet . We used to use tincture benzoin and foot powder to toughen the foot soles. The article is correct core and upper body strength strength is key. Our standards were 12 minute miles for 8 miles and 15 minute miles over that with 45 lbs. That was on sandy trails. There is a different stride people need to learn and focus on stride length when rucking. Your feet will kill you quicker than being out of shape. If you want to last long term, toughen the soles of the feet up. That foot powder and tincture of benzoin will make them like leather. Use the tincture first and then add the powder and let dry. Will not look pretty with sandals, but then who cares.