I bought these to replace my Saucony Shadow 6000's, a sturdy design that's being discontinued after 20 years. Since I switched to the Guide 6's I'm running farther and my feet and back feel better. Apparently modern design and materials do help. They're also much lighter. I'm no great runner (thirty-forty miles per week at peak season) but I have professional marathoner friends who swear by Saucony's Guide line.