Surprise risk: No doubt you've heard devotees swear that running barefoot, or in minimalist shoes, cured their chronic aches. What many would-be converts don't realize is that running unshod requires them to completely change their gait. ACE has found that those who fail to adapt their stride can end up putting even more weight and pressure on the back of their feet than they would while wearing sneakers, which can lead to fractures of the heel—the most serious kind.
Ouch! Factor: 5 if you continue to heel-toe it on concrete or asphalt. (We're referring to physical pain, not the aesthetic pain some people feel while looking at minimalist shoes.)
Sprint safely: Whether you want to run barefoot on the beach or wear minimalist shoes on the sidewalk, start off walking or jogging slowly, and focus on landing on the middle of your foot, not your heel, Matthews says.
Read more: The pros and cons of barefoot-style shoes