New runners are especially susceptible to shin splints, Achilles tendinitis, plantar fasciitis and knee pain, according to experts we interviewed for this guide. A lot of these come from doing too much too quickly and bad shoes. A good way to avoid injuries is to take things slow, have proper form and incorporate strength training. If you’ve never run before, five to six days of consecutive running will likely cause an injury, said Junko Kazukawa, an ultrarunner and personal trainer at the Colorado Athletic Club.