Individuals who are overweight, habitually wear high-heeled shoes, or have suboptimal tibia-to-femur length ratios may be at higher risk for injury or not suited for running.

“if you took the average teenager who for all intents and purposes still has their body intact but either they're too overweight or they've spent too much time in a high shoe meaning a heel to toe ratio that's too great or there's something about the length of their tibia to their femur that just doesn't seem optimal”