Stress fractures are common running injuries associated with the mechanical fatigue of bone. The metatarsal bones in the foot frequently develop stress fractures due to the repetitive loading they experience while running. Similar to basic engineering materials, the number of loading cycles to bone failure (i.e., stress fracture) increases exponentially with the applied magnitude of loading. Therefore, the objective of this thesis was to examine the relative effects of two potential stressreducing mechanisms – shoe type and stride length adjustment – on metatarsal strains and the probability of failure in running. Running in a minimalist shoe increased metatarsal strains and the probability of failure, while running with a 10% stride length reduction was not effective at reducing metatarsal strains or the probability of failure. These findings offer an explanation for why metatarsal stress fractures are frequently observed in minimalist shoe users, and suggest that running in traditional footwear lowers metatarsal strains.