Purpose: Minimalist running shoes are becoming a more popular choice for runners in the past few years. However, there is little conclusive evidence about the advantages or disadvantages of running in these shoes. Although performance benefits may exist, injury may also occur from the added stress of running without the benefit of cushioning under the foot. Bone marrow edema can be a manifestation of added stress on the foot. This study measured bone marrow edema in runners' feet before and after a 10-wk period of transitioning from traditional to minimalist running shoes.
Methods: Thirty-six experienced recreational runners underwent magnetic resonance imaging (MRI) before and after a 10-wk period. Seventeen subjects were in the control group (ran in their traditional shoes only for 10 wk), whereas the other 19 were in the experimental group (gradually transitioned to Vibram FiveFinger running shoes for 10 wk). The severity of the bone marrow edema was scored on a range of 0-4 (0 = no bone marrow edema, 4 = edema in more than 50% of the length of the bone). A score of 4 represented a stress fracture.
Results: Pretraining MRI scores were not statistically different between the groups. The posttraining MRI scores showed that more subjects in the Vibram group (10 of 19) showed increases in bone marrow edema in at least one bone after 10 wk of running than that in the control group (P = 0.009).
Conclusion: Runners interested in transitioning to minimalist running shoes, such as Vibram FiveFingers, should transition very slowly and gradually to avoid potential stress injury in the foot.