The Science of Running: Factors Contributing to Injury Rates in Shod and Unshod Populations

Ryan MacKenzie
Lene MacKenzie
Alicia Martinez
Marisol Cardoza


There has been a recent increase in the popularity of minimalist running shoes, which allegedly resemble barefoot or “unshod” running (e.g. Nike Free or Vibram). It is hypothesized that barefoot training improves strength differently than running in shoes or “shod” by activating both extrinsic and intrinsic muscles of the foot.

It has been suggested that footwear influences foot strike pattern (how the foot initially contacts the ground). Foot strike can be described as rearfoot (RFS), midfoot (MFS), or forefoot (FFS). Minimalist footwear is associated with a more anterior strike pattern than traditional footwear (Goss et al. 2012). With shod running (versus unshod), there is a faster loading rate at initial contact (Squadrone 2009), leading some to conclude that shod running correlates to higher injury rates.

There is limited evidence to assess relationships between foot strike patterns and footwear on injury rates. There are biomechanical differences in loading rates, joint position angles, and EMG activity with different foot strike patterns but not with shod or barefoot running. These data suggest that foot strike patterns play a greater role than the shod condition in running injuries (Shih et al. 2013). This study focuses on how injury rates relate to foot strike patterns in habitually shod and unshod runners.