Midfoot Strikers Are Different from Forefoot Strikers, but Similar to Rearfoot Strikers

Abstract

Category: Sports Introduction/Purpose: Rearfoot strike (RFS) patterns have an impact transient that is associated with running injuries. These transients are not present in FFS patterns. Midfoot strike (MFS) runners are often grouped with FFS runners in studies as they are both non-heel strike patterns and assumed to be similar. However, this has not been tested. Tibial shock (TS) provides a measure of impacts and can be easily assessed in the field. Therefore, the purpose of this study was to compare TS among differing footstrike patterns measured during a marathon race. We hypothesized that MFS would have greater impacts than FFS, but lower than RFS. We also aimed to examine how impacts vary across speeds. We hypothesized that impacts would increase with speed similarly in RFS, MFS and FFS. Methods: 224 healthy runners (119 M, 105 F; 44.1±10.8 yrs) running the 2016 Boston marathon volunteered for the study. Prior to the race, participants ran on a treadmill to determine their habitual footstrike pattern (169 RFS, 32 MFS, 23 FFS). On race day, they ran the course wearing an accelerometer strapped onto their right medial ankle. For this part of the study, the average of the peak TS recorded between the 5 km and 10 km point of the race. This region was used as it had a flat gradient. The peak TS was recorded for each footstrike and averaged over the 5 km distance. This value was compared between the three footstrike patterns using an ANOVA (p<0.05). A regression analysis was used to determine the interaction of FSP and speed for each FSP using individual marathon runner data points. An ANOVA (p<0.05) was used to assess significance of the regression. Results: TS in FFS runners was significantly less than in MFS (P=0.01) and RFS (P=0.01) runners. (Figure 1, top panel). There was no difference between RFS and MFS (P=0.49). When examining the relationship between TS and speed, a significant positive correlation was noted for RFS (p<0.00). and MFS (p=0.02), but not for FFS (p=0.82) (Figure 1, bottom panel). Conclusion: In contrast to common belief, MFS runners exhibit impacts that are like RFS runners, and both are higher than FFS runners. This suggests that MFS runners should be grouped with RFS runners, and not FFS runners, when assessing impacts. In addition, both RFS and MFS runners exhibited greater impacts as speed increased. However, FFS runners appear to be able to maintain lower impacts at faster speeds. This may be due to greater calf activation, mitigating the effect of increasing speed on impacts. This may offer protection from impact-related injuries in FFS runners.