Increased Foot and Tibial Angles at Footstrike Decrease Vertical Loadrate in Runners

Category: Sports Introduction/Purpose: It is well established that elevated vertical loadrates on footstrike are a risk factor for developing running injuries. Overstriding, or increased foot and tibial angles at footstrike, has been theorized to increase loading rate. Thus, it is often suggested that runners shorten their stride to reduce their injury risk. However, the relationship between landing alignment and loadrates has not been well established in current literature. Thus, we aimed to investigate the relationship between sagittal plane foot angle (FA) and tibial angle (TA) with vertical loadrates in both healthy and injured forefoot (FFS) and rearfoot strike (RFS) runners. It was hypothesized that as FA and TA increased, loadrate would increase for all runners. Methods: This is an ongoing study with 52 healthy runners (35 RFS, 17 FFS) and 24 injured runners (14 RFS, 10 FFS) for a total of 76 runners (51 M, 25 F; age34.3±11.4 yrs). Vertical average loadrate (VALR) and vertical instantaneous loadrate (VILR) were obtained while running at 2.68 m/s on an instrumented treadmill. All runners reported 0/10 pain during the assessment. Sagittal plane FA and TA at footstrike were measured from video recording using an open-source program. Positive FA designated RFS. Positive TA was defined as ankle anterior to the knee. Between-group differences were evaluated using paired two-tailed t-tests. Correlation coefficients (r) were computed for FA and TA with VALR and VILR (p=0.05; trend: p =0.10). Results: Healthy RFS - FA and TA were negatively correlated with VALR and VILR. Injured RFS – There was a trend toward negative correlation between TA and both VALR and VILR. Healthy FFS – TA was negatively correlated with both loadrates. Injured FFS – There were no significant correlations. Correlation coefficients, slopes, and p values are presented in Table 1. VALR and VILR were higher in RFS vs FFS runners (56±20 vs 40±10, 69±25 vs 54±12 BW/s, p<0.01), but were not significantly different for healthy vs injured runners (52±19 vs 56±26, 63±21 vs 67±27 BW/s, p=0.4). Conclusion: In contrast to current thought, preliminary results suggest that increasing FA and TA at footstrike are associated with decreasing vertical loadrates. This relationship was strongest for FA in the healthy RFS runners and weakest for FA in both the healthy and injured FFS runners. With increased FA, load attenuation may be due to increased eccentric activity of the tibialis anterior as well as increased knee flexion excursion and eccentric quadriceps activity with increased TA.

Abstract licence: CC BY-NC

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