Landing pattern and vertical loading rates during first attempt of barefoot running in habitual shod runners

There is evidence supporting that habitual barefoot runners are able to disperse impact loading rates by landing pattern modification. Yet, case studies suggested that barefoot running may result in severe running injuries, such as metatarsal and calcaneal stress fractures. Injuries may be due to a difference in biomechanical response between habitual and novice barefoot runners. This study investigated the initial effects of barefoot running in habitual shod runners in terms of landing pattern modification and vertical loading rates. Thirty habitual shod runners (mean age 25.5 ± 5.2 years; 18 men; with a minimum running mileage of 30 km per week for at least one year) ran on an instrumented treadmill at 10 km/h shod and barefoot in a randomized order. Vertical average (VALR) and instantaneous loading rates (VILR) were obtained by established methods. Landing pattern was presented as a ratio between the number of footfalls with a heelstrike and the total step number. Twenty participants demonstrated an automatic transition to a non-heelstrike landing during barefoot running, whereas a mixed landing pattern was observed in 10 participants. Compared to shod running, both VALR and VILR were significantly reduced during barefoot running (p < .021). In the subgroup analysis, VALR for the shod condition was significantly higher than barefoot running, regardless of the landing pattern. VALR for the non-heelstrike pattern during barefoot running was significantly lower than participants with a mixed landing pattern. Conversely, we observed two participants who completely altered their landing patterns, presented high VALR and VILR values. Habitual shod runners presented lower loading rates during barefoot running but their landing pattern transitions were not uniform. Novice barefoot runners with a mixed landing pattern may sustain higher loading rates, compared with those who completely avoided heelstrike pattern. However, a complete landing pattern modification may not guarantee lower loading rates.     

Foot and shoe responsible for majority of soft tissue work in early stance of walking

Soft tissues located throughout the human body are known to perform substantial mechanical work through wobbling and deforming, particularly following foot impacts with the ground. Yet, it is not known which specific tissues in the body are responsible for the majority of the soft tissue work. The purpose of this study was to quantify how much of the soft tissue work after foot contact was due to the foot and shoe, vs. from tissues elsewhere in the body, and how this distribution of work changed with walking speed and slope. We collected ground reaction forces and whole-body kinematics while ten subjects walked at five speeds (0.8–1.6 m/s) and on seven different slopes (9 degrees downhill to 9 degrees uphill). Using a previously-published Energy-Accounting analysis, we found that the majority of the soft tissue work during early stance was due to deformation of the foot and shoe. The percentage of work did not vary significantly with speed but did vary significantly with slope. The foot and shoe were responsible for ∼60–70% of the soft tissue work during level and uphill walking, and 80–90% during downhill walking.