Limited data exists on a transition process of minimalist shoe running, warranting longitudinally designed studies. The primary aim of this study was thus to determine whether lower limb kinematics can be adapted, whether vertical average loading rate (VALR) can be attenuated, and whether lower limb joint moments can be altered by either novice or short-term (seven-week) minimalist shoe training.
Ten experimental (EXP) habitually shod male endurance runners (age 24.10 ± 1.74; weekly training mileage 29.36 ± 8.51 km; BMI: 22.83 ± 8.55 kg/m2) volunteered to participate in a seven-week minimalist shoe transition programme. Eleven age and training matched control participants (CONT) (age 24.00 ± 2.18; weekly training mileage 24.90 ± 3.30 km; BMI: 23.78 ± 6.12) continued to run in their usual running shoes during the intervention period. All participants were provided with a pair of Vibram Fivefingers ® (VF). The VF intervention started at ~ 11% to 22% and ended at ~ 52% to 132% of the participants‘ usual shod training distance, determined by subjective lower limb comfort ratings.
Lower limb biomechanics for barefoot: BF, minimalist: VF, and shod: SH were recorded with an eight-camera Vicon ® motion capture system, synchronized with a Bertec ® force plate, both prior to and after the transition programme. Twelve running trials at self-selected speeds were recorded bilaterally for each shoe condition. An inverse dynamic approach was used to calculate lower extremity joint moments. Primary parameters of interest were kinematic: step frequency (steps/min), step length (m), footstrike angles (FSA, degrees), strike index (SI,%); average vertical loading rate (VALR, BW/S) and sagittal and frontal plane peak joint moments (Nm/kg.m) of the ankle, knee and hip.
At pre-testing, the results showed that for VALR, VF running was significantly higher than SH running but significantly lower than BF running (P < 0.05). Statistically significant shorter step lengths, higher step frequencies, greater plantar-flexion FSA, higher strike index, greater knee flexion FSA, and greater ankle inversion FSA were seen in BF and VF conditions compared to SH (P < 0.05). Statistically higher plantarflexion moment peak (PFM) while lower ankle dorsiflexion moment peak (DFM) and knee abduction moment peak (KAM) was found while BF and VF than SH running.
The only statistically significant effect of the VF training intervention on kinematics was that of higher step frequency for the SH condition (P < 0.05), and greater inversion FSA in the BF condition. A trend was seen for the EXP group to increase VALR (P > 0.05). Ankle PFM peak significantly increased, while knee extensor moment peak (KEM) peak significantly decreased for the EXP group only (P < 0.05).
Contrary to the initial hypothesis, novice or short-term VF training did not result in significantly attenuated VALR. However, alterations in joint moments suggest a shift in the distribution of external loads due to the VF training. Insufficient kinematic adaptation with VF training could be attributed to inability to sense higher VALR or due to greater perceived ratings of calf-Achilles discomfort, and may indicate that more than seven-weeks are required to transition and adapt to VF running.
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