RESUMO
The goal of this study was to investigate whole-body kinematic adaptations when running on an unstable, irregular, and compliant surface in comparison to running on asphalt. We hypothesised that the gait pattern (H1) and its stride-to-stride variability (H2) would be affected by the unstable surface but that variability related to some movement features would be reduced over multiple testing days indicative of gait optimisation (H3). Fifteen runners ran on a woodchip and asphalt track on five testing days while their whole-body movements were captured using inertial motion capture and examined using joint angle and principal component analysis. Joint angles and stride-to-stride variability in eight principal running movements were subjected to surface by day analyses of variance. The woodchip track compared to asphalt resulted in (H1) a more crouched gait pattern including more leg flexion and forward trunk lean and (H2) higher stride-to-stride variability in most investigated principal running movements. However, (H3) stride-to-stride variability did not systematically change over testing days. Running on an unstable, irregular, and more compliant surface leads to the adoption a gait pattern and control strategy that are more robust against disturbances caused by the surface but may pose certain risks for overuse injury in trail runners.
RESUMO
The use of orthotic heel lifts is proposed in many cases of Achilles tendon disorders as a first-line or conservative treatment. The use of heeled shoes induces a plantar flexion of the ankle joint with a consequent decrease in the tension forces acting onto the triceps surae. The question to address is how high must the heel be? Gait cycle using 1 cm- and 2 cm-high heel lifts was examined. Each measurement included kinetic and kinematic data on angular variation and moments and power at the hip, knee and foot. The study included 14 healthy subjects (5 males, 9 females) between 20 and 35 years of age. The data provided by the analysis of the force plate curve showed a statistically significant change in some parameters (plate forces, knee moments) which were deemed useful in the analysis of load transfer modalities. A very significant decrease (p=0.0001) was found in the amplitude of the curve expressing the force produced by the whole limb in response to ground reaction forces. This is expressed by a decrease in minimum values, suggesting a lower degree of energy absorption at heel strike, as well as maximum values reflecting the amount of energy generated at push off. This might suggest that by reducing energy absorption by the whole limb a 2-cm heel lift would have a protective effect for those muscles that are most significantly involved in this function, such as the tibiotarsal complex (triceps surae) and the knee complex (rectus femoris).
