Sex Differences in Endurance Running.

In recent years, there has been a significant expansion in female participation in endurance (road and trail) running. The often reported sex differences in maximal oxygen uptake (VO2max) are not the only differences between sexes during prolonged running. The aim of this narrative review was thus to discuss sex differences in running biomechanics, economy (both in fatigue and non-fatigue conditions), substrate utilization, muscle tissue characteristics (including ultrastructural muscle damage), neuromuscular fatigue, thermoregulation and pacing strategies. Although males and females do not differ in terms of running economy or endurance (i.e. percentage VO2max sustained), sex-specificities exist in running biomechanics (e.g. females have greater non-sagittal hip and knee joint motion compared to males) that can be partly explained by anatomical (e.g. wider pelvis, larger femur-tibia angle, shorter lower limb length relative to total height in females) differences. Compared to males, females also show greater proportional area of type I fibres, are more able to use fatty acids and preserve carbohydrates during prolonged exercise, demonstrate a more even pacing strategy and less fatigue following endurance running exercise. These differences confer an advantage to females in ultra-endurance performance, but other factors (e.g. lower O2 carrying capacity, greater body fat percentage) counterbalance these potential advantages, making females outperforming males a rare exception. The present literature review also highlights the lack of sex comparison in studies investigating running biomechanics in fatigue conditions and during the recovery process.

Neuromechanical adaptations to slippery sport shoes.

Although shoe friction has been widely studied in occupational ergonomics, information was lacking about friction in sport shoes. The purpose of the study was to examine the neuromechanical adaptations to different shoe-surface interface in an aerobic-gym specific movement. Sixteen females performed 10 change of direction movements in two shoe conditions differing by their outsoles (ethyl-vinyl-acetate: EVA and rubber: RB) to ensure significant differences in mechanical coefficients of friction (EVA = 0.73 ±â€¯0.07 and RB = 1.46 ±â€¯0.15). The kinematics, kinetics and muscle activities of the right lower-limb were analysed. Statistical parametric mapping was used to investigate the kinematics and kinetics adaptation to the different shoe-surface coefficients of friction. The participants had a longer stance duration in the EVA compared to the RB condition (526 ±â€¯160 ms vs. 430 ±â€¯151 ms, p < .001). The ankle and knee joints powers and works were lower during both the braking and the push-off phases in the EVA as compared to the RB condition. Preactivation of the agonist muscles (soleus, gastrocnemius medialis and vastus medialis) decreased in the EVA compared to the RB condition (-28.5%, -26.5% and -49.0%, respectively). Performing a change of direction movement with slippery shoes reduced the ankle and knee joints loadings, but impaired the stretch-shortening cycle performance. Participants demonstrated thus a different neuromechanical strategy to control their movement which was associated with a reduced performance.