The role of engineering in fatigue reduction during human locomotion - a review

The purpose of this review is to discuss how an athlete's fatigue can be limited by using recent innovations in sports engineering. The review focuses on human locomotion, i.e. mainly fatigue during endurance sports. First, through a general definition and illustrations of means of locomotion such as running, cycling, walking/hiking or speed skating, several aspects of fatigue reduction will be presented. With regards to the mechanical stress, it has been shown that (i) contrary to 'in vitro' experiments and, in comparison with hard shoes, soft shoes do not appear to reduce impact forces during running and (ii) too much cushioning can have side effects in terms of energy cost and thus in terms of fatigue in running and mountain biking. On the contrary, the equipment weight-that also depends on the weight repartition-may have dramatic effects in terms of fatigue. Any equipment allowing better mechanical efficiency (e.g. chainrings, klapskate) or work distribution (e.g. walking with poles) can potentially reduce an athlete's fatigue under similar conditions without this equipment. However, among elite athletes, the use of technical innovation does not seem to affect fatigue per se but provides performance improvement with similar fatigue occurrence. It appears that fatigue-related improvements caused by technical innovations only occur among sportsmen exercising for leisure. In the second part of this review, recent textile innovations aimed at decreasing fatigue by the use of elastic compression stockings or at regulating temperature will be discussed. Finally, two methods designed to improve recovery after training or competition (elastic compression and electromyostimulation) will be discussed. Both these techniques are widely used by elite athletes despite relatively poor scientific evidence of their efficiency, with the exception of recovery after eccentric exercise.