Stride parameters in endurance runners

A It is commonly thought that athletes automatically adapt to a simple, natural and cyclical action, such as running, and that any increases in performance level are almost entirely due to improvements of the conditional capacity and metabolic systems. The importance of mechanical and co-ordinative attributes and the possibilities for conserving movement and re-utilising elastic energy deriving from the eccentric contraction movements have rarely been explored and have never been a focal point of research in endurance sports. This study included 61 male and female longdistance runners, 31 of whom performed at a national/international level and 30 of whom were amateur level competitors. In periodic tests conducted for functional evaluations, video recordings were made of the athletes’ running movements at different speeds. Several kinematic parameters were analysed. The statistical results, behavioural analysis and individual adaptations obtained are useful for elaborating and proposing methodological elements in training for correcting and perfecting distance running technique. tinguishing the disciplines, it becomes more difficult to isolate and define each specialty. In the sports literature, endurance running is classified among the cyclical aerobic specialties with low co-ordination and technical content. VERCHOSSHANSKJ (2001), for example, stated: “the composition of cyclical movements (that require the development of endurance) seems to be simpler than that of acyclic locomotion”. The opinions and studies published so far, for example McARDLE et al. (1996), reinforce the idea that each athlete automatically adapts to a simple, natural and repetitive movement, like that of running, and that improvements in performance are entirely related to the improvement of conditional abilities and metabolic implications: “An exercise that can be performed for a prolonged period of time is relatively simple from a mechanical standpoint, since the gesture is repeated from the beginning to the end; the movements – some of which were learned in childhood are completely automatic and racing strategy is relatively simple. it’s pretty evident that in these situations the nervous and psychological factors are much less important than the physical, physiological and biomechanical ones” (SAIBENE et al., 1986). Although various studies have shown that mechanical efficiency is the component that differentiates elite athletes (among themselves) in endurance running, even these studies continue to hint that an individual athlete’s running technique cannot be effectively modified to produce a significant result and that, at any rate, adaptations are consequences of bio-structural and metabolic modifications that occur during training. Furthermore, when biomechanical parameters were taken into consideration, the results and observations made by experts lead to conclusions that are diametrically opposed. FORTNER (2006), after a lengthy observation of the rhythmic behaviour of the first three finishers at the 1999 New York Marathon (Kagwe, Chebe and Bayo), noted that the winner “adopted a longer stride (at the same speed) as opposed to a greater frequency”. NOAKES (2001), citing other authors (MORGAN, 1995 and NELSON & GREGOR, 1976), states: ”through training, athletes lengthen their stride and reduce frequency. Some researchers maintain that this optimises running economy because the increased stride length is more economical than an increase in frequency”. On the other hand, McARDLE et al. (1996) claim that: “it generally costs more to lengthen one’s stride than it does to shorten it” and VITTORI (1997) states: “There is no doubt that the energetic cost required to maintain the same speed is greater for a long stride than it is for a shorter stride at a higher frequency. it costs more to create length than it does to create frequency”. According to CAVANAGH & WILLIAMS (1982), athletes themselves automatically choose the best speed and any attempt at modifying the stride length or stride frequency “produces a negative effect on the mechanical efficiency”. Within the study conducted in an attempt to establish the best individual energetic cost by way of a variation in stride frequency and stride length at a given speed there exists a conceptual error that excludes all results except those obtained: modifying a “spontaneous” movement by way of any voluntary intervention produces the effect of increasing energy expenditure. The question that we might pose at this point is: are we absolutely certain that an athlete is able, always and in any circumstance, to match his/her motor potential to the technical and mechanical parameters of endurance running in an automatic and instinctive manner? More precisely, can the work of the middleand long-distance coach (on a level with the trainers of any other specialty or discipline) be targeted towards modifying the characteristics and technical, rhythmical and mechanical running abilities of an individual athlete? 42 Ne w St ud ies in A th let ics • n o. 4/ 20 07 Stride parameters in endurance runners