This symposium will highlight changes in factors related to endurance performance during prolonged exercise; describe the determinants of fatigue resistance during such exercise; and discuss how the physiological resilience of athletes might be enhanced. Speaker A will describe how the physiological determinants of endurance performance, namely maximal oxygen uptake, speed/power corresponding to exercise intensity thresholds, and exercise economy/efficiency, change during endurance events. Following this, physiological changes leading to deterioration of endurance performance will be discussed, with particular focus on metabolic-related changes. Speaker B will introduce how lower limbs are impressive in their efficient use and resilience to the thousands of ground impacts during running, with subsequently limited structural and functional defects. The speaker will focus on some key structural factors and neural adjustments that may influence the economy of running and resilience of the muscle-tendon units involved, with emphasis on the unicity of elite Kenyan runners and differences between sexes. Finally, Speaker C will discuss possible interventions to enhance physiological resilience in endurance athletes. These will include training and nutritional strategies, and the influence of different performance level, training background, and sex. This topic is relevant for any practitioner or researcher in the broad topic of endurance exercise.
ECSS Paris 2023: IS-PN01
This talk will introduce the concept of physiological resilience or durability, and highlight its importance as an independent determinant of endurance exercise performance. This can be illustrated through studies on truly elite athletes. For example, in Nike′s ′Breaking 2′ marathon project, measurements of VO2max, fractional utilization of VO2max and running economy in a fresh condition provided reasonably accurate predictions of performance and were used to identify which elite athletes were best equipped physiologically to attempt to break the 2-hour marathon barrier. Of the athletes selected, however, only Eliud Kipchoge has achieved this feat and his performances are exceptional compared to his peers. This suggests that he has superior resilience (i.e., is better able to resist the deterioration of his ‘start-line physiology’ during a marathon) compared to his rivals. Recent studies indicate that not only do physiological variables such as exercise efficiency and critical power deteriorate during prolonged, fatiguing exercise, but the extent of this deterioration is highly variable between individuals (for example, 1-32% for critical power). Moreover, in the field, the degree of uncoupling between heart rate and speed during endurance exercise has been shown to be an important metric of performance. The basis for these differences in neuromuscular fatigability and metabolic stability (including glycogen depletion, metabolite accumulation, and changes in muscle fibre recruitment) will be discussed with comparisons drawn between elite East African runners and their Caucasian counterparts.
Read CV Andrew JonesECSS Paris 2023: IS-PN01
Endurance running is usually defined as a stretch-shortening cycle (SSC) type exercise in which most of the lower limb extensor muscles are optimally pre-activated prior to ground impact and then fully activated during the braking phase to actively resist to their stretch before shortening with rather low muscle activity. The muscle-tendon units of the lower limbs are impressive for their efficient use of the SSC to store and recoil elastic energy, but also for their resilience to the thousands of ground impacts encountered during running, with limited structural and functional defects specifically in SSC-type muscle actions. Over the last 20 years, ultrasound technology has provided new insights into both the efficient and protective role of the tendon and the architectural gear ratio, as well as the lack of stretching of biarticular muscles. Each of these factors can be seen as contributing to the rather limited structural and functional deficits in SSC performance found after a running race. Using this technique, our Japanese colleagues have highlighted the potential role of genetic endowment in the specificity of the muscle-tendon and foot architecture of Kenyan runners. As previous physiological studies have shown no marked specificity in any of the basic physiological parameters of elite East African endurance runners, it was concluded that their particular triceps surae muscle-tendon structure may contribute to their unique muscle activation and economical running pattern, which differs from the classical SSC concept. In recent years, female participation has increased considerably in endurance running. Despite sex differences in muscle-tendon characteristics and running biomechanics, males and females do not differ in terms of running economy, suggesting that both sexes optimise their running patterns to suit their characteristics. An indirect way to study sex differences in resilience is to follow the structural and functional recovery pattern after a race. In recreational runners, females showed more structural deficits in the hamstring muscle group than males, but sex-specific intermuscular compensations occur during SSC tasks that would mask residual dysfunction of some muscles.
Read CV Caroline NicolECSS Paris 2023: IS-PN01
This talk will discuss effective interventions to enhance physiological resilience (or durability), and compare athletes with different characteristics to explore other potential mediators of this phenomenon. The current evidence on training interventions to influence resilience in trained athletes is limited, with strength training and repeated sprints proven to be effective. Specifically, adding strength training to the program of endurance athletes can improve performance at the end of prolonged exercise (by between 4 and 40%), as demonstrated in cycling, running, and cross country skiing. Together with this, a reduced deterioration of running economy or cycling efficiency often occurs. Including short sprints during prolonged exercise may be another strategy to improve performance in a fatigued state, although evidence is limited to a few cycling studies. Longitudinal and cross-sectional studies with trained and elite athletes also suggest that performance level, age, and training background can influence resilience, with higher calibre athletes, who are used to longer endurance sessions, and somewhat older athletes being able to produce superior performance after prolonged exercise, and displaying less pronounced physiological drifts. Dietary interventions can also improve durability, with carbohydrate intake allowing athletes to maintain their fresh critical power (CP) after prolonged cycling compared to placebo. Finally, resilience may be dependent on sex, with female runners demonstrating a lower deterioration of economy during prolonged runs, which may help explain differences in marathon pacing (i.e., typically more even) compared to men. Other interventions such as long runs/rides, due to their specificity, may also be effective. More studies are required to improve our understanding of adaptations leading to improvements in durability in endurance athletes.
Read CV Michele ZaniniECSS Paris 2023: IS-PN01