Fatigue and pacing in rugby league players

Abstract

Players from a number of team sports such as soccer, Australian rules football, and rugby league adopt pacing strategies during match-play in order to successfully complete match tasks without causing the failure of any single physiological system. Whilst these pacing strategies are influenced by numerous factors, it is currently unclear how physical qualities, physical contact, and time between matches influence pacing strategies. Given the frequency of physical collisions during match-play and the close link between physical qualities and success in rugby league, it is important to determine the impact they have on running intensities and pacing strategies employed by players. In addition, when players have little time to recover between matches, such as during a tournament, they may alter their pacing strategies to manage the fatigue that could occur across the period of congested fixtures. The demanding nature of competition results in players experiencing perceptual and physical fatigue that persists for a number of days following rugby league competition. Although the time course of the fatigue responses are well understood, little is known as to how fatigue impacts match activities and whether the fatigue response can be modified. Previous research has shown positive correlations between physical contact and markers of muscle damage; however as collisions make up a large proportion of the game, further work is required to determine the true cause and effect of physical contact. Although post-match fatigue is inevitable, various recovery interventions (e.g. ice baths, active recovery, compression garments) are often employed in an attempt to accelerate the recovery process. Despite this, the efficacy of many of these strategies has often been questioned. Given that well-developed physical qualities are associated with reduced transient fatigue and can be easily improved via training, it would appear important to determine the impact various physical qualities have on the fatigue response to match-play. With this in mind, the overall aims of this thesis were to determine the impact of physical contact, physical qualities, and periods of congested fixtures on pacing strategies and markers of fatigue and muscle damage in rugby league players. The thesis comprised 9 individual studies divided into two separate, yet interlinking themes. The first theme focused on player workloads, pacing strategies, and match intensities; the second on the fatigue response to these physical demands. Studies 1-3 investigated the influence of contact on subsequent running performance as well as the relationship with aerobic fitness and strength qualities. We found that performing contact within small-sided games leads to greater reductions in running performance as players employ a pacing strategy that prioritises the maintenance of contact efforts over running efforts. Increasing the contact demands leads to further reductions in running intensities. Subsequent studies also confirmed these findings, highlighting that there were greater reductions in running intensities during small-sided games following contact dominant repeated-effort activity as opposed to following running dominant activity. In Theme 2, we investigated the impact of physical contact on fatigue and muscle damage. The addition of physical contact to small-sided games resulted in upper-body fatigue as well as larger increases in blood creatine kinase compared to following non-contact small-sided games. In addition, we also found that increased running loads resulted in greater lower-body fatigue, whereas increased contact loads lead to increased upper-body fatigue. These data indicate that performing physical contact leads to larger increases in muscle damage and upper-body fatigue compared to exercise involving no contact. Furthermore, the location of fatigue sustained (e.g. upper- or lower-body) is sensitive to the activity performed. In Theme 2 we also investigated the fatigue response during an intensified competition and explored the relationship between fatigue and match activities. Increased creatine kinase, a marker of muscle damage, was related to reductions in match activities. Exploring the relationships between physical fitness, match activities and post-match fatigue response following both single matches and during a tournament provided some interesting results. We found players with well-developed physical qualities had higher work-rates, which could be maintained over a number of games, as well as less post-match fatigue. This suggests that physical qualities offer a protective effect against post-match fatigue.