Investigation of the relationship between training load, monitoring markers of recovery, injury, and illness in elite team sports

Introduction: In elite athletes, the margins between success and failure are very small, and so to optimise performance, reduce the risk of injury and illness, coaches need to prescribe the correct balance between training load and recovery. Each player’s training response will be individual and depend on multiple factors. Therefore, a combination of monitoring markers of recovery are needed to help effectively evaluate a player’s training and recovery response. Aim: The aim of this programme of research was to evaluate the association between monitoring markers of recovery and training load, and to explore the relationship between training load, injury, and illness in elite team sports. Methods: Data were collected over a 10-week pre-season period with elite academy Rugby union players and over an entire soccer season (40 weeks), with elite soccer players. The 10-week pre-season data aimed to investigate the association between subjective and objective markers of recovery (salivary cortisol and adductor squeeze strength) and training load (session rate of perceived exertion; sRPE). Additionally, data were also collected to explore the association between salivary immunoglobulin A (sIgA), upper respiratory tract infection (URTI), and training load (sRPE). The 40-week soccer season data were used to explore the relationship between training load, injury, and illness. Five studies were conducted in this programme of research. Results: Study 1 results showed no significant association between salivary cortisol and subjective markers of recovery or training load in Rugby Union players. However, the findings suggested that salivary cortisol may be an indicator of a player’s physiological stress response, as the results indicated that if a player’s cortisol levels did not return to baseline by the following Monday, after a weekend match, they may not have fully recovered. It was also observed, where salivary cortisol significantly increased on a Friday (weeks 5 and 10), perceived fatigue was also found to significantly increase. Study 2 investigated the association between subjective and objective markers of recovery and training load in Rugby players. The results found adductor squeeze strength significantly associated with perceived fatigue (r=-0.335, R2 =11.2%, p <0.001) and muscle soreness (r=-0.277, R2=7.7%, p <0.001). A weak association was also found between adductor squeeze strength and training load. Study 3 found an increase in week-to-week acute load change (>9%), and exponentially weighted moving averages acute:chronic workload ratio (>1.20), increased the risk of a non-contact injury, while a high 2-week (>4000 AU) and 3- week (>5200 AU) cumulative load increased the risk of a contact injury, in soccer players. Study 4 found where sIgA decreased by 65% or more, a Rugby player was at an increased risk of contracting an URTI within the subsequent 2 weeks. The final study (Study 5), over a 40-week soccer season, found that an increase in 2- and 3-week cumulative load was associated with an increased risk of a player contracting an URTI. Conclusion: The findings of this research highlight that a number of different monitoring markers (subjective and objective), combined with training load, may be used to provide a holistic view of a player’s training response. This programme of research may help coaches to appropriately plan and adjust training, thus optimising the individual and team’s performance and, while reducing the risk of injury and illness.