NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- Injuries are of widespread concern to professional sporting organisations, sport and recreation groups and individual athletes. In particular, injuries have a profoundly negative effect on many aspects of human physiology and implications range from long-term health issues to financial ramifications in elite team sport. Injuries in running-based team sports, including the Australian Football League, have been scrutinised in the past 20 years, with previous research examining certain risk factors associated with injuries, however, many are considered as non-modifiable. Injury prevention strategies are required to identify, modify and minimise the impact of modifiable and intrinsic risk factors. One such modifiable risk factor that has recently received attention due to its reported links to soft-tissue non-contact injuries is vertical stiffness. The aim of this project was to conduct a series of studies investigating the role of stiffness in injuries in Australian footballers, and to examine a novel method of modifying this neuromechanical variable.
Study one determined the acute seasonal changes of stiffness in Australian footballers and examined the relationship with non-contact, in-season, soft-tissue injuries. No significant differences were recorded for bilateral vertical stiffness between the injured and non-injured groups throughout the season. When assessing vertical stiffness asymmetry, the injured group displayed a significantly higher value than the non-injured group at the end of the pre-season. This information can be used by medical and conditioning staff as an injury prevention method and player screening protocol. Furthermore, given these results, intervention strategies to modify stiffness require investigation.
The role of stiffness in athletic performance has been documented, and to date, it appears that a stiffer muscle-tendon complex is advantageous to athletic performance, however, stiffness that is too high or too low may be linked to an elevated risk of soft-tissue injury. Whilst training interventions to increase stiffness have been investigated, few have focused on reducing stiffness in the lower-body. Hence, study two examined the efficacy of a novel training intervention, aqua plyometrics, to reduce stiffness without negatively affecting athletic performance. There were no significant changes to stiffness recorded, however, athletic abilities and jump performance significantly increased. Improvements to athletic performance in the absence of changes to stiffness will be of particular interest to exercise practitioners, conditioning coaches and medical staff for assessing, monitoring and managing stiffness in Australian football players and other team sport athletes.