Gaelic Football is the most popular sport in Ireland and is characterized by irregular changes of pace and high-intensity efforts interspersed with periods of light to moderate intensity activity. Speed, power and aerobic capacity are essential fitness components for optimal performance during match play. A high level of aerobic conditioning is required to generate and maintain power output during repeated high intensity activities. Study 1: Anthropometric, physiological, metabolic and endurance exercise performance were evaluated in club level Gaelic football players (n=15) in response to 2 weeks of low volume short duration high-intensity interval training (LS-HIT) or high volume endurance training (HVET). Six sessions of LS-HIT and HVET induced similar improvements in endurance exercise performance. V̇O2max was increased significantly in the LS-HIT group only. There was no change in running economy or vV̇O2max following LS-HIT or HVET. Study 2: This study compared the effect of 6 weeks of LS-HIT and HVET on anthropometric, physiological, metabolic and performance indices in club level Gaelic football players (n=25). Both groups had a similar significant increase in V̇O2max, vV̇O2max, Wingate anaerobic performance and endurance exercise performance. Running speed and jump performance did not change following LS-HIT and decreased significantly in response to HVET. Study 3: The construct validity and determinants of repeated sprint ability (RSA) tests were evaluated in club and county level Gaelic football players (n=30). The RSA test involving 8 maximal 30 m sprints on a 22.5 sec cycle demonstrated construct validity. The ability to perform repeated sprints has a greater relation to running speed and power and blood lactate levels than indices of endurance performance. Conclusion: LS-HIT is a time efficient strategy to induce aerobic adaptations normally associated with traditional HVET and maintain indices of speed and power in club level Gaelic football players. An RSA test involving 8 x 30 m sprints on a 22.5 sec cycle was superior in county than club level Gaelic football players.