Ingesting carbohydrate (CHO) before and during prolonged steady-state exercise can significantly improve the endurance capacity (time to exhaustion) of adolescents. This knowledge, combined with current understanding of the physiological and metabolic responses of young people to prolonged steadystate exercise, as well as awareness of youth team games participation statistics, suggests CHO ingestion before and during team games exercise may be beneficial for adolescent team games players. However, research in this area has not been conducted, presenting a notable gap in the paediatric exercise science literature. This thesis described three studies with the aim of investigating the influence of CHO ingestion immediately before, and during, prolonged intermittent, high-intensity exercise on the endurance capacity, sprint performance, and physiological responses of adolescent team games players. The studies investigated a CHO-electrolyte (CHO-E) solution, solutions of differing CHO concentration ([CHO]), and CHO in the form of a gel in trained 12-14 year old soccer, rugby, and field hockey players during a modified Loughborough Intermittent Shuttle Test (LIST). Study 1 (n = 15) reported a significant 24.4% enhancement of intermittent endurance capacity with ingestion of a 6% CHO-E solution compared with a placebo (PLA, 5.1 ± 1.8 vs. 4.1 ± 1.6 min, P < 0.05, r = 0.51), with distance covered also significantly greater in the CHO trial (851 ± 365 vs. 694 ± 278 m, P < 0.05, r = 0.52). No significant influence of CHO was found for mean sprint times (P = 0.35, r = 0.27) or physiological response except at exhaustion, where peak heart rate was significantly greater in the CHO trial (P < 0.05, r = 0.55). Study two (n = 7) found a significant influence of [CHO] on intermittent endurance capacity, with a 6% solution increasing intermittent endurance capacity by 34.1% compared with a 10% solution (5.5 ± 0.8 vs. 4.1 ± 1.5 min, P < 0.05, r = 0.76). No significant difference was observed between the 2% (4.8 ± 1.2 min) and the 6% (P = 0.10, r = 0.63), or the 2% and the 10% (P = 0.09, r = 0.63) solution. Distance covered was significantly greater with the 6% solution compared with the 10% solution (931 ± 172 vs. 706 ± 272 m, P < 0.05, r = 0.76), but was not significantly different compared with the 2% solution (811 ± 230 m, P = 0.09, r = 0.63) or between the 2% and 10% solutions (P = 0.11, r = 0.61). Carbohydrate concentration did not significantly influence mean sprint times (P = 0.38, r = 0.42) or physiological response. Study three (n = 11) reported a significant 21.1% enhancement in intermittent endurance capacity with ingestion of a CHO gel, isoenergetic to the 6% CHO-E solution used in studies 1 and 2, compared with a PLA gel (4.6 ± 2.0 vs. 3.8 ± 2.4 min, P < 0.05, r = 0.67). Distance covered was also significantly greater in the CHO trial (787 ± 319 vs. 669 ± 424 m, P < 0.05, r = 0.57). No influence of the CHO gel was observed on mean sprint times (P = 0.33, r = 0.31) or physiological response. This thesis reports a significant positive influence of CHO ingestion on the intermittent endurance capacity of adolescent team games players during prolonged intermittent, high-intensity exercise. Ingestion of a 6% CHO-E solution was more beneficial than a PLA solution and a 10% CHO-E solution. When compared to a PLA gel, CHO gel ingestion was analogous in efficacy to a 6% CHO-E solution. Carbohydrate ingestion did not significantly influence sprint performance. The influence of CHO on the physiological responses of adolescent team games players to prolonged intermittent, high-intensity exercise was minimal, with the only reported effect being a significantly greater HR at exhaustion in study 1. This thesis has provided evidence to support the use of CHO before and during team games in adolescent team games players, begun to formulate guidelines for CHO ingestion by adolescent team games players, and provided a robust foundation for further study in this field.