A randomized, two-trial (placebo vs. supplement consumption), cross-over, double-blind, repeated measures design will be applied to study i) the performance, metabolic and inflammatory overload of overtime in soccer and ii) how carbohydrate supplementation affects recovery following a football match with overtime. The study will be performed during a brake of the in-season period to mimic a real life setting. A 10-day washout period will be utilized between trials.

Initially and before the familiarization period, measurement of descriptive variables will be performed: body composition, maximal oxygen consumption, football-specific endurance via YO-YO IE2 and IR2, technical performance, daily diet intake, resting metabolic rate (canopy method), and daily physical activity (IPAQ questionnaire). At this time, volunteers (of equal technical, tactical and physical potential) will be randomly assigned (equally representing all field positions) to two teams.

A 7-day familiarization period will be applied initially during which participants will be accustomed with research procedures, match tactics, and diet (a standard diet will be given based on their dietary analysis, RMR measurement and daily energy expenditure). During this adaptive period, volunteers will participated in light training aimed at developing team cohesion.

Thereafter, the two experimental trials will take place. Each trial will include administration of either a high carbohydrate diet (CHO trial) or standard diet (control trial) and they will be carried out in a random order for each participant. Each trial will included two 120-min matches (M1 and M2) performed 3 days apart according to UEFA official schedules for National teams' tournaments. On match days, volunteers will participate only in morning testing sessions but not practice. Prior to each game, a standard breakfast and meal will be consumed. During each match, players will be allowed to drink only water ad libitum and their water intake will be recorded. Sweat loss during the match will be determined by measuring players' body mass wearing dry shorts immediately before the match, at half time, immediately after the match and immediately after each half of the overtime. Two practice sessions will take place on days 1 and 2 between M1 and M2 designed according to the training model routinely adapted by national football teams during the UEFA EURO tournament. Matches will be organized according to official UEFA regulations. Field activity during matches and practices will be recorded using high time-resolution GPS instrumentation and heart rate monitoring. Following M1 and for the next 3 days until M2, participants will receive either carbohydrate or placebo. Diet intake will be monitored daily throughout the study.

Performance assessments will be performed post-matches and daily between matches.

Blood samples will be collected at baseline as well as at 90 and 120 min of each match and before M2.

Muscle biopsies will be collected at baseline as well as at 90 and 120 min of M1 and before M2.

Inclusion Criteria:

• competitive level for ≥4 years (≥5 training sessions/week, ≥1 match/week)
• no recent history of febrile illness, muscle lesions, lower limb trauma, and metabolic diseases
• no use of ergogenic supplements and medication (for ≥6 prior to the study)
• non-smokers

Exclusion Criteria:

• recent history of febrile illness, muscle lesions, lower limb trauma, and metabolic diseases
• use of ergogenic supplements and medication (for ≥6 prior to the study)
• smoking
• competitive level for < 4 years