The aims of the study are:

1. To examine skeletal muscle and blood metabolites during an official basketball game and to relate those to skeletal muscle performance during and after the game.
2. To investigate whether skeletal muscle and blood metabolites are related to game-induced fatigue.
3. To relate field activity during a basketball game with the responses of skeletal muscle and blood metabolites.
4. To investigate how blood lactate reflects muscle lactate concentration during a basketball game.
5. To determine whether temporary fatigue develops during a basketball game. game.

The basketball players will participate in three experimental games (N = 10/game) on an indoors basketball stadium. During a 2-week familiarization period, volunteers will be familiarized with the experimental procedures and participate in very light training (at local basketball facilities) aimed at developing match tactics and team cohesion. At the end of the familiarization period and before the experimental game, participants will undergo a 3-day baseline performance testing (resting conditions) at University (Department of Physical Education and Sport Sciences, University of Thessaly) facilities. Prior to the games, the players will refrain from strenuous exercise and intake of alcohol for 48 hours and from tobacco and caffeine for 12 h. Dietary intake will be monitored with daily diet recalls for 7 days before the experimental period and will be standardized for all participants by a registered dietitian. The dietitian will also prescribe the meals and snacks on the game-day. On the day of the game, participants will arrive at the stadium 1.5 h before for resting skeletal muscle and blood sampling. For the first muscle biopsy and in preparation for later obtainment of biopsies from vastus lateralis muscle. An incision will be made under local anesthesia (20 mg/ml xylocaine without adrenalin) and covered by sterile band-aid strips and a thigh and shoulder bandages. In addition, an inertial measurement unit (IMU) and a heart rate monitor will be placed on each subject. During the match, a number of physiological measurements will be performed at fixed times (before the game, at half-time and post-match) and after intense exercise periods within the four 10-min periods of the game. Volunteers will be randomly assigned, using the sealed envelope procedure, in six teams representing all field positions and each team will play in one of three experimental games (random allocation using standard procedures) against each other in a full 40-minute game according to official regulations. A total of 10 additional players (from various playing positions) will serve as substitute players that could enter the pitch for a few minutes when a player will have to leave the court (either participate in measurements or will have completed it's pre-determined playing time or in case of an injury). Fifteen players (pre/post game measurement group) will have muscle and blood samples taken at rest, at the end of the 2nd period (half-time) and at the end of the 4th period (end of game). A second group of eight players (intense periods measurement group 1) will have muscle and blood samples collected at rest and during the first and third period of the game (immediately after an intense period of game-play). A third group of seven players (intense periods measurement group 1) will have muscle and blood samples collected at rest and during the second and fourth period of the game (immediately after an intense period of game-play). An intense exercise period of game-play is identified as a period with a heart rate of > 90% of maximal [as assessed by the maximal heart rate obtained during a graded exercise test to measure the maximal oxygen consumption (VO2max)], a high number of high-intensity runs (speed of > 18 km/h), sprints (speed of > 25 km/h) and/or jumps evaluated by a professional licensed coach. All muscle biopsies will be sampled from the vastus lateralis. All players will have their field activity and heart rate measured throughout the game using IMU units and heart rate monitors. Games will start at 17.00 - 18 p.m. to avoid diurnal variations and will be held under normal environmental conditions. A standardized 30-min warm-up period will be performed before each game. All games will be videotaped.

Inclusion Criteria:

• Health status: were free of recent musculoskeletal injuries and/or illnesses (≥ 8 months before the study).
• Not consuming ergogenic supplements/medications (≥ 6 months before the study)
• Not smokers

Exclusion Criteria:

• Completion of the pre-determined participation time during the experimental game.
• Completion of all field measurements.
• Completion of all pre-determined sampling points for biological tissue.