The Impact of Sleep Restriction on Physical Performance, Markers of Muscle Damage, Inflammation, and Brain-derived Neurotrophic Factor (BDNF) Levels in Female Soccer Players.

Before commencing experimental sessions, the menstrual cycles of the participants will be assessed using a menstrual diary spanning three months before the sessions. Additionally, each athlete will be asked to complete a questionnaire for screening sleep disorders (PSQI) and a chronotype classification questionnaire (MEQ). The average sleep duration over five consecutive nights will be measured using actigraphy; this analysis will determine the length of sleep allocated during experimental sessions. Sleep-related parameters will be recorded using an actigraph (MotionWatch8) and confirmed using the Karolinska Sleep Diary (KSD).

The project involves two experimental sessions (each spanning two days) under two different conditions: a) normal sleep (NS; habitual sleep duration determined from the analysis of five consecutive nights) and b) restricted sleep (RS; sleep reduced by 3 hours during the nocturnal period compared to NS). Participants will perform a simulation match-play game (SAFT90) before NS and RS, followed by performance tests on the following day. Blood samples will be collected at three-time points: a) pre-training, b) post-training, and c) before morning tests on the second day of the experiment. Biochemical analysis of the blood will include progesterone and estradiol (for menstrual cycle analysis) as well as parameters related to muscle damage, inflammatory state, and stress levels (TNF-α; IL-6; CRP; myoglobin; hematology; cortisol; testosterone). Additionally, the level of brain-derived neurotrophic factor (BDNF) will be analyzed.

Day 1 of the experiment: Immediately before training, the first blood collection (8 ml) will occur to analyze the necessary blood biochemical parameters. Subsequently, athletes will undergo a standardized afternoon training session, including a simulation match-play game (SAFT90). Another blood sample will be taken immediately after the exercise. Participants will be asked to wear an actigraph on their non-dominant wrist and consume dinner according to the provided recommendations. They will be instructed to go to bed according to a specified schedule (NS or RS). Additionally, participants will be instructed to spend the time before bedtime engaged in routine evening activities (excluding stimulants like coffee or additional exercise). Participants with restricted sleep will also be requested to report their activities every 30 minutes until they go to bed using an internet communicator.

Day 2 of the experiment: Participants will complete the Karolinska Sleep Diary upon waking up. They will also be asked to abstain from consuming caffeine-containing foods and to have breakfast following the provided recommendations. Before the session begins, participants will complete a readiness to train questionnaire (RTQ) and a mood assessment questionnaire (POMS). Blood samples will be collected, followed by specific football-related performance tests: a) repeated high-intensity effort capacity (Yo-Yo test); b) lower limb power (vertical jump); c) maximal acceleration (3x30 m sprints); d) agility with and without the ball (Zig-Zag Test). Immediately after the performance tests, participants will indicate their pain level (Visual Analogue Scale; VAS) and rate their perceived exertion (RPE 6-20).