The study's sample population will comprise all athletes who will be members of the Turkish national sitting volleyball team in the 2026 season. The selection of participants will be carried out using a purposive sampling method, and data will be collected from all volunteers who will be willing to participate in the study and who will meet the specified criteria. This approach will result in the establishment of a sample group that will reflect the full characteristics of the target population.

The method of this study will consist of a mixed-method design conducted with athletes selected from the Turkish Women's National Sitting Volleyball Team through purposive sampling. The Pittsburgh Sleep Quality Index (PSQI) will be used to assess participants' sleep quality, while the Athlete Sleep Behavior Questionnaire (ASBQ) will be employed to evaluate their sleep behaviours. Data will be collected at two distinct time points: first, prior to the implementation of a structured sleep hygiene education program, and subsequently approximately 30 days later, designated as the post-test phase.

In order to provide a more in-depth explanation of the results obtained from the quantitative data and to achieve a more contextual understanding, qualitative data will be collected through two online focus group discussions conducted following the post-test.

Measurement Tool: The ASBQ is a 17-item five-point Likert-type questionnaire used to assess athletes' sleep habits. This tool identifies abnormal patterns and areas for improvement in an athletic context.

This scale allows athletes to evaluate their own sleep behavior through self-assessment.

Scoring Interpretation: The scale is evaluated based on the total score. A total score of 34 or below indicates "good sleep behavior," while a total score of 40 or above indicates "poor sleep behavior."

Unit of Measure: Total Score on the ASBQ (Range: 17 to 85).

The PSQI is a self-rated questionnaire that assesses sleep quality and disturbances over a 1-month time interval. It consists of 19 individual items that generate seven distinct component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. Each component score is weighted equally on a scale from 0 to 3. These seven component scores are then summed to yield a single global PSQI score, which has a possible range of 0 to 21. A global score of 5 or less indicates "good sleep quality," while a score greater than 5 indicates "poor sleep quality." Therefore, higher global scores represent worse sleep quality and greater sleep difficulties.

Unit of Measure: Global Score (Range: 0 to 21)

To complement the quantitative findings within a mixed-methods design, qualitative data will be collected through online focus group discussions. These sessions will utilize semi-structured interview guides specifically designed to explore participants' underlying sleep habits, their behavioral changes post-intervention, and their overall perceptions of sleep hygiene. The qualitative data (transcripts) will be subjected to thematic analysis to identify recurring patterns, context, and relationships. Unlike quantitative measures, this assessment does not yield a numerical score; instead, it generates descriptive narrative themes that evaluate the real-world effectiveness and subjective experience of the training program.

Unit of Measure: Qualitative Themes and Narrative Feedback (Descriptive/Categorical)

Social Jetlag (SJL) quantifies the misalignment between an individual's biological circadian clock and their social or work schedules. It is determined by calculating the absolute difference between the mid-point of sleep on free days (MSF) and the mid-point of sleep on workdays (MSW). The mid-point of sleep is defined as the exact halfway point between sleep onset and wake time (e.g., if sleep onset is 24:00 and wake time is 08:00, the mid-point is 04:00). The specific calculation formula used is:Social Jetlag is calculated based on the difference between the mid-point of sleep on free days (MSF) and the mid-point of sleep on workdays (MSW). The calculation formula is as follows: SJL = |MSF - MSW|.

Unit of Measure: Time difference (Expressed in Hours and Minutes)