Participants and methods
napping, morning urination
EVENTS
This study was performed concurrently with the other experiments previously described [A schema of the study protocolIn the free urination protocol, the specific act of urination was separately categorized as pre-sleep, considering its unique occurrence at the end and later part of the day. The time intervals of 11:00–17:00 and 17:00—before pre-sleep were adopted to represent approximately 6-h intervals, equating to a quarter of a 24-h day, capturing the daytime and evening periods, respectively. As no participants urinated during nighttime, the period was designated as “after bed~11.” Consequently, for analyzing morning urination, the timeframe was set until 11:00. When there were multiple urination events, the average value was calculated. Regarding the urine production rate, the volume from a single urination was divided by the time elapsed between urinations to determine the urine production rate per time unit [In addition to the free urination protocol, we utilized and adopted a regular urination protocol experiment by Nakamoto et al. [Sleep time was fixed from 24:00 to 08:00. Identical meals (700 kcal each: 60% carbohydrates, 25% fat, and 15% protein; 3.8 g salt) were provided to participants at 08:00, 13:00, and 18:00. Participants consumed a total of 25 ml/kg body weight of water per day in doses given every 2 h between 08:00 and 24:00. Not required to follow a strict daily routine, but to avoid extreme measurements, participants were discouraged from strenuous exercise or napping. The exclusion criteria for this study were the presence of sleep disturbances as measured by the Pittsburgh Sleep Quality Index (PSQI) [