What’s your typical Saturday look like? Do you sleep in and relax, or are you likely to get up and workout on Saturday? Although Saturday and Sunday are regular holidays in standard schools and offices, the daily rhythms on Saturdays often differ. For example, for children, their latest bedtimes are Friday and Saturday night.
A series of recent investigations studied the association of morningness-eveningness with circadian clock-related genes. Scientists believe the single-nucleotide polymorphism (SNP) in the 3’-flanking region of the CLOCK gene (311 T/C; rs1801260) influences sleep and activity. Studies have reported that the C allele of the rs1801260 is associated with an evening preference.
In addition to that, breakfast hours among C allele carriers were later than those among T carriers among obese adults, particularly during weekends. Unfortunately, they only reported weekly total physical activity (PA) levels. Given that CLOCK genes may regulate daily rest-activity rhythms, the time of day in which PA is performed should be investigated, as well as more information about CLOCK 3111T/C carriers in general.
In this context, under free-living conditions, researchers explored whether or not the presence of this particular polymorphism rs1801260 in the CLOCK gene in young individuals was related to the daily, weekly PA level. PA was objectively measured for at least seven consecutive days using a single-axis electronic accelerometer. Participants were instructed to wear the accelerometer throughout the day except during sleep and water-related activities (e.g. bathing, swimming). They recorded the non-wearing time in their lifestyle log when they did not wear the accelerometer. Also, participants recorded their wake/bedtimes every day during the study period. Results showed that TT carriers had an earlier weekly (7days) wake time and bedtime time than TC+CC carriers.
Furthermore, TT carriers’ wake time and bedtime on Saturday were significantly later than on other days. The daily PA levels on a given day were similar between genotypes. However, the hour-by-hour PA in TT carriers was significantly greater than in TC+CC carriers on Saturday. These data suggest that regardless of the wake and sleep rhythms in a week, the rs1801260 may influence hour-by-hour PA rhythms only on weekends, especially on Saturdays.
In addition, the finding that the PA levels in evening-oriented C allele carriers were only lower than in TT carriers on Saturday suggests that these individuals may use Saturday as a ‘recovery day’ from the week’s accumulated fatigue. Scientists also wonder whether evening-oriented C allele carriers are forced to wake/go to bed earlier than their proper biological clock hours and thus suffer from feeling drained because of academic/social obligations. If you would like to know more about this research, you can read the study here:
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