According to a new study, exercise could help you shift your body clock forward or backward depending on whether you do it in the morning/afternoon or in the evening. This finding could help people cope with disruptions to the body’s internal clock like jet lag or shift work.
The team found that exercising at 7am or between 1pm and 4pm shifted the body clock to an earlier time, while doing exercise between 7pm and 10pm delayed it. Exercising in the middle of the night (1am to 4am) or mid-morning (10am) had little effect. The findings are reported in The Journal of Physiology.
Our body clock, or circadian rhythm, is the 24-hour cycle of the many physiological processes that regulate when we are hungry, sleepy, and so on. This cycle depends on both internal and external factors. Exercise has long been thought to be involved, but its exact role has remained unclear. This study helps to answer this question, although, given the fact that the participants were active people, the findings might not translate to the average person.
"Exercise has been known to cause changes to our body clock. We were able to clearly show in this study when exercise delays the body clock and when it advances it," lead author Professor Shawn Youngstedt, from Arizona State University (ASU), said in a statement. "This is the first study to compare exercise's effects on the body clock, and could open up the possibility of using exercise to help counter the negative effects of jet lag and shift work."
The team, from ASU and the University of California, San Diego, examined the body clock of 101 participants for up to 5.5 days after they'd exercised. They measured levels of melatonin in the volunteers' urine and used the hormone's peak to determine the body clock's baseline timing.
Once that was established, participants ran or walked on a treadmill for an hour during a particular time slot for three consecutive days. After the third session, the team re-assessed each participant's body clock and looked for any shifts from the baseline.
The team plans to continue to investigate this further. They are curious to find out more about the intensity of exercise's impact on the circadian cycle and determine whether the shift can be increased and decreased by combining exercise with exposure to bright lights or melatonin.