Daylight saving time begins on Sunday, March 10, 2024, at 2 A.M. local time in most U.S. states, forcing clocks forward by an hour. This annual shift isn’t just a minor inconvenience; research links it to increased hospital admissions, sleep loss, and worsening of sleep disorders and depression. The sudden disruption to our internal clocks, known as circadian rhythms, has real health consequences.
The Science of Internal Clocks
Our bodies operate on a 24-hour cycle governed by the suprachiasmatic nucleus (SCN), a tiny but crucial cluster of cells in the brain. The SCN acts as the “master clock,” coordinating timekeeping in almost every cell through peripheral clocks in organs like muscles, lungs, and kidneys. These cells regulate vital functions such as digestion and energy levels.
The Power of Light and Exercise
Scientists have found that combining morning sunlight exposure with physical activity is the most effective way to stabilize circadian rhythms after the time change. Light activates the SCN, while exercise powerfully cues peripheral clocks in oxygen-sensing organs. This dual approach shifts internal clocks more efficiently than either method alone.
Study Findings
A small study at Arizona State University found that participants who exercised in the morning sunlight experienced a larger shift in their internal clock timing than those who exercised or had light exposure independently. While larger studies are needed, the evidence suggests exercise has a significant impact on adjusting to time shifts.
How to Prepare for the Shift
Experts recommend easing into the transition a few days beforehand:
- Wake up 15–20 minutes earlier each day starting March 5th.
- Go for an outdoor walk or jog one hour after waking up. (Indoor light is usually not bright enough to reset internal clocks.)
- Exercise at 50–75% of full exertion. (Get slightly out of breath.)
This gradual approach minimizes the shock to your system. Older adults and those with chronic illnesses should be especially diligent, as circadian rhythms lose flexibility with age.
Avoid Counterproductive Habits
Certain behaviors can undermine the benefits of light and exercise:
- Late-night eating or exposure to bright light can delay rhythms.
- Inconsistency is the enemy of a stable circadian cycle.
Long-Term Benefits
Once you’ve adjusted, don’t abandon the habit. Maintaining a regular light-and-exercise routine is essential for long-term health, reducing the risk of chronic diseases and premature death. The more body parts you engage through exercise, the more effective it will be.
The key takeaway: Daylight saving time disrupts our biology, but strategic light exposure and exercise can mitigate its effects. By prioritizing these habits, we can protect our sleep, well-being, and long-term health.
