If you’re running the Los Angeles Marathon this Sunday, this will not be a typical race day.
The forecast is calling for temperatures around 84°, and runners will also lose an hour of sleep due to daylight saving time.
That combination changes how your body performs more than most runners realize. It is also why many well-trained athletes struggle late in hot marathons.
Why Heat Changes Everything
When temperatures rise, your body diverts blood to the skin to cool itself. This increases heart rate even when pace stays the same, a phenomenon known as cardiac drift.
The result:
- Higher effort at the same pace
- Faster dehydration
- Earlier fatigue
- Increased risk of cramping and GI distress
Many runners do not feel the consequences until miles 16–20, but the mistake usually happens in the first few miles.
The Hidden Factor: Spring Forward
Daylight saving time means losing an hour of sleep the night before the race.
Less sleep can:
- Raise resting heart rate
- Increase perceived effort
- Reduce early-race decision making
Combined with heat, fatigue arrives sooner than expected.
Smart Adjustments for a Hot Marathon
If race day is significantly warmer than your training conditions, consider:
✅ Slowing early pace expectations
✅ Using heart rate caps instead of strict pace targets
✅ Starting hydration earlier than usual
✅ Increasing sodium intake appropriately
✅ Using cooling strategies such as water, shade, or ice when available
Heat rewards patience and punishes aggression.
Why Many Runners Struggle at Mile 18
Late-race blowups are rarely about fitness.
They usually come from small early decisions:
- Starting too fast
- Underestimating hydration needs
- Ignoring rising heart rate
By the time symptoms appear, physiology has already shifted.
Need Help Adjusting Your Plan?
I’ve opened a limited number of 30-minute LA Marathon race strategy consultations through Saturday to help runners adjust pacing, hydration, and heat strategy intelligently.
If you’re racing, or know someone who is, you can learn more here:
https://app.paperbell.com/checkout/packages/204692
Run smart. Not stubborn.
-Martise