A Study Of 316K Runners Found This Surprising Link To Cardiac Arrest
You can follow your marathon training plan to a T and still have one unpredictable variable to contend with: the weather.
A cool day can turn warm, or a mild forecast can give way to a sudden temperature drop. Now, a recent study1 suggests those temperature swings in the days before a race may matter to your heart, too.
About the study
Researchers looked at whether changes in temperature before a marathon were associated with sudden cardiac arrest during the race.
They used "apparent temperature," which is basically how hot or cold the weather feels to your body rather than just the number shown on a thermometer. It takes things like humidity and wind into account, since a 60-degree day can feel very different depending on the conditions.
The team analyzed 12 years of data from the Taipei Marathon in Taiwan, including more than 316,000 people who ran the full or half marathon.
They compared temperature changes during the week before each race with the number of sudden cardiac arrests during the event.
Bigger temperature swings were linked to more cardiac arrests
Larger day-to-day changes in apparent temperature were associated with a higher rate of sudden cardiac arrest during the race. Each step up in temperature variability was linked to a rate of cardiac arrest more than six times higher.
But there's important context.
There were only 13 cardiac arrests among more than 316,000 runners, so these events were extremely rare. The study also can't show that temperature swings caused the cardiac arrests.
Most cases occurred during the final quarter of the race, when runners had already been exercising for an extended period. Men also experienced cardiac arrest at a higher rate than women.
RELATED READ: Is This The Best Supplement For Energy?
Why changing temperatures could matter
Your body is constantly adjusting to its surroundings.
When temperatures shift, your heart, blood vessels, and other systems help keep your body temperature stable. Those changes can affect things like heart rate and blood pressure.
During a marathon, your cardiovascular system is already working hard to deliver oxygen to your muscles.
The researchers suggest that repeatedly adapting to changing temperatures could add to that strain.
Still, this is an early finding. The study was observational, meaning it identified a relationship but couldn't establish cause and effect. And with only 13 cases, the results need to be confirmed in larger studies.
What to keep in mind before race day
You don't need to panic every time the forecast changes. Instead, look at the bigger weather picture and pay attention to how your body responds.
- Check the week's forecast: Don't just look at race-day conditions. Notice whether temperatures have been relatively stable or changing significantly.
- Adjust when needed: If conditions have been unpredictable, don't feel locked into a predetermined pace. Stay hydrated and give yourself enough time to warm up.
- Take symptoms seriously: Chest pain, dizziness, or unexpected shortness of breath during intense exercise aren't symptoms to push through. Stop and seek medical attention if they occur.
The takeaway
Your race-day checklist probably already has shoes, fuel, and a weather check on it.
This research suggests there may be value in looking a little further back, too, although we need more evidence before temperature swings can be considered a true cardiac risk factor.
For now, think of the forecast as useful information, not a reason to stress, and let how you feel guide your effort on race day.
