Why Do Runners Wear Foil Blankets After A Race?

We always see it at the end of a half marathon or marathon, when all of the runners come crossing the line and are almost immediately wrapped in a foil blanket whether they asked for it or not.

Why is that?

Foil blankets or wraps are given to runners after a cold-weather marathon to prevent hypothermia by reflecting heat back to the runner’s body as they are still dissipating heat from running for over 2 hours.

Nowadays it is also a big branding opportunity for the event sponsors, as it allows a big brand to be wrapped around everyone at the end of this large and probably high-profile event with lots of eyes on it. This is the plain and simple answer, but let’s dive into the details.

Why Do Runners Wear Foil Blankets?

What are Foil Blankets and What Do They Do?

The Foil blanket, otherwise known as HeatSheets are designed as really just medium-sized blankets made from foil used to trap heat in and prevent the body from freezing up and entering a hypothermic state. 

Keep the body temperature a stable level is the goal. 

They are used by mountaineers, first responders, and endurance athletes to ensure warmth will not merely just escape but also be trapped and reabsorbed by the body. 

Its construction is fairly simple, it’s made up of sheets of Mylar (a polyester film) that are then coated with aluminum. The reaction is quite simple as well because if the sheet is wrapped around your body, then the aluminum coating reflects heat back to your body so it can be reabsorbed by the body. 

Furthermore, they are pretty lightweight and relatively inexpensive to buy, which makes them a great bang for your buck relative to a down jacket or even a plain sweater. 

A foil blanket do not hold or retain moisture either, which makes them quite effective in wet or rainy environments. 

What Happens to The Body After a Race

A foil blanket are important for preventing any big mass emergencies at the end of a big race conducted in colder weather.

Even if it is cold, your body will be working overtime to generate large amounts of heat, which means your body’s natural cooling response is to sweat. This carries over into the end of a marathon where you will face a big drop off in heat generation, but still, experience the cooling response of sweating and the moist clothes that have absorbed your sweat during the race. 

The stark contrast between running something like marathon races, and then immediately stopping will leave the body confused and less able to respond to the environment. In most cases, marathon runners wear foil blankets after running whereas you don't see them as often with a 5K or 10K race. 

If a runner has been running for over 3 or 4 hours, then the body will be left with few resources to reach homeostasis on its own, which is a cold environment will lead to a hypothermic state very quickly. This can be a big cause for concern, especially in a mass group of people experiencing the same symptoms. 

Needless to say, things can get out of hand extremely quickly for emergency response groups if a large percentage of racers are in need of medical attention. 

Why Do Foil Blankets Help Runners After a Race

As we mentioned above, the foil blankets are an easy, affordable and convenient option to help massive amounts of runners quickly begin to reach homeostasis after competing in a hard effort, such as a marathon or half marathon. 

These foil blankets will trap all of the dissipating heat from these runners and redirect it back to them, which is a fairly genius and passive way to ensure they reach homeostasis again. 

It’s easy for compliance as well, runners are usually more than happy to dawn one of these foil blankets after a race, especially in the cold. 

This is essentially the perfect combination of factors that make foil blankets a prime option for runners after a long race like the marathon.

Do You Need a Foil Blanket?

As a casual road or trail runner, you probably don’t need a foil blanket on hand at all times, especially because these big city races provide them anyway. 

However, for the more dedicated athletes, it might be worth having a foil blanket around in case of emergency, especially because they are relatively inexpensive and have a long lifespan if well maintained. 

Some people might enjoy it in their car or personal first aid kit, as it is super handy to have around in low-stake emergency situations when someone is cold and exposed to the colder elements. 

The Bottom Line

So foil blankets are an effective and convenient way item to have around to keep dissipating heat from reaching a critical state. Now when you see all of these runners getting cloaked with one of these you will know why it’s foil and what it is actually doing for these runners. 

You may consider getting one just to have on hand for some more extreme cold situations, as they are convenient, affordable, and very packable. They could pretty much fit inside your pocket. So the space impact is low.

Feel free to do some of your own research to understand which might be the best foil blanket for you, but there is no need to get too fancy, as they provide the same basic benefits.