Why Suffering in the Summer Pays Off in the Fall
Heading into the summer every runner’s first thought is “how do I avoid the heat as much as possible”. While in many parts of the world it’s almost impossible to stay cool out there whether you choose the morning or evening, it’s worth noting that there is light at the end of the tunnel.
Yes, you need to endure the slower paces, higher heart rates, and wiping sweat in places you didn’t know had glands, but come the fall (when many runner’s “A” races are) you will be enjoying the fruits of your heat-labor. Train in the heat, to breakthrough in the cooler weather.
Why
If summer runs feel harder than they should, that’s because they are. When temps rise and humidity soars, your body has to work even harder to cool itself (sweat a lot more). This effect is exacerbated when humidity is combined with the head, something almost every runners in the eastern US states knows about. Essentially with humidity, your sweat cannot evaporate off of your skin (which causes the cooling effect), because there is already so much moisture in the air. So instead of cooling you, the pool of water over and slightly under your epidermis turns into a hot tub, making you sweat more.
Yet despite this somewhat non-ideal scenario, there is hope for a future training breakthrough. In these conditions, you are forcing your body to adapt to the heat & humidity. And thankfully, these adaptations tend to stick around, usually long enough for your big race fall race.
The main driver of this is more efficient thermoregulation and sweating. Being able to easily sweat a lot is a good thing, your body has adapted itself to regulate your body temperature more efficiently. More precisely, you start sweating earlier, before you become too overheated. While this may seem annoying or even bad from a training standpoint (in cool weather most runners readily avoid sweating) this becomes a great thing for fall racing, since in cooler weather overheating is not a problem. Your thermoregulation is now keeping you even throughout your race.
There is also a mental side of training in the heat. I avoid anything too “woo-woo”, but simply putting yourself through summer heat training makes racing in the fall all that easier. Hitting race pace for 15 miles in the heat at peak mileage makes racing the full 26 in weather 30 degrees F cooler that much easier. It’s similar to training at 8,000ft elevation and then coming down to sea level and racing. Speaking of which…
How (yeoman’s altitude?)
Is the heat & humidity the yeoman’s altitude? Not all of us have the ability to bed down in Flagstaff or Boulder for the summer, but fortunately enough you will probably experience a heat wave or two.
How this term came to be is two-fold:
Increased Plasma Volume:
When your body heats up from running (or any exercise), your body needs to cool itself by increasing your sweat rate and a multitude of other process’. To get these process’ done, your body has to increase your heart rate and this reduces the amount of blood available for your muscles and heart. To compensate, your body increases blood plasma volume (the liquid part of your blood) by retaining fluid (not peeing), hormone regulation (helps you hold on to water and sodium), and protein shifting which again helps with water retention. Essentially your body hoards water and makes the liquid part of your blood more abundant. More blood plasma = easier for your heart.
Simply doing this for 2-3 weeks can increase your blood plasma volume by 10-15%, compound this for 3-4 months of summer heat training and you will have yourself a new adaptation and eventual breakthrough.
In the short term, this helps with making you more efficient at cooling yourself, lower heart rate at rest & training, and improved heat resistance. If you were to also race in the heat, then you will be more well suited if you hadn’t been training in the heat.
In the long term, more blood plasma means more stroke volume (more on this soon), which means you get more oxygen to your muscles which means you can run faster at a lower cost. More red blood places are created, which is why people tend to say heat training mimics altitude training, which also increases oxygen delivery and aerobic performance. You will also begin to recover faster, as your body can clear waste quicker and deliver needed nutrients to damaged muscles.
TLDR: Training in heat —> Plasma expansion —> Cardiovascular efficiency —> Cooler weather performance boost
Increased Stroke Volume:
First off, stroke volume is the amount of blood your heart pumps out with each beat. The higher your stroke volume, the less your heart needs to beat (at rest). It’s part of the cardiac output equation where Cardiac Output = Stroke Volume x Heart Rate. The more blood your heart can pump per beat, the more oxygen gets delivered to your muscles. You should note that on prolonged efforts, stroke volume decreases for many athletes, meaning your heart rate has to increase to keep your cardiac output constant. This is known as HR drift.
Since we already know heat training increases blood plasma volume (see above), this now means that your body has more plasma readily available to pump through your body AKA you can have a higher stroke volume. This is great, especially at lower efforts such as zone 1-2 as you can hold a lower HR with the same cardiac output (cardiac output stays constant, stroke volume goes up, heart rate goes down).
More blood per beat = less beats!
But the real adaptations come not only from being able to deliver more blood, but your body adapting and learning how to use the higher stroke volume to it’s advantages. Being able to effectively use the higher stroke volume to run more efficiently is where the gains are made. Muscle recruitment, increasing mitochondrial density, slow-twitch fibers become more fatigue resistant, tendons become more stiff, expanded capillary network, and higher hemoglobin levels. This is just to name some of the higher level ones, but the body’s process’ to make you a more efficient runner are many.
TLDR:" Heat Training —> Expanded Plasma —> Stronger heart —> Increased stroke volume —> better running economy —> more aerobic power
Heat Tips
While I am telling you to actively train in the heat this summer, I am also telling you to avoid it as much as you can. If you can run in the morning at 75F versus 90F in the afternoon, the morning will still give you the needed adaptations while reducing the health risks heat can bring about. You may also have to decide between lower heat + high humidity versus high heat + lower humidity. For example, Texas has cooler mornings with 90%+ humidity. While their afternoons are much hotter, but lower humidity. It’s up to personal preference, but you will find out quickly which the lesser of two evils.
Quick list:
Run as light as possible. Find lightweight shirts (I like Patagonia cap cool T), wear a singlet, or run shirtless. I am not a woman so I can’t comment on what females should wear (tank top, sports bra(?) but you get the point.
Carry a handheld water bottle. This is especially true for longer efforts (call it over 60 or 90 minutes depending on fitness). Throw some carb/electrolyte mix in there as well.
Do not overhydrate. Hyponatremia is real. Drink to thirst and don’t flood your body with fluids.
Oversalt your meals & eat fruit! Save yourself some money on the LMNT packets and start adding salt to your food for added sodium, and fruit for potassium, calcium, and other nutrients.
Sip, don’t chug after a run. Your body can only handle .8-1L of water an hour. Sip your way back to being hydrated, add salt as needed.
Don’t cram water in before a run. Being overhydrated and having to pee during your run + sweat a lot will only lead to electrolyte imbalances.
Year-Round Heat Training?
Can you parlay this newfound fitness from summer heat training into an all year training regimen? Even when the weather cools down, you still want to stay on top of your heat adaptations, namely stroke volume and hemoglobin levels.
An easy win is to train normally, then get in a hot bath or sauna immediately after your run to keep your core temperatures hot, and sweat level high. If you don’t have access to a sauna, a hot bath will work fine. All we are looking to do is trigger a heat response from your body. Since your core will already be warm from your run (even in cooler weather) hopping in the tub/sauna will give you that easy boost. Start with 10 minutes and work your way up to 30. This also can promote and start the recovery process, delaying muscle soreness and keeping your fresh.
Feel free to hydrate (with electrolytes) between the run and the heat exposure, even brining your fluids in the tub/sauna is fine too. Studies have shown that just 3 weeks of post-run heat exposure protocol have improved time-to-exhaustion in endurance athletes (by increasing plasma volume).
Indoor heat sessions. I don’t always recommend this, as it can hamper performance. I’d rather have an athlete do their prescribed workout of the day, then hop in the sauna. But one way to incorporate this is to complete your run, then hop on the indoor trainer/treadmill with a heat suit (layers of clothes if you want) on and get a solid 15-20min in at a zone-3 type medium intensity.
Passive heat acclimation also works well. If you have access to a sauna, using it for 30-40 minutes a day (not after you run or on days you don’t run) also helps you adapt to heated environments.
Whichever heat exposure option you choose, the premise is the same. Increase your body temperature to increase your blood plasma volume, and enjoy the benefits. PS doing this all winter will help you come summer time each year.
Enjoy your summer!
-BTR
Fuel with IntraChew Gummy Bears
I discovered your substack yesterday and loved your approach to running. Do you have any books, courses or references to help me learn more about running as a coach? Thanks a lot!