Unlocking My Fastest Year Yet

My last marathon year was 2021 and it was similar in many ways. I had the ötillö swimrun world championships in September as a major training focus, so the same as I will have this year. If I am going to beat my four year younger self what will I have to do differently?

I was faster going into 2021, coming off a December 17:32 5k and a January ½ Mara in 1:23:37 - advantage younger Tom. Still, I got an Achilles injury in early spring and couldn’t run-train until June. So a key factor will be staying injury-free through a combination of more gym strength work, hill sprints, and making better decisions on how hard to push!

I made the decision to do the Uppsala Marathon after ötillö which gave me only 8 weeks of focused preparation. This year I have 10 months! This means I can structure the training with more precision to ensure that performance marks can be met along the way.

High-carb fueling was in play then, as it will be this time. The low temperature was on my side in Uppsala and I hope it won’t be hot in Valencia. 

Talking about heat, one of the game-changers I’m adding to my training this year is heat adaptation. With easy access to saunas here in Sweden, this is a no-brainer. 

Training my body to handle high temperatures might seem counterintuitive for a race in December. Valencia isn’t exactly a scorching marathon, with average race-day temps around 10-15°C (50-59°F) - ideal for running fast. But heat adaptation isn’t just for survival in hot races.

The body adapts to extreme heat by expanding plasma volume and this:

• Triggers red blood cell production → More hemoglobin = better oxygen transport

• Improves stroke volume & cardiac output → Heart pumps more efficiently, reducing effort

• Enhances sweat response → Body dissipates heat more effectively

• Stabilizes core temperature → Delays overheating & reduces cardiovascular strain

• Reduces perceived exertion (RPE) → Work feels easier at the same pace

In other words, I’m making my body more efficient at managing internal temperature and oxygen delivery. Two things that directly translate to running faster, no matter the weather. Increasing plasma volume signals the body to increase red blood cells - natural EPO! Stacking adaptations is what effective training is all about, and being able to do that at an enhanced baseline compounds this stimulus.

There are several structured heat adaptation methods, each with different time frames and levels of complexity. The two main approaches are differentiated by being passive or active.

Passive heat exposure uses heat exposure without exercise. A typical protocol would be to sit in a sauna for 20-30 minutes at 80-100°C (176-212°F) or to use a hot tub at 38-42°C (100-108°F) for 30-40 minutes, post-training.

Then we have active heat training either through training in hot conditions or overdressing and performing low to moderate-intensity sessions (60-90 minutes). 

Most sources say that these methods should be done daily for 7–14 days for full adaptation, although I saw one study on elite cyclists where they found a 17.3% blood volume increase after only a 4-day sauna protocol (sauna after training). That’s pretty incredible. No doubt an evolutionary biological hack that has allowed humans to survive and thrive in very hot environments - adapt fast or die!

I can’t see myself taking the active exposure path, and I have easy access to a sauna, which means I can integrate passive heat exposure without compromising my key workouts, here’s the plan:

Phase 1: Long-Term Maintenance (Feb - Oct 2025) with occasional concentrated blocks.

• Initial block with sauna heat exposure on 4 to 6 concurrent days, then

• 1-2 sauna post-workout sessions per week (20-30 min)

• Hydration delay strategy—waiting 15-20 minutes before drinking fluids to boost plasma expansion

• Repeat focused four-day booster block when convenient and won’t interfere with training

This keeps my body familiar with heat stress throughout the year without causing unnecessary fatigue. My understanding is that if you do year-round heat training you can increase your baseline by around 15% - allowing you to train harder and recover quicker.

Phase 2: Intensive Heat Acclimation (Nov 17 - Dec 1, 2025)

• Daily or every-other-day sauna sessions (25-40 min)

• Post-training heat exposure while slightly dehydrated to maximize adaptation

• Gradual duration increase (starting at 20 min, building to 40 min max)

This final heat block will fully prime my body for peak endurance efficiency heading into Valencia.

Phase 3: Taper & Maintenance (Dec 2-6, 2025)

• 1-2 light sauna sessions (15-20 min) to maintain benefits without extra fatigue

• Full hydration focus—no need to delay fluids at this point

• Recovery priority to arrive fresh for race day

Calling out big goals is always scary, and to be honest with you I’m already doubting myself. But sometimes you just have to shoot your shot. My training plan is dialed in with Envol’s Start Line Ready. The mileage, the workouts, the nutrition—it’s all there. Will it work? I’ll find out in December. 

Valencia, I’m coming for that PR, so bring on the heat!