It’s Sunday, May 11, 2025, and I’m weaving through muddy trails, legs churning through 18km. My lungs are steady, my hydration vest feels like an old friend, and despite the fatigue from yesterday’s 22km run, I’m grinning. A month ago, 12km was a real effort. Now, 14km feels like a warm-up, my resting heart rate’s dropped like a stone, and running is starting to feel like home again. This is the magic of Zone 2 training, and it’s reshaping my body for the Ultra-Trail du Mont-Blanc (UTMB) in 2030.
After a decade away from trails, I’m back, grinding through Dubai’s heat and now London’s rolling paths. In this post, I’ll break down how four weeks of Zone 2 volume turned 14km into a breeze, why my resting heart rate is plummeting, and how you can use this approach to level up your own running. Whether you’re eyeing an ultra or just love the trails, here’s the real deal on building endurance.
The Power of Zone 2 Volume
Zone 2 is that sweet spot where you can chat without gasping. It’s the backbone of ultra-marathon training, building an aerobic engine that lets you go longer without burning out. Since April 14, I’ve been stacking 60-70km weeks, mostly at 130-136 bpm, inspired by legends like Hal Koerner and his Field Guide to Ultrarunning. The results? My body’s adapting fast.
Take my resting heart rate. On April 17, it was 65 bpm. By May 6, it was down to 55 bpm—a 15% drop, showing my heart’s getting more efficient. My pace is improving too: a 17km run on April 19 took 7:51 min/km at 131 bpm, but by May 11, I hit 7:00 min/km for 18km at 135 bpm. That’s aerobic progress, no extra effort needed. Science backs this up: Zone 2 boosts mitochondrial density and fat-burning capacity, per a 2023 Sports Medicine study. For UTMB’s 10,000m of climbing, this base is non-negotiable.
Want more on Zone 2? Check my post “Why I’m Running So Slowly: The Science and Struggle of Zone 2 Training” for the deep dive.
How I’m Seeing Progress
Four weeks ago, I was grinding out 12km runs in Dubai’s heat, feeling every step. Now, after consistent Zone 2 work, the game’s changed. My May 9 run - 12km at 7:29 min/km, RPE 2 - was a breeze compared to April’s 12km at 7:49 min/km, RPE 3. By May 10-11, I tackled back-to-back long runs (22km + 18km), hitting 40km over two days. My legs were tired, but my breathing stayed steady, and my form felt natural, like I was born to run.
My Training Stress Balance (TSB) tells the story. On May 11, it hit -21, deep in the “getting fit” zone (-10 to -30), as tracked by TrainingPeaks. This means I’m pushing hard enough to grow without overtraining. Moving from Dubai’s flat treadmills to London’s trails added ~500m weekly elevation, but Zone 2’s kept me steady. Runs up to 14km? They’re my new normal, barely a blip on the radar. I wrote about what I am tracking to influence training.
Tips to Make Zone 2 Work for You
Want to make 14km feel like a warm-up? Here’s how to start with Zone 2, based on what’s working for me:
- Find Your Zone 2: Use a heart rate monitor (aim for 60-70% of max HR) or the talk test—you should speak in full sentences. My Zone 2 started out at 115-134 bpm, but I’ve nudged it to 135-140 as my aerobic threshold climbs.
- Build Volume Gradually: Start with 3-4 runs/week, targeting 30-40km. I went from 51km to 70km over four weeks, adding 10-15% weekly. Don’t rush - slow growth prevents burnout.
- Track Metrics: Watch your resting HR (mine dropped from 65 to 55 bpm) and pace at consistent HR. Apps like Strava or TrainingPeaks make this easy.
- Be Patient: It took me four weeks to feel 14km as “easy.” Stick with it, and the gains will come.
No trails nearby? I made it work on Dubai’s flat roads and treadmills. Use what you’ve got - parks, hills, even stairs.
What’s Next for My UTMB Journey
I’m back in London, soon hitting Hampstead Heath and Richmond Park for ~500m elevation weekly. My next phase ramps up to 80km/week by June, with long runs stretching to 25-30km. I’m eyeing a trail half-marathon by December, targeting ~1:45, as a checkpoint for UTMB 2030. Every Zone 2 run is a brick in the foundation for those Alpine trails.
Want the full scoop on my five-year plan? Read my intro post for the UTMB 2030 roadmap. For more on endurance training, check iRunFar - they’re a goldmine for trail runners.
Keep Chasing the Trails
A month ago, 14km was a grind. Now, it’s my baseline, and running feels like slipping into a favorite pair of shoes. Zone 2’s not flashy, but it’s transforming my endurance, one steady step at a time. Whether you’re dreaming of ultras or just want to run farther, this approach can change your game.
What’s your Zone 2 experience? What distance feels “easy” for you now? Join me on Strava to share your journey. Here’s to dusty trails, steady hearts, and the mountains calling us forward.
Happy trails,
Kyle
