Building your aerobic base: Ashley Paulson’s training philosophy for ultrarunners

Training for a race that lasts two or three days doesn’t start with a big week. It starts months earlier, with a foundation most people never see on race day. iFIT Trainer Ashley Paulson has built that foundation for more than two decades of racing, including a Triple Crown season chasing the Tahoe 200, Bigfoot 200, and Moab 240 in a single year.

Here is how she structures training to build volume, know when to push, and build a base that holds up under real demand.

Building volume without breaking down

“You have to build consistency before you build crazy mileage,” Paulson says. “It’s not about one massive week. It’s about stacking weeks of work that your body can actually absorb.”

A study of 119 runners training for an ultramarathon found that sudden spikes in weekly training load were associated with higher odds of injury in the following week, and that runners training under 30 kilometers per week had higher odds of injury and illness than those training 30 to 60 kilometers per week. [1]

At the Tahoe 200, that base is exactly what her coach pointed to heading into the race. “Your engine fitness, low intensity, miles and miles, is just insanely good right now,” Coach Joe told her. “That’s the key in these 200s.” Paulson’s training philosophy treats that aerobic engine as the thing that gets built over months of consistent work, not something you can manufacture in a single big week before a race.

Why low intensity training still matters

Paulson is direct about a common misconception. “For ultrarunning, I feel like speed work still matters,” she says. “So often it’s like, ‘you don’t need speed, we just need long runs.’ That’s not true.”

Still, the bulk of her training happens at a low, sustainable intensity she describes as a pace where a conversation stays comfortable, often referred to as Zone 2. Speed sessions still have a place in Paulson’s training, but they sit alongside that low-intensity base rather than replacing it.

Knowing when to push and when to back off

Every endurance athlete eventually faces a moment where the body is sending a real signal, not just a hard day. Paulson pays close attention to her resting heart rate trends as one way to tell the difference. “If it’s elevated compared to my normal baseline, especially for a few days, I take that as a sign to look a little closer at recovery, sleep, fueling, hydration, and stress,” she says.

That tracks with guidance on overtraining: changes in resting heart rate are commonly listed among the physical signs that training load has outpaced recovery. [2]

At the Tahoe 200, that line between pushing through discomfort and a genuine red flag played out in real time. Around mile 140, a respiratory issue common on that course, sometimes called Tahoe Lung, had worsened to the point that a race official stopped to check whether Paulson could safely continue. Her crew pulled her aside, got her warm, and worked through whether she had enough left to keep going. She did, and continued the race, but the moment illustrates exactly the distinction she describes in training: discomfort that builds you is different from a signal that something is genuinely wrong.

“Sharp pain, worsening pain, or anything that changes your stride is not something I want to push through,” Paulson says. “The goal isn’t to win every training day. It’s to show up healthy and ready when it counts.”

Training for terrain you can’t replicate at home

Not every athlete has mountains outside their door, and Paulson builds around that constraint rather than treating it as a limitation. “I spend a lot of time on my treadmill building elevation,” she says. “It’s such a great way to rack up climbing when you can’t get outside on the terrain you need. I’ll work on sustained climbs and build that strength in my legs so they’re ready for those long mountain ascents.”

She’s also found creative ways to prepare for heat. “I’ve used heaters around my treadmill to help simulate hotter conditions while running,” she says. Heat adaptation takes planning, and she’s careful about how she approaches it, paying attention to how her body responds. A treadmill can’t replicate everything, technical descents and uneven footing still need to be practiced outdoors when possible, but it can prepare the body for the physical demands a route will require.

Building a base for your first long race

Paulson’s advice doesn’t change much whether someone is training for a first 10K or a first ultra. “Build your base slowly,” she says. “I know, I know, patience is not exactly the most exciting part of training. We want the big miles, the epic workouts, the finish line photos, and the stories about how tough we are. But your body needs time to adapt. You’re building more than fitness. You’re building durability.”

Her core guidance: be consistent before worrying about being fast, keep easy days genuinely easy, and don’t compare your early training to someone else’s years of work. “Whether you’re training for your first 10K or dreaming about 100 miles,” she says, “the secret is pretty simple: build patiently, stay consistent, and make sure you still love the person you’re becoming along the way.”

Frequently asked questions

How do I build training volume without getting injured?

One observational study of ultramarathon runners found that sudden spikes in weekly training load were associated with higher odds of injury in the following week. [1] Building gradually avoids those spikes.

What is Zone 2 training and why does it matter for endurance running?

Zone 2 refers to a low, sustainable training intensity, the kind of effort where you can hold a conversation. Paulson builds the bulk of her training around this intensity, using harder speed sessions alongside it rather than in place of it.

How do I know if I’m overtraining versus just having a hard training day?

Tracking resting heart rate trends can help. Changes in resting heart rate are commonly listed among the physical signs that training load has outpaced recovery. [2] Sharp or worsening pain, or anything that changes your stride, are signals worth paying attention to regardless of heart rate trends.

Can I train for a race with mountains or elevation if I don’t have access to that terrain?

A treadmill with incline capability can help build the strength needed for sustained climbing, even without access to real elevation. Technical terrain like descents and uneven footing still benefit from outdoor practice when it’s available.

What’s the most important advice for someone training for their first long distance race?

Build your base slowly and prioritize consistency over speed. The goal is building durability your body can sustain, not chasing big mileage weeks before you’re ready for them.

Explore more

• The Tahoe Endurance Running Series

• The Washington Endurance Running Series

• How Ultrarunners Fuel for Races Over 100 Miles: Ashley Paulson’s Nutrition Strategy

• How to Plan an Ultramarathon: Ashley Paulson’s Race Day Strategy

• Ashley’s Endurance Run Club

• 740 Miles, Four Races, One Season: Inside Ashley Paulson’s Impossible Year

• Rest Days and Muscle Recovery

• Sleep and Muscle Recovery

• VO2 Max Explained: What It Is, Why It Matters, and How to Improve It

References

1. National Library of Medicine. Does a greater training load increase the risk of injury and illness in ultramarathon runners?

2. American Council on Exercise. Too Much of a Good Thing

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