Jim Walmsley is one of the most iconic endurance athletes of the modern era. Known for his historic wins at the JFK 50 and Western States 100, and now celebrated as the first American man to win UTMB, Walmsley has cemented his legacy in trail and ultra running history. In recent years, he’s continued to evolve — blending massive mileage with smart recovery and cross-training to stay at the top of his game. So what does it take to train like one of the best in the world? In this article, we’ll dive deep into Jim Walmsley’s brutal yet calculated training regime — and explore the one-percenters he’s added to stay ahead in the ultra world.
Jim follows the Lydiard approach to training, which involves high volumes of running at slower to medium pace. He is known for running up to 175 miles per week, but with big miles comes the risk of injuries and burnout. In recent years, Jim has started incorporating other forms of exercise that build strength and cardio endurance, while reducing the impact on his body.
Fast Long Runs
Walmsley posts all of his training on Strava. He is open with this mileage, splits and recovery. He holds very little back.
One of the most startlingly obvious things is how amazing his endurance is. It must be noted that most of his long runs are performed on trails, somewhat slower than road. Nonetheless, they are not slow. In the below long run Walmsley covered 50km over trails averaging 3:27 per km. Wow…
Huge Mileage
Walmsley is classic Lydiard. He covers approximately 175 miles per week (just over 280km). This is serious mileage for any marathoner, historically and present.
Long Repetition Sessions
A common session for an elite marathon runner is often 8 x 1km, 10 x 1km or 12 x 1km. But 20 x 1km, that is legit hardcore. Walmsley’s splits are impressive, without being earth shattering.
Speed his Achilles Heel
Walmsley has run 3:48 over 1500m, which is good, but not world class. Brett Robinson, one of Australia’s best marathoners, has a 1500m PB of 3:38 (and a marathon PB of 2:07:31). Whilst Bekele, has clocked 3:32 for 1500m. Speed will be Walmsley’s Achilles heel, he will need to find a lot of it, and quickly. Below is an example of a smallish 200m session he completed recently.
And Once Again, Amazing Endurance
Just…check…this….out, the last 23 splits of a 48mk long run (on trails).
The One Percenters
Some of the other fitness modalities that Jim has started incorporating into his training include:
- Long Bike Rides: Jim has been increasing the number of long bike rides on his recovery days. These rides can be 30-60 miles long, allowing him to improve his cardiovascular fitness without putting stress on his legs and joints.
- Cross Country Skiing: Jim has also started incorporating Nordic skiing into his training. It is a very tough sport that improves leg strength and cardio, and it is also low-impact, making it a great way to improve overall fitness for mountain running while taking pressure off his legs.
By training smarter and adapting with age, Jim is setting himself up to potentially sustain his level of performance for many more years to come. He is not keeping his training a secret, and the formula is simple. His base is built on running a lot of miles weekly, adding in a combination of speed work and intensity, and using other activities that help him recover and sustain his performance.
Examples of some of Walmsley’s key sessions:
3 Mile Warm Up
8 x 200 Meter Repeats
400 Meter Jog Recovery
2 Mile Cool Down
3 Mile Warm Up
12 x 400 Meter Repeats
100 Meter Recovery
2 Mile Cool Down
4 Mile Warm Up
5 x 1600 Meters Repeats
2 Minutes Rest Between Each Round
2 Mile Cool Down
3 Mile Warm Up
12 x 400 Meter Repeats
600 Meter Recovery Jog
2 Mile Cool Down
3 Mile Warm Up
10 x 800 Meters Repeats
260 Meter Recovery Jog Between Rounds
1 Mile Cool Down
3 Mile Warm Up
4 x 2 Mile Repeats
2 Minutes Rest Between Each Round
1 Mile Cool Down
3 Mile Warm Up
10 x 1 Mile Repeats
2 MInutes Rest Between Each Mile
3 Mile Cool Down
Hybrid Mode Engaged
In 2025, Jim has fully embraced the hybrid athlete identity. His training now regularly features structured doubles combining 20-25km trail runs in the morning with tempo rides or ski erg work in the evening. The days of hammering 280km per week are more selective, with smarter cycles that ramp intensity, then retreat into recovery. He’s reportedly working with a sports scientist in Europe to monitor biomarkers like HRV, lactate threshold, and cortisol levels — all to delay burnout and preserve performance deep into his 30s.
The Verdict
At 35, Walmsley evolved — blending science, maturity, and still a hell of a lot of mileage. He’s not slowing down. If anything, he’s just getting smarter — and possibly, even better.
