Integrating interval training into your UTMB® training plan is essential for a thorough preparation ahead of the alpine challenge.
Why interval training is essential for UTMB® preparation
In trail running training, interval sessions build VO2 max and uphill power while conditioning the body to alternate between high-intensity efforts and recovery—a fundamental demand of mountain ultras.
Regarding frequency, the rule is simple: one session per week is enough for most of your training cycle, ensuring at least two to three recovery days between demanding workouts. High-intensity work peaks mid-training, then tapers down as race day approaches to make room for mileage volume and long runs. In the final weeks, intervals should only be done occasionally and at reduced intensity.
3 interval workouts to integrate into your training
There is no single interval format for the UTMB®: depending on your goal—explosiveness, uphill endurance, or aerobic capacity—the ideal session varies. Here are the three most effective workouts to rotate.
Session 1: short hill repeats
The goal is to repeat short hill reps on a climb that takes around one minute to run, on a steady and fairly steep gradient—ideally between 10% and 15%. Between reps, jog easily for about one minute on flat ground to bring your heart rate down.
Start with 8 to 10 reps and build up gradually to 15 to 20 over the weeks, based on how you feel.
A word of caution on descents: running fast downhill forces your quads to work eccentrically—vital for handling the long UTMB® descents, but the most traumatic movement in running and a frequent cause of injury. Descend under control first, build speed gradually over several weeks, and never aim for max speed in your early sessions. If you are prone to knee pain or persistent soreness, scale back and replace fast descents with a moderate pace.
Session 2: long uphill intervals
Here, the focus shifts from explosive power to sustaining a solid effort over time, just like on the long climbs of the UTMB®. Choose a 3 to 5-minute climb and run it at a sustained but sub-maximal pace, then jog back down easily to recover. Repeat the climb 4 to 6 times depending on your fitness.
This is the most specific of the three sessions for a mountain ultra, and the one with the lowest injury risk.
Session 3: 30/30 intervals to build VO2 max
On flat or gently rolling terrain, alternate 30 seconds of effort close to your VO2 max with 30 seconds of active recovery (jogging or walking). Complete a set of 10 to 15 reps. This format is especially valuable early in your training cycle or alongside hill sessions to maintain pure speed.
How to structure your interval session
Whatever session you choose, complete a 20-minute warm-up with an easy jog on flat terrain before starting the intervals. Finish the session with a 10-minute easy jog to relax your muscles and promote recovery.
Do not skip the warm-up or cool-down: most injuries happen on cold muscles or after stopping abruptly.
Frequently asked questions
What is the best interval training for trail running?
There is no one-size-fits-all workout. 30/30 intervals develop VO2 max, short hills build explosive power and eccentric endurance, and long intervals build uphill stamina. For the UTMB®, the best approach is to rotate these three formats rather than relying on just one.
How often should you do interval training before the UTMB®?
One session per week throughout most of your training, with two to three recovery days around it. Contrary to popular belief, do not ramp up intensity close to race day: the final weeks prioritise volume, followed by tapering.
Should you sprint downhill on short hill reps?
No, not straight away. Eccentric downhill work is beneficial, but it is the most taxing movement in running. Build your speed progressively over several weeks, and avoid fast descents if you experience knee pain.
Find out more
- Hill training with elevation gain
- Long runs to prepare for the UTMB®
- Improving downhill trail running
- Altitude training to prepare for the UTMB®
Photo credits: Clément Dumas.
