12 Week Trail Marathon Running Programme

Trail running offers many runners an extra degree of challenge over your traditional road 5k, 10k or marathon. With technical terrain, uphills and downhills, they require a different kind of training than what you’re likely to put in for a traditional road race.

This 12-week trail running programme will prepare you for the specific demands of trail running. The plan is perfect for both road runners transitioning to trails or those wanting to get after their first marathon distance run.

This programme is divided into three key blocks:

1. Foundation & Endurance (Weeks 1-4)
2. Strength & Speed (Weeks 5-8)
3. Race-Specific Preparation (Weeks 9-12)

Key Concept of the Programme

Race Pace: This refers to the pace at which you plan to run your race. In this programme, race pace is used in three main variations, which we will refer to to determine your level of effort:

• 1-hour race pace (90% effort): The pace you could sustain for a race lasting around one hour. This is close to a hard effort but not a sprint. You’ll be working hard, with your breathing rapid and speaking limited to just a few words at a time.
• 2-hour race pace (75-80% effort): A moderately hard pace that you could sustain for a race lasting two hours. This feels tough, but you can manage to speak in short sentences.
• 3-hour race pace (65-70% effort): A more comfortable, steady pace that you could sustain for around three hours. You should feel relaxed enough to hold a conversation, with just a slight increase in breathing.

Block 1: Foundation & Endurance (Weeks 1-4)

Objective: Build base endurance, get comfortable running on trails, and start introducing key workouts such as hill reps and fartlek sessions.

This phase is about gradually adapting your body to trail running by focusing on consistent mileage. You will start with shorter runs and build your endurance, focusing on developing a sustainable running pattern that you can continue to follow throughout the programme.

Weekly Structure

• Fartlek Workouts: These sessions introduce speedwork with a mix of fast and easy intervals. For example, you may do 4 x 4-minute fast efforts (at your 1-hour race pace) with 2 minutes of easy jogging in between.
• Easy Runs: These are your recovery runs, done at a conversational pace (30-40% effort). They help with recovery and maintaining your weekly mileage without taxing your body too much.
• Long Runs: Starting with 8 miles and gradually increasing, these runs will have 30-40% of the total elevation gain you’ll face on race day. Running on hilly terrain is essential to prepare your legs for climbs.
• Hill Reps: These sessions, such as running 4 x 2.5 minutes uphill, are designed to build strength and improve your ability to handle inclines. Run at a hard but sustainable pace, focusing on consistency across each rep.

Example Week

Day	Session
Monday	Rest
Tuesday	Fartlek: 4x4 minutes @ 1 hour race pace. 2 minutes easy between each effort
Wednesday	6 miles easy
Thursday	Rest or 5 miles easy
Friday	Tempo Run: 15 minutes @ 2 hour race pace
Saturday	Rest
Sunday	8 mile long run with 30% of target race’s total elevation gain

Block 2: Strength & Speed (Weeks 5-8)

Objective: Increase intensity through hill work, longer fartlek sessions, and progression runs, while continuing to extend your long run distance.

In this block, you’ll focus on adding harder sessions to build both speed and strength. This includes longer tempo runs and more intense hill sessions, whilst  gradually increasing your long runs to prepare for marathon distance.

Weekly Structure

• Tempo Runs: These sessions will increase in length and intensity. For example, a 20 minute tempo run at 2-hour race pace (75-80% effort) helps to improve your ability to run at a steady, moderately hard pace.
• Hill Fartlek: On undulating routes, run hard on the uphills and recover on the flats and downhills. This helps to adapt your body to handle varied terrain while still maintaining effort.
• Progression Runs: These runs will help you get comfortable pacing yourself and pushing harder towards the end of a run. For example, a 20 minute progression run could involve running the first 10 minutes at your 2-hour race pace, followed by the final 10 minutes at 1-hour race pace.
• Long Runs: These become longer and more specific to your race. You’ll build up to 17-mile long runs, with up to 65% of your target race’s total climb incorporated.

Example Week

Day	Session
Monday	Rest
Tuesday	Hill Fartlek Run: 20 minutes of hard on climbs, recovery on descents
Wednesday	6 miles easy
Thursday	Rest or 5 miles easy
Friday	Tempo Run: 2 x 12 minutes at 2 hour race pace with 3 minutes jog in between
Saturday	Rest or 5 miles easy
Sunday	15 mile long run with 50% of target race’s total elevation gain

Block 3: Race Specific Prep (Weeks 9-12)

Objective: Fine tune your race readiness with longer runs, higher intensity workouts, and practice race conditions like fuelling and pacing.

In this final training block, your workouts become more race specific, simulating race day. You’ll include longer tempo runs and progression sessions, alongside big long runs that mirror race day effort and elevation.

Weekly Structure

• Long Runs: These now reach 17-20 miles and include up to 75% of the total elevation you’ll encounter on your target race day. This is the time to practice your fuelling strategy, trying out gels, snacks, or electrolyte sachets & hydration drinks that work for you.
• Progression Runs: Longer progression runs, such as a 25 minute progression from 3-hour race pace to 1-hour race pace, help prepare your body for changing efforts during the race.
• Hill Reps & Tempo Workouts: Continue building strength and speed through hill reps and tempo runs. A 30 minute progression run, for example, starts easy and gets progressively harder, allowing you to simulate the final hard miles of a marathon.

Example Week

Day	Session
Monday	Rest
Tuesday	Tempo Run: 20 minutes at 1 hour race pace (hard effort)
Wednesday	7 miles easy
Thursday	Rest or 4 miles easy
Friday	Progression Run: 25 minutes (10 mins at 3 hour pace, 10 mins at 2 hour pace, 5 mins at 1 hour pace)
Saturday	Rest or 3 miles easy
Sunday	20 mile long run with 50% of target race’s total elevation gain

Key Sessions Explained

Fartlek Runs

A Fartlek is a form of speedwork that involves alternating periods of fast running with slower recovery efforts. For example, you might run hard for 4 minutes at 90% effort (1-hour race pace) and then recover for 2 minutes by jogging slowly. These sessions improve your ability to change pace quickly, a key skill for trail running where technical terrain often requires pace changes.

Tempo Runs

Tempo runs are performed at a steady but challenging pace, usually around 75-80% of your maximum effort (2-hour race pace). These help improve your stamina and ability to sustain a faster pace for extended periods, and get you used to running at a consistent pace. For example, a 20 minute tempo run at a 2-hour race pace is moderately tough but sustainable.

Hill Reps

Hill sessions are needed for trail race training. Running 4-6 minutes up a hill at a hard pace improves leg strength and your ability to handle elevation during your race. The key is to run consistently, maintaining a sustainable effort across each rep you perform.

Progression Runs

In progression runs, you start at an easier pace and gradually increase your speed. For instance, in a 30 minute progression run, you might begin at your 3-hour race pace (65-70% effort) and finish at 1-hour race pace (90% effort). These runs help teach you how to manage your pace and effort over a longer race distance.

Long Runs

These are the building blocks of marathon training. Long runs should gradually increase in distance and elevation gain to prepare your body for the demands of race day. For trail races, incorporating elevation gain into your long runs is needed.

Conclusion

This article has taken you through a 12 week training programme for your first trail run race or marathon. If you’re looking for some pieces to wear during your training or on race day, be sure to check out our 247 collection.