5 Common Marathon Training Mistakes (And How To Avoid Them)

Training for a marathon is one of the most rewarding challenges a runner can take on. Whether you’re preparing for your first marathon or chasing a new personal best, the difference between a great race day and a disappointing one often comes down to avoiding a handful of common mistakes.

At CMF Running, we’ve coached runners through everything from first-time marathons to major personal bests, and we tend to see the same mistakes appear again and again.

Here are five common marathon training mistakes and what you can do instead.

1. Choosing a Goal Time Based on Ego

One of the biggest mistakes runners make is choosing a marathon goal based on what sounds good rather than what their current fitness supports.

A common example is running a strong half marathon and immediately deciding that a certain marathon time should be achievable. The reality is that marathon pace and half marathon pace are very different. The marathon demands a different level of endurance, durability, pacing, fueling, and training consistency.

While ambitious goals are important, they need to be grounded in your current fitness and experience level.

A runner who races within their ability will almost always have a better experience than a runner who chases an unrealistic pace and spends the final 15 kilometres hanging on for dear life.

Ask Yourself:

• Why is this goal important?
• Is it based on my current fitness?
• Am I chasing a result or a great marathon experience?

The best marathon performances are often built on patience rather than ego.

2. Focusing Too Much on Weekly Kilometres

Many runners become obsessed with weekly mileage totals.

They compare their training to friends, Strava followers, or elite runners and assume that more kilometres automatically means a better marathon result.

It doesn’t.

Marathon training is about applying the right stress at the right time.

Running 80–100km per week six months before race day doesn’t necessarily make you better prepared than someone running 50–60km per week consistently.

In fact, building too quickly often leads to fatigue, burnout, or injury.

Instead of focusing purely on kilometres, consider:

• Time spent running
• Consistency over months
• Recovery between sessions
• Overall training quality

The goal isn’t to win training. The goal is to arrive at the start line healthy and ready to perform.

3. Not Knowing Your Training Zones

Many runners train without knowing their threshold pace, marathon pace, or aerobic training zones.

As a result, they spend too much time running in what coaches often call the “grey zone”—too hard to recover from properly but not hard enough to create meaningful adaptations.

Understanding your training zones allows you to:

• Run easy runs easy
• Execute workouts correctly
• Pace marathon-specific sessions effectively
• Avoid unnecessary fatigue

A simple threshold test can provide valuable insight into your current fitness and help guide your training.

When you know your numbers, your training becomes far more purposeful.

4. Doing Too Much Too Early

Excitement is often the enemy of good marathon preparation.

A runner signs up for a marathon and immediately starts doing:

• Longer long runs
• More workouts
• More weekly kilometres
• More intensity

The problem is that marathon training is a long game.

The most important marathon-specific training usually occurs in the final 8–12 weeks before race day.

If you’re already training at maximum capacity months before the race, where do you go from there?

A successful marathon build should progress gradually, allowing fitness to build naturally while preserving motivation and reducing injury risk.

Patience is a powerful training tool.

5. Only Focusing on Running

Running is only one part of marathon success.

The runners who perform best on race day usually pay attention to the things happening outside their running sessions.

These include:

Strength Training

Strength training improves durability, running economy, and fatigue resistance.

Even one or two sessions per week can make a significant difference over 42.2 kilometres.

Nutrition and Fueling

Your race-day nutrition strategy should be practised during training.

Learning how to consume carbohydrates while running is a skill that needs to be developed over time.

Recovery

Sleep, stress management, hydration, and recovery habits all influence how well your body adapts to training.

Injury Prevention

Addressing small niggles early through strength work, mobility, or physiotherapy can prevent bigger problems later in the build.

Final Thoughts

Marathon training doesn’t need to be complicated.

In many cases, success comes down to avoiding a few common mistakes:

• Set realistic goals.
• Focus on consistency rather than mileage.
• Understand your training zones.
• Build gradually.
• Prioritise the things outside of running.
• If you can do those five things well, you’ll give yourself the best chance of arriving at the start line healthy, confident, and ready to perform.

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