How to Increase Your Running Mileage Without Getting Injured

Whether you are training for your first 10K, preparing for a half marathon, or simply trying to become a more consistent runner, increasing your mileage is an important part of getting fitter.

But there is a point where more running becomes too much running.

One of the most common patterns I see in runners is a sudden increase in training load. You feel good, your fitness is improving, so you add an extra run, make your long run longer, or start incorporating speed sessions. Initially everything feels fine, until a niggle develops in your knee, Achilles, calf, shin or foot.

The good news is that increasing your running mileage does not have to mean increasing your injury risk.

The key is to give your body enough time to adapt to the demands you are placing on it.

Why does increasing running mileage cause injuries?

Running is repetitive. Every kilometre exposes your muscles, tendons, bones and joints to repeated impact and loading.

Your body is very good at adapting to this stress, provided the training load increases at a rate that your body can tolerate.

The problem occurs when the load increases faster than your tissues can adapt.

This doesn't necessarily mean that you have "weak" muscles or that there is something wrong with your running technique. Often, it is simply a case of doing more than your body is currently prepared for.

For example, if you have been running 15 km per week and suddenly increase to 30 km, you have doubled your running load. Even if you feel cardiovascularly capable of completing the distance, your muscles, tendons and bones may not yet be conditioned to tolerate it.

This is particularly important when returning to running after an injury or a period of reduced activity.

How quickly should you increase your running mileage?

You may have heard of the 10% rule, which suggests increasing your weekly running distance by no more than 10% each week.

It can be a useful starting point, but it shouldn't be treated as a strict rule that applies to every runner.

For example, someone returning from injury may need to increase more slowly, while a well-conditioned runner may tolerate a larger increase. Your current training history, injury history, recovery, sleep, strength and other activities all influence how much running you can handle.

Current NHS return-to-running guidance similarly recommends gradual progression and advises against increasing both distance and intensity at the same time.

A better question than:

How much can I increase my mileage this week?

is:

How much training can I increase while still recovering well?

A simple example

If you currently run around 20 km per week, your progression might look something like:

• Week 1: 20 km
• Week 2: 22 km
• Week 3: 24 km
• Week 4: 20–22 km
• Week 5: 25 km
• Week 6: 27 km

You don't necessarily need to increase every single week. Holding your mileage steady or having a slightly easier week can give your body an opportunity to absorb the training.

And remember: your weekly mileage isn't the only measure of training load.

Adding hills, intervals, tempo running, longer runs or significantly faster paces can all increase the stress placed on your body – even if your total weekly distance stays the same.

Don't increase everything at once

One of the most common mistakes I see is changing several variables simultaneously.

For example:

I'm going to run 5 days a week, increase my mileage, add intervals and start doing hill repeats.

That's a lot of new stress at once.

Instead, try to change one major training variable at a time.

You might first increase your weekly distance while keeping most runs easy. Once your body has adapted to that volume, you can gradually introduce more intensity.

Recent running guidance has similarly highlighted the importance of establishing a consistent aerobic base before introducing significant speedwork.

How do you know if you're running too much?

Not every ache means you need to stop running.

Some muscle soreness after a new training stimulus is completely normal. What matters is how your symptoms behave during and after your run.

A useful way to monitor your response is:

Green light - continue

You may be able to continue progressing if:

• You have mild muscle soreness after a run
• Any mild stiffness settles as you warm up
• Symptoms return to your normal baseline within around 24 hours
• Your running feels comfortable and your symptoms aren't progressively worsening

Amber light - modify

Consider reducing your training if:

• Pain is lasting more than 24–48 hours
• Symptoms are gradually becoming more noticeable with each run
• Your pain is changing the way you run
• You are feeling increasingly fatigued
• Your usual runs are starting to feel much harder
• You are struggling to recover between sessions

Berkshire Healthcare's 2026 return-to-running guidance similarly identifies pain lasting beyond 48 hours, worsening pain during a run, persistent swelling and sharp pain as reasons to reduce training.

Red light - stop and get assessed

You should stop running and seek professional assessment if you develop:

• Sudden or severe pain
• Significant swelling
• Loss of strength or function
• A feeling of instability or giving way
• Pain that is progressively worsening