How Much Running Is Too Much? Understanding Running Load and Injury Risk.

Running is one of the most accessible forms of exercise, all you really need is a pair of shoes and some pavement. And for so many people across Cardiff, from Bute Park joggers to the running clubs you’ll see along Cardiff Bay, it can boost physical health, mental wellbeing, stress relief and confidence.

But in clinic, we see the other side of running too. The niggles that don’t settle. Injuries that “came out of nowhere”. 

So a question we hear a lot is: 

How much running is too much? 

And annoyingly, the honest answer is, it depends. But there are some clear patterns, and recent research gives us a much better idea of where runners get into trouble. 

Is there such a thing as too much running? 

Yes, but it’s not about a specific mileage number. One runner might comfortably handle 40-50 miles a week. Another might struggle at 15. What matters more than the number itself is how quickly your running load changes and how well your body is prepared to cope with it. 

Recent research in British Journal of Sports Medicine looked at thousands of runners and found something really important: 

“The biggest injury risk wasn’t weekly mileage – it was sudden spike in distance, particularly in a single run.  

When runners increased the length of their longest run too quickly compared to what they’d been doing recently, their risk of overuse injury jumped significantly. 

Simply, your body copes best with gradual change, it struggles with big, sudden, jumps, even if your weekly mileage doesn’t seem extreme. 

Why sudden changes matter more than distance. 

Running places repetitive load through the same tissues thousands of times per run, this includes

your bones, tendons, joints and muscles. 

These tissues do adapt, but they adapt slowly. 

When runners: 

• Increase distance too quickly 

• Add a long run without building up 

• Return from injury or time off too fast 

• Increase intensity and volume at the same time 

When you do this, the tissues don’t get enough time to adapt. That’s when we start seeing overuse injuries. 

In our clinics in Cardiff, this often shows up as: 

- Achilles or patella tendon pain 
- Shin pain or stress reactions 
- Hip and knee pain 
- Plantar heel pain 
- Persistent tightness that never quite settles 

The Long Run Trap

One of the biggest risk factors identified in research is a sudden jump in the longest run of the week. 

If your longest run over the last month has been 6-7km, jumping straight to 12-15km can overload tissues, even if your total weekly mileage doesn’t seem high. Your body tenders to tolerate small, steady increases far better than big jumps, even if those jumps feel manageable at the time. 

What this means for runners:

Rather than asking “How many miles should I be running?”, a better question is: “What have I prepared my body for?” 

Looking at what you’ve done consistently over the past few weeks gives a much clearer idea of what your body can currently handle, and how safely you can progress.