How Much Running Is Too Much?

Most runners understand that increasing training too quickly can lead to injury, but until recently, it wasn’t entirely clear which training patterns carried the greatest risk. A large study involving more than 5,200 runners has provided valuable insights into this question and may change how runners think about progressing their training.

Running places repeated stress on muscles, tendons, bones, and joints. While the body adapts remarkably well to training, the process of building tolerance to increasing demands takes time.

Problems can occur when the training load exceeds what the body is currently prepared to handle. This can contribute to common overuse injuries such as:

• Achilles tendinopathy
• Patellofemoral pain (runner’s knee)
• Shin splints
• Plantar heel pain
• Stress reactions and stress fractures
• Hip and gluteal tendon pain

Understanding how to progress training safely is therefore one of the most important factors in injury prevention.

Researchers followed 5,205 adult runners over an 18-month period, analysing data collected from Garmin running devices. During the study, participants completed more than 588,000 running sessions, making this one of the largest running injury studies ever conducted.

The researchers wanted to determine whether sudden increases in running volume, sometimes called “spikes” in training load, increased the risk of developing a running-related overuse injury.

The most important finding was surprisingly simple:

The study found that injury risk increased significantly when a runner completed a session that was more than 10% longer than their longest run from the previous 30 days. 

Compared with runners who kept increases within 10%, the injury risk increased when runners performed:

• Small spikes (>10% to 30% increase)
• Moderate spikes (>30% to 100% increase)
• Large spikes (>100% increase)

In fact, runners who more than doubled the distance of their previous longest run had the highest injury rates observed in the study.

Many runners use weekly mileage targets and popular workload measures such as the Acute:Chronic Workload Ratio (ACWR) to guide training progression.

Interestingly, this study found that weekly workload calculations were not useful predictors of injury risk. The researchers found no meaningful relationship between week-to-week mileage changes and injury rates.

Instead, the strongest predictor was the distance of an individual running session relative to the runner’s recent training history.

The findings suggest that many injuries may occur not because of a gradual increase in weekly mileage but because of an isolated “hero run.”

Examples include:

• Deciding to join friends for a much longer run than usual
• Suddenly adding a long weekend run
• Returning too aggressively after illness or injury
• Completing a race distance that well exceeds recent training

While these sessions may feel manageable at the time, the body’s tissues may not be adequately prepared for the sudden increase in load.

One of the key messages from this research is that consistent training appears safer than sporadic large increases in distance.

Building distance progressively allows muscles, tendons, bones, and joints to adapt to increasing demands over time. This gradual adaptation helps reduce the likelihood of overload injuries.

For most runners, success comes from accumulating weeks and months of consistent training rather than from occasional breakthrough sessions.

Even experienced runners can find it challenging to balance training progression and injury prevention.

At our clinic, we regularly work with runners of all levels, from beginners to competitive endurance athletes.

A running assessment can help identify factors that may increase injury risk, including:

• Training load errors
• Muscle strength deficits
• Running mechanics
• Mobility limitations
• Previous injury history
• Recovery and workload management

We can also help develop individualized running plans that allow you to safely increase volume while minimizing injury risk.

This large study reinforces an important lesson for runners: sudden increases in a single running session may be more important than weekly mileage changes when it comes to injury risk. Exceeding your recent longest run by more than 10% was associated with a significantly higher risk of developing an overuse injury. 

If you’re preparing for an event, returning from injury, or struggling with recurring running-related pain, physiotherapy can help you train more confidently and efficiently.

Book an appointment with our physiotherapy team today. We can assess your running-related concerns, identify potential injury risks, and develop a personalized plan to help you stay healthy, improve performance, and enjoy running for years to come.

Call us on 02 4981 3461
Visit us and book online anytime via our online booking platform: www.nelsonbayphysio.com.au
Find us at 210 Salamander Way, Salamander Bay NSW 2317 (opposite Tomaree Aquatic Centre)

Reference

Frandsen, J. S. B., Hulme, A., Parner, E. T., Møller, M., Lindman, I., Abrahamson, J., Simonsen, N. S., Jacobsen, J. S., Ramskov, D., Skejø, S., Malisoux, L., Bertelsen, M. L., & Nielsen, R. O. (2025). How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study. British Journal of Sports Medicine, 59(17), 1203-1210. https://doi.org/10.1136/bjsports-2024-109380