Managing Mechanical Stress: The Key to Injury-Free Running
We've been hammering this point home for a while now: it's neither your running shoes nor your running technique that can prevent running injuries, but rather the management of mechanical stress.
But what exactly is mechanical stress management? It's simply the gradual and controlled increase in your training load.
The 10% Rule: Effective or Obsolete?
Traditionally, runners follow the 10% rule: increase their training by no more than 10% from one week to the next. This simple rule seemed logical to avoid runner injuries.
However, studies tend to show that this approach doesn't really prevent injuries. I actually analyzed this topic in depth in my article: The 10% rule: myth or reality?
New study on injury prevention
A new study published in the summer of 2025 in the prestigious British Journal of Sports Medicine provides crucial data for all runners. This large-scale research followed 5,200 runners for 18 months and compared three different methods for measuring the increase in training load:
The three approaches tested
- Specific increase for each session : Is today's session longer than the longest session in the last 30 days?
- Acute vs. chronic ratio : is the load of the last 7 days higher than that of the previous 21 days?
- Increase week by week : is the load of the last 7 days greater than that of the previous 7 days?
Categories of training volume increase
The researchers then classified the increases into four categories:
- No increase
- Slight increase (10% to 30%)
- Average increase (30% to 100%)
- Large increase (100% and more)
The surprising results
Of the 5,200 participants, 35% sustained injuries during the 18 months of the study. Without going into all the statistical details, here is the major finding: only the measurement of the session-specific increase in activity predicted the risk of injury.
The risk of injury as your output increases
Here's how your injury risk changes as your session length increases compared to your longest outing in the last 30 days:
- Same length as a recent release : normal risk of injury
- 10% to 30% longer : increased risk of 64%
- 30% to 100% longer : increased risk of 52%
- 100% longer (double!) : increased risk of 128%
Why this discovery changes our approach to training
For several years, the trend has been to monitor weekly training load to prevent injuries. However, these results demonstrate that it is the load of a single outing that best predicts the risk of injury.
This discovery explains why so many runners get injured after an unusual effort, such as their first marathon or a long run after a break.
The new simple rule to apply now
The good news? You don't need complex calculations or sophisticated apps to protect your body. Here's the golden rule to remember:
Look at your longest outing in the last 30 days and don't increase more than 10% in your next session.
It's that simple! This one-on-one approach is not only more effective, but also easier to follow on a daily basis.
Run smart, run long
The key to staying healthy and improving your running isn't blindly following trends, but understanding how your body reacts to training stress. By applying this 10% rule per session rather than per week, you significantly reduce your risk of injury.
Learn to run without getting injured
Want to deepen your knowledge of injury prevention and optimize your training? Join us for the Corporate Challenge, a program where we'll support you in completing your first 5K or 10K with your colleagues! It's a great opportunity to improve while being guided by our team!
Key points :
- Mechanical stress management: It consists of a progressive and controlled increase in training load to prevent running injuries.
- Limit of the 10% rule: This rule, which recommends increasing training by a maximum of 10% per week, does not effectively prevent injuries according to recent studies.
- Injury Prevention Study: A 2025 study followed 5200 runners for 18 months, finding that only session-specific increases predicted injury risk.
- Risk of injury depending on the increase in output: The risk increases significantly if the session is 10% to 100% longer than the last outing, with an increase of up to 128% if the length doubles.
- Change of perspective on training: Now, the load of a single individual session is more predictive of injury risk than the weekly load.
FAQ
What new approach is recommended to prevent running injuries?
It is advisable to limit the increase in the duration of each session to 10% compared to the longest outing in the last 30 days, which is more effective than the weekly 10% rule.
How does injury risk change with increasing running session length?
The normal risk of injury is observed if the session is similar to the longest recent one, but it increases by 64% to 128% if the session is 10% to 100% longer or double the length of the last outing.
What are the key findings of a recent study on running injury prevention?
The study found that only an increase in the duration of a session compared to the longest recent outing predicted injury risk, with an increased risk of up to 128% if the session was twice as long.
Is the 10% rule still effective in preventing training injuries?
No, recent studies show that this rule does not provide effective injury prevention, as the specific increase in a session is the only factor predicting risk.
What is mechanical stress management in running?
Mechanical stress management involves a gradual and controlled increase in training load to reduce the risk of running injury.
Hello Daniel,
Thank you for this summary, very interesting for the progressive management of a training load.
Regarding the results, I have 2 questions:
* At the beginning of the results, a notion of length is mentioned: duration or distance? Is it at equivalent/comparable effort? Typically, a long outing of 2 hours for 15 km and the same duration for 20 km is a significant additional effort factor and yet of “the same temporal length”! Duration is mentioned later on these same statistics, but no longer length…
* Surprising figures for injury risks for 10-30% and 30-100%: we have 64% then "just" 52%. Teasingly, we could suggest going straight up to +30% which would be less risky than 10% (lol), which is not logical at first glance!
But this statistical increase is quite surprising and interesting in relation to an idea of weekly load.
But I may be misinterpreting the idea of this study: This would therefore indicate that we can increase the load one week without increasing the "normal" risk, as long as we do not exceed the longest outing done? Increasing a weekly load by 30% without increasing the long outing is a significant increase in mechanical stress and an increased risk of injuries.
Or should we not read the study rather as a comparison of equivalent sessions (or type of session)? e.g.: 3 training sessions / week: at random: 1 interval training, 1 specific training, 1 long run. The comparison here would be for each of the sessions with regard to similar sessions of the past weeks (interval training vs. past interval training, long run vs. past long runs, etc.). I would find this more logical and understandable. This would therefore imply reasonably limiting the load of a session to 10% compared to an equivalent session spent over 30 days (and not over 7 days as we regularly read everywhere in the written or electronic press), and this, for each of the sessions of the week.
Thank you for your articles, always a pleasure to read you!
Best regards,
Guillaume
Hello William,
Of course, the study must be taken in a broader context, because if we apply it literally, we could consider that we can increase our number of kilometers by 10% per day and be in the low injury risk group.
The study is retrospective and analyzes people's training. To obtain more interesting results, a prospective study would be required in which participants would be given certain rules and the effectiveness of these rules on injury risk could be assessed.
My takeaway is that you need to slowly increase the length of your long runs and probably do them fairly regularly. I'd be more inclined to rely on the number of km if you're running on the road, since the main factor is the number of impacts.
We're talking about duration (long outings), but is there any study or recommendation on the intensity of the sessions? For my part, my injuries are often related to high-intensity training. Thank you
The study does not venture into assessing injury risk versus intensity. That's more complex, though.
There are indeed several injuries that are more related to training intensity than volume.