How Much Running Is Too Much New Study Flags High Risk Sessions for Runners
- scottrichardsonpt
- Aug 4
- 9 min read
Most running injuries do not arrive after one heroic workout. They usually follow a pattern: a runner feels good, adds a longer run, adds another, squeezes in extra mileage, then the shin, knee, Achilles or hip starts to complain.
A new cohort study, “How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study”, puts fresh attention on that exact problem. The study, led by Jesper Schuster Brandt Frandsen, Adam Hulme, Erik Thorlund Parner, Merete Møller, Ida Lindman, Josefin Abrahamson, Nina Sjørup Simonsen, Julie Sandell Jacobsen, Daniel Ramskov, Sebastian Skejø, Laurent Malisoux, Michael Lejbach Bertelsen and Rasmus Oestergaard Nielsen, looked at whether sudden increases in running distance were linked with running-related overuse injury.
The detail that matters is simple: the researchers explored whether a spike in distance during a single run, or across one week, compared with the preceding period, was associated with a higher risk of injury.
For coaches, personal trainers, recreational runners and serious amateurs, this is highly practical. The question is not only “how far can you run?” It is “how much more are you asking your body to handle than it has recently been prepared for?”
What the study actually looked at
The study title gives us several useful facts straight away.
It was a 5200-person cohort study, which means the researchers followed a large group of runners over time rather than only asking injured runners what they remembered doing. That matters because running injuries often build gradually, and memory can be unreliable once pain appears.
The study objective, as stated in the abstract, was:
“We explored whether a spike in running distance during a single session or over 1 week, compared with the preceding period, was associated with increased risk of running-related overuse injury.”
That sentence is worth unpacking.
The researchers were not simply asking whether running is dangerous. They were asking whether sudden increases in running distance raise risk. They also separated two common ways runners overload themselves:
One unusually long session
A bigger-than-normal week of total running
This distinction matters in real life.
A runner might do only three runs in a week, but one of them is much longer than usual. Another runner might keep every session sensible, but add extra runs and end up with a much higher weekly total. Both approaches can create a spike, but they stress the body in different ways.
The study also focused on running-related overuse injury. These are not usually freak accidents. They are the familiar problems that appear when tissues are stressed faster than they can adapt, such as tendon pain, bone stress reactions, patellofemoral pain, iliotibial band symptoms, plantar fascia irritation, calf strains and persistent shin soreness.
The central idea is clear: your injury risk may rise when your current run or current week is too large compared with what your body has recently been doing.
The real issue is not distance, it is the jump in distance
One runner’s “easy 10 km” is another runner’s injury trigger.
That is why fixed rules can mislead people. A 5 km run may be too much for a new client returning after years away from exercise. A 25 km long run may be routine for a marathoner. A professional distance runner may cover a weekly total that would break most recreational runners, yet for them it may be normal because they have built towards it over years.
This study’s framing is useful because it looks at distance relative to the preceding period. That is the coaching gold.
If a runner has recently been doing 3 km runs, a sudden 8 km run is a large spike. If another runner has been regularly doing 16 km long runs, an 18 km long run is a small change. The absolute distance is different, but the training stress must be judged against recent history.
This applies to weekly mileage too.
A jump from 10 km per week to 20 km per week may look modest on paper, but it is a 100% increase. A jump from 80 km to 90 km is larger in raw kilometres, but much smaller proportionally. The body feels both total stress and the rate of change.
This is why the phrase “too much running” is incomplete. The better question is:
Too much compared with what you have recently adapted to?
What this means for the average personal training client
For a personal training client running for general fitness, the practical message is not to fear running. It is to make running boring enough to repeat.
Most general fitness clients are not chasing a marathon personal best. They want better cardiovascular health, fat loss support, more energy, confidence, or a way to enjoy exercise outside the gym. For them, the biggest mistake is often enthusiasm without structure.
A common pattern looks like this:
Week one
Two short jogs, some walking, a gym session
Week two
A good run, no pain, growing confidence
Week three
A sudden long Sunday run because the runner feels ready
Week four
Shin pain, knee pain or calf tightness
The issue is not a lack of toughness. It is simply that connective tissues often adapt more slowly than the heart and lungs. The engine improves quickly. The chassis needs more time.
For general fitness clients, the best approach is usually:
Keep most runs easy enough to speak in short sentences
Build the habit before chasing distance
Add either distance, frequency or intensity, not all at once
Treat soreness that changes running style as a warning
Use walking intervals without embarrassment
A new runner might start with run-walk sessions, such as alternating one to three minutes of jogging with walking recovery. The goal is to finish feeling that another few minutes would have been possible.
Progress should feel almost too cautious in the early weeks. That is not wasted time. It is tendon, bone, muscle and joint preparation.
A simple personal training rule is this: do not let one run become the whole training plan. If the client’s weekly running has been low, the “big motivational run” should be resisted. A steady pattern beats a dramatic spike.
What this means for higher-level amateur runners
Higher-level amateur runners have a different problem. They are not usually reckless beginners. They are often consistent, motivated and knowledgeable enough to be dangerous to themselves.
They know that improvement requires overload. They also know their best performances came from periods of hard training. So when fitness starts to rise, they may add more distance, more workouts, longer long runs and races into the same block.
This is where the study’s focus on session spikes and weekly spikes becomes especially relevant.
A club runner training for a half marathon or marathon might think:
“I usually run 55 km per week, but I’ll push to 70 km this week because I’ve missed a few long runs.”
That may feel logical. But it creates a large change in stress. If that week also contains intervals, hills, a long run and poor sleep, the musculoskeletal load can exceed what the runner has recently handled.
For serious amateurs, the key is to separate fitness ambition from tissue readiness.
A smart progression might include:
One main long run change every few weeks
Recovery weeks that genuinely reduce load
Easy runs that stay easy
Strength work for calves, hips, hamstrings and trunk
Close attention to early tendon or bone pain
Fewer “make-up miles” after illness, travel or work stress
The biggest trap is cramming.
Missed sessions do not need to be repaid. Training is not a debt ledger. If you miss a week, your body does not benefit from squeezing those kilometres into the next seven days. That is exactly the kind of spike this research framework warns us to examine.
For amateur runners chasing improvement, the lesson is not to avoid hard training. It is to make hard training measurable, progressive and recoverable.
What this means for professional runners
Professional runners live in a different training world. Their weekly volumes, double-run days, recovery routines and medical support are far beyond what most people can copy.
Yet the same principle still applies: sudden unaccustomed spikes are risky.
For professionals, “too much” may not mean a distance that looks extreme to everyone else. It may mean an abrupt change after:
Returning from injury
Coming out of altitude training
Changing coach or programme
Adding track sessions after base training
Racing frequently
Travelling across time zones
Switching footwear or terrain
Increasing gym load alongside running load
At elite level, small changes matter because athletes already train close to their limits. A professional runner may tolerate high mileage when sleep, nutrition, surfaces, strength work and recovery are aligned. The same mileage can become risky during stress, illness or disrupted recovery.
For coaches working with elite or high-performance runners, the study reinforces a useful question:
Is this session hard because it is planned, or risky because it is a sudden jump from recent training?
The difference is huge.
A 30 km long run may be appropriate for a marathoner deep into a well-built block. It may be far less appropriate two weeks after a calf problem, even if the athlete’s aerobic fitness could manage it.
Professional running is not proof that big mileage is safe for everyone. It is proof that high loads require long-term preparation and constant monitoring.
Why the old 10% rule is useful but incomplete
Many runners have heard the advice not to increase weekly mileage by more than 10% at a time. It is a helpful guardrail, especially for beginners, but it is not a law of biology.
The new study’s focus suggests a more nuanced view. A weekly percentage only tells part of the story. The single-session spike may matter too.
For example:
Runner | Recent pattern | Risky change |
New runner | Three 3 km run-walk sessions | One sudden 8 km continuous run |
Fitness client | Two short treadmill runs weekly | Adding a long outdoor hill run |
Club runner | 50 km per week with 14 km long run | Jumping to 65 km with a 24 km long run |
Marathon runner | Consistent high mileage | Adding race-pace work inside an already longer week |
Professional | High planned volume | Returning too quickly after injury or travel |
A runner can follow a weekly mileage rule and still create a session spike. Equally, a runner can manage session distance but add too many extra runs in one week.
The more useful checklist is:
Is this run much longer than my recent longest run?
Is this week much bigger than my recent average week?
Am I adding intensity at the same time?
Have I slept and eaten well enough to absorb the load?
Is any pain changing how I move?
If the answer to several of these is yes, the session deserves caution.
How runners can apply this without overthinking
You do not need a lab, a coach or a complex spreadsheet to use the lesson.
Start by tracking three numbers:
Total weekly distance
Longest single run
Hard sessions per week
That gives enough information to spot most dangerous jumps.
For a general fitness runner, the aim may be to build from two manageable sessions to three consistent sessions. For a higher-level amateur, the aim may be to plan blocks where weekly volume and long-run distance rise gradually, with recovery built in. For a professional, the aim may be to scan for changes in load against fatigue, injury history and race demands.
Pain signals also matter. Normal training discomfort usually settles as you warm up or disappears after recovery. More concerning signs include:
Pain that gets worse as the run continues
Pain that changes your stride
Localised bone tenderness
Morning pain that is worse day by day
Symptoms that return every time you run
When those appear, reducing load early is usually better than pushing through until forced rest becomes the only option.
This article is for general information only and is not a medical diagnosis. Persistent or sharp pain should be assessed by a qualified health professional.
A practical way to define too much running
So, how much running is too much?
For most people, it is not a universal number. It is the point where the increase in stress is larger than the body’s recent preparation.
The study’s value is that it frames injury risk around real training behaviour: single runs and weekly distance compared with what came before. That is exactly how runners should think.
For the average personal training client, the priority is consistency. Build the habit, keep the early sessions comfortable and avoid the sudden “prove myself” run.
For the higher-level amateur, the priority is controlled progression. Improvement needs overload, but not random overload. Plan the bigger weeks, protect the easy days and stop trying to replace missed training with panic mileage.
For the professional, the priority is context. High mileage can be normal, but only when it fits the athlete’s current readiness, recovery and injury history.
The clearest takeaway is this: the risky run is often the one that looks reasonable in isolation but is a big jump from your recent training. Track your distance, respect the rate of change and let your body adapt before asking for more.
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