Running Slowly is Hard on the Knees!

As I’m writing this in the air somewhere over the Irish Sea traveling back to London, tens of thousands of runners will be waking up in nervous anticipation of today’s London marathon.

Whether it’s your first or fiftieth marathon, whether looking to compete at the sharp end of the race, or just to complete the 26.2 miles, the training is hopefully now in the bank. Today is all about executing the plan, well rehearsed in your head, for real this time.

What about those who, through injury don’t make the start line?

This year, as every year, many runners won’t even make it to the start line, having frustratingly broken-down with injury during training.

Marathon training is tough-going. That’s for sure. Depending on what research you choose to cite, per year the injury incidence rate in runners can be as high as 74%.

Running is attritional on the body at the best of times. Add to the equation the weekly long runs increasing in duration over the last few months, and the increased weekly volume that comes with a marathon training plan, not to mention speed work, hill sessions etc… and it’s easy imagine how training load quickly mounts up.

I’m not just talking about more serious runners increasing their weekly volume to 60-100 miles. What follows is if anything more pertinent to the runners increasing (for example) from a comfortable ~25 miles per week to 35-40 miles per week during their marathon training block.

Clearly, increased mileage and therefore training load takes it’s toll on the body and is a risk factor to sustaining overuse running injuries in general… But what about the type of miles you’re running?

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Running Slowly is Hard!

The staple of any marathon training plan is the weekly long run, methodically increasing in distance over the duration of the plan, until your taper begins.

We’ve written before from a physiological point of view about getting the pace of the long run correct, something many people struggle with. Keeping this run comfortably aerobic helps build that endurance engine all marathon runners need.

All too often the message many runners need to hear is to slow down for these runs, to better develop their aerobic system. I’ve definitely been guilty of pacing my long runs too fast in the past. Turning an ‘easy 16 miles’ into a long tempo session it’s taken all week to recover from.


The old coaching adage definitely applies: Make your easy sessions EASY and your hard sessions HARD!

Focusing on the ‘Easy’ part of this sentiment, it’s important for us to consider the biomechanical effects of running slowly rather than just the physiological.

Earlier this year Danish researchers Petersen published a study where they had compared cumulative loads at the knee joint during slow-speed running and faster running.

The authors concluded that:

Slow-speed running decreases knee joint loads per stride and increases the cumulative load at the knee joint for a given running distance compared to faster running. The primary reason for the increase in cumulative load at slower speeds is an increase in number of strides needed to cover the same distance.

Simply put, when running slowly although each individual step is less stressful on the knee than running faster, the total stress on the knee is more per mile at slow speeds. Mainly due to the increased number of strides taken to cover the distance at slower speeds.

Don’t confuse this with me talking about cadence here. I’m talking about steps per mile at different paces, rather than steps per minute!

When this paper arrived in my inbox, it stuck a chord with me both in terms of application for the athletes I work with, and also my own personal experience…

My Own Slow Running Frustration

I see myself as being fairly robust and injury resistant as a runner. Working with injured runners day-in-day-out makes me even more grateful for this!

The only time I’ve ever suffered with Patellofemoral Pain (Runner’s Knee) was after six weeks or so of taking a beginner’s running group out twice weekly. The relatively low volume of very slow running (I would have been better off walking) played havoc on my knees.

Anybody who has been in the position of running with friends much slower than themselves will appreciate the difficulty in maintaining good running form, at a pace slower than that which comes naturally.

This brings me to the main point(s) of the article:

Don’t get me wrong; whether you’re training for a marathon, half marathon, 10k, 5k race etc… you absolutely need to run the slower aerobic miles in training to ‘build the endurance engine’. That’s a given.

However it’s the execution of these aerobic miles that often seem to let people down and place undue stress on the body.

  1. I find that while many runners appreciate the need to slow down to get the aerobic benefit to their long slow runs, some slow down too much. I’d rather have an athlete running these miles in upper Zone 2 (using a heart rate monitor) than barely moving out of Zone 1. Pacing is a skill to master!
  2. As I’ve written about before, maintaining running form at slow paces is an important focus! Here’s a previous article with some pointers for this. In my experience, a significant number of the injured runners I meet during marathon training season demonstrate what I’d generally refer to as a ‘lazy gait’ pattern when they show me their long slow running pace during running analysis. Of course technically my term ‘lazy gait’ means nothing. Essentially what I’m referring to is a pattern where they’re so focused on remaining relaxed and plodding their way though the easy miles that posture and cadence (to name just a couple of elements) begin to suffer.

As a quantifiable variable, cadence is a great place to start. We know that from a knee loading point of view, increasing cadence at a given pace has a positive effect for many runners. Another way of looking at this is to work on maintaining cadence on a long run, rather than allowing the legs to slow as you tire.

Next time you’re on a long slow run count your strides for one minute towards the beginning of the run. The in the last third of the run, do the same again.

Is the figure the same, or has your cadence dropped? If so, you can work on gently making shorter-quicker strides for the same pace.

The overall message here is to make your long run slow… but not too slow! As you do so, maintain awareness of form, rather than falling into the ‘more relaxed is better’ trap.

Let me know how you get on 🙂

Runner’s Knee Rehab Resources >>
Free Resources [PDF]

Image via Julian Mason

Last updated on March 2nd, 2021.


  1. Good article, and I actually agree. I used to do my long runs by monitoring my HR that slowed my cadence and I experienced knee pain. My natural cadence is around 185 which makes my HR go into the steady band but I am comfortable with that as I now concentrate on your drills and exercises.

    This does shift the 9 min miling into 8 min miling but I feel the effort is moderate and after a 15 mile run I still feel quite refreshed, plus the faster pace forces me into running at a better and more efficient form, in turn reducing the ground contact time and vertical oscillation.

  2. Totally agree. For it me it’s the ITB. If it seems like it’s going to give me grief, I cut the distance short and leg it!

    Taking a week to recover from a long run struck a chord with me, I struggle to keep the pace down on long runs so as you say it is effectively a long tempo run.

  3. Something that rings true to me. As an older runner 65 and have been running for over 30 years. Naturally I am a lot slower now I find that the pace I run at now a lot tougher on the knees, while obviously being older itself brings dodgy joints the slower running adds to that.

  4. Interesting article, good read and food for thought.

    I follow a training schema based primarily on extensive intervals: core components are 10-15x200m, 8-10x 400, 4-6x 1000m, 3-4x2000m, al done at rather specific paces. Besides these there are long(er) runs, but they will always be broken into alternating parts (larger part zone 1, smaller part zone 2, quick zone 3) and most often concluded with 5-8x 100m.

    Most trainings are below treshold, though once a week a fartlek or race at or above should be included.

    The main rationale: long slow runs are bad for technique.
    Break them up in parts and there is less deterioration, especialy towards the end.

    The interval pacing allows for developing the right reactivity in the muscles, right amount of springiness.

  5. I agree , I too have experience the pain of running slowly , I have had two knee operations to clear our debris from cartilage that had cracked off the back of my patella and in returning to running from the operations I found running slowly was much more painful than running at my normal steady pace , I still find easy runs tough on my knees 2 years after the op. so I now swim or cycle on easy days.

  6. Why not simply do the long runs by time instead of by distance?

    So, say, do a 2h long slow run, regardless of the distance covered. Instead of doing a fixed distance, whose time will be tied to weather, physical and mental conditions (caloric expenditure and load on the body much more prone to variability and less controllable).

    1. I absolutely agree! The research mentioned in the post definitely adds weight to the idea of training for time rather than distance. I usually say that when marathon training the maximum long run should never exceed 3 hours. Three hours seems to work well as a rule of thumb for the point at where you end up doing more harm than good with a long training run… just from experience.