A pesky new running metric from Garmin.
Why?
Because it's probably useful, and Garmin forces you to get it only with a watch upgrade. Grrr. But here's why it's a good metric, and you can decide whether you want it...or not.
Resources & Links:
Source Written Article by the5krunner: “https://the5krunner.com/2025/05/20/garmin-running-tolerance-all-you-need-to-know/”
Main Channel: https://the5krunner.com
My other channels: https://linktr.ee/the5krunner
—Credits:Content in this episode was generated using AI tools (NotebookLM) based on original content from @the5krunner, and other sources as cited.
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
Welcome to the Deep Dive. We take information you're
curious about and really dig in to find those valuable insights.
That's the plan. Today we're tackling something I
think is, well, really relevant for a lot of you pushing for
better times, maybe like the folks following the 5K runner.
Absolutely. How do you train effectively?
(00:20):
You know, push hard, but withoutconstantly getting injured.
Right. It's the age-old question for
runners, and today we've got some interesting stuff to look
at. Yeah, what's on the menu?
We're looking at Garmin's running tolerance feature,
digging into the science behind impact load and running, and
we'll even touch on how others, like I Measure you, are
measuring this kind of thing. OK, cool.
(00:41):
So the mission is really to get clear on what this running
tolerance thing is, and maybe how you can actually use it to,
well, run smarter. Exactly making that data work
for you. All right, let's start with
Garmin's running tolerance. Then what's the basic idea?
Well, at its core, Garmin developed it to help runners
spot, you know, potentially risky training patterns.
Risky how? Like doing too much too soon?
(01:02):
Sort of, yeah. It's about managing that balance
between stressing your body enough to adapt and improve, but
not overdoing it to the point ofbreakdown.
Getting a better handle on the physical stress, basically.
OK, so it's trying to quantify that stress beyond just how many
mile you run, because we all know a hard tempo feels way
different than an easy recovery jog.
(01:23):
Precisely. And that's where their concept
of impact load comes in. They're trying to measure the
actual mechanical load, the force on your body.
Not just distance. Not just distance.
Think muscles, joints, tendons, the whole system.
The key takeaway isn't just the distance, but the stress.
A short, intense run effectivelycounts for more.
(01:44):
OK, that makes intuitive sense, but how does my watch figure
that out? It's not exactly a bio mechanics
lab on my wrist. No, not quite, but it's pretty
clever. Garmin uses your data weight,
obviously how hard you're running.
Pace, heart rate zones, that sort of thing.
Yeah, intensity metrics and alsorunning dynamics if you've got
the right gear, like a compatible heart rate strap.
So cadence, ground contact time.Exactly, and they even factor in
(02:06):
hills, uphill, downhill. All that gets fed into what they
described as sophisticated tech like a neural network to
estimate the ground reaction forces.
Wow, OK, neural network. So it's estimating the pounding
based on all these inputs. That's the idea, And from that
estimation they calculate what they call equivalent mileage.
Equivalent mileage? What does that mean in practise?
(02:27):
Well, their examples suggest like a tough five mile run with
significant hills might have an impact load equivalent to maybe
8 miles of flat easy running. 8 miles.
OK, that's a big difference. It is, and conversely, maybe an
easy 3 Miller comes out as only 2.5 impact miles.
They also really stressed that downhill running can massively
(02:49):
increase impact. How much?
Potentially up to three times harder than running flat at the
same pace, according to their info.
Three times, right? That definitely feels true
sometimes. So the takeaway is clear, the
type of run dramatically changesthe stress.
Exactly. Short and hard equals more
stress, and you can actually seethis right in Garmin Connect
after a run. Yeah, they provide a chart shows
(03:10):
the impact load throughout the run.
You can see where the spikes were.
Which is useful for understanding which parts were
most demanding. OK.
So that's impact load for a single run, but then there's
acute load and tolerance sounds like they work together.
They do think of acute impact load as the running stress
you've built up recently. It's a weighted sum of the
(03:30):
impact from your runs over the last few days.
Weighted, meaning recent runs count more.
Precisely the impact from yesterday's run contributes more
than the run from five days ago.It reflects that current strain,
how your body is coping right now.
So if impact load is the stress of one session.
Acute load is the running total of stress lately.
(03:51):
You got it Like the current balance on your stress account,
OK. And tolerance, is that like my
credit limit? That's a great analogy,
actually. Yeah.
Tolerance is your body's currentcapacity to handle that acute
load. It's personal based on your
running history. My history like long term.
Both recent and longer term patterns.
It adjusts weekly. If you've been training
(04:14):
consistently, your tolerance, your your credit limit goes up.
If you take time off or reduce volume, it goes down.
Right. So if my acute load, my current
stress balance gets close to or goes over my tolerance limit
alarm bells. It's a caution flag, definitely.
Garmin frames it as a signal to be mindful.
Not necessarily stop running immediately, but more like, hey,
(04:35):
pay attention, maybe ease back. Because consistently going over
that limit is where injury risk climbs.
That seems to be the implication, yes.
Pushing beyond your current capacity repeatedly is asking
for Trump. But wait, you need to push to
improve right? To increase that tolerance.
Absolutely, and the system reflects that.
Consistently training appropriately, challenging
yourself without overdoing it, should gradually increase your
(04:59):
tolerance over time. That's how you build fitness
safely according to this model. And decrease volume tolerance
drops. Makes sense.
Where do I see this on my watch?Usually there's a running
tolerance glance or widget and you can often see it within the
context of your training week summary screen.
Got it. This sounds genuinely useful for
a planet. How does this connect to the the
(05:22):
broader scientific picture of impact and running?
Yeah, great question. This ties in really well with
research like that study reducing impact loading in
runners. OK, what did that study look at?
Well, scientists know that higher vertical impact loading,
basically how hard your foot hits the ground and how quickly
that force travels up your leg, is linked to common running
injuries. Like stress fractures, shin
(05:43):
splints, runner's knee. Exactly.
Fractures, patellofemoral pain, plantar fasciitis.
So this study aimed to see if they could actually teach
runners with high impact forces to run softer.
Teach them how. Through gait retraining, they
measured how hard runners were landing using accelerometers on
their shins. Measuring tibial shock, that
jarring feeling. Precisely tibial shock.
(06:05):
They also measured the vertical impact peak, the Max force, and
crucially, the rate at which that force builds up the
loading. Great.
So how quickly the impact hits, not just the peak force itself?
That sounds like what I measure you looks at too, right?
With their sensors. Yes, exactly.
Similar concept I measure you uses their.
I am used to capture cumulative lower limb impacts and loading
(06:28):
rate is a key factor there too. So how did the retraining work
in the study? They had a control period first,
then the retraining phase where runners got real time feedback
on their tibial shock. Like a beep or a display telling
them if they were landing too hard.
Something like that, yeah. Visual or auditory cues?
Then they gradually faded that feedback out, hoping the runners
would internalise the changes. And did it work?
(06:51):
Did they learn to run softer? Yeah, the results were pretty
impressive. They found significant
reductions in tibial shock, thatvertical impact peak, and those
vertical loading rates. How significant?
Tibial shock dropped by around 32% on average and importantly,
these changes lasted. They checked again a year later
and the runners were still running with lower impact.
A year later? Wow that's sticky.
(07:14):
Did everything reduce? Interestingly, the peak vertical
force didn't change much, which might suggest they weren't
necessarily pushing off less hard, but maybe changing how
they landed to absorb the force more smoothly.
Better mechanics. Fascinating.
And does lower impact mean fewerinjuries?
Did they track that? This specific study focused on
the bio mechanics, but they highlighted the strong link
(07:36):
found in other research. They mentioned a randomised
controlled trial where gait retraining to reduce impact led
to significantly fewer injuries.I think it was something like
62% fewer. 62% OK, that's huge. So the science definitely backs
up the idea that managing impactis critical.
Absolutely, and the study also found correlations between the
(07:56):
tibial shock measured by the sensor and those loading rates,
which kind of suggests that whatwearable devices can measure
might be a decent proxy for these important biomechanical
forces. Which links back to what Garmin
is trying to estimate, and maybeeven to discussions you see on
sites like the 5K Runner about using tech data.
Exactly. It suggests that tracking
something related to impact, even if it's an estimate like
(08:18):
Garmin's or a direct measurementlike I measure use, is valuable.
So Speaking of I measure U, how does their approach compare or
contrast with Garmin's? You mentioned?
They also measure impact load. Right I Measure U uses their
wearable IMU sensors, usually worn on the shins, to directly
quantify the cumulative impacts.Their impact load metric is
(08:39):
essentially calculated from the number of steps multiplied by
the intensity of each impact. So more of a direct count of the
hits scaled by intensity. That's a good way to think about
it. It's a direct measure of the
accumulation of impacts during activity, whereas Garmin is
estimating the overall biomechanical load using a wider
range of inputs like pace, dynamics, elevation and user
(09:01):
profile data fed into their algorithm.
Different paths to a similar goal.
Yeah. Quantifying stress.
Pretty much. It's also interesting that I
measure you distinguishes their impact load from another metric
they have called bone stimulus. Bone stimulus?
How's that different? Impact load is more linear.
More steps or harder steps equals more load.
Bone stimulus tries to model theactual physiological response of
(09:22):
the bone to that loading, which isn't perfectly linear.
Bones respond differently to different patterns and types of
stress. OK, so even more nuanced in how
the body adapts. Exactly.
But the big picture is that bothGarmin, with its integrated
watch features potentially boosted by accessories like the
HRM Pro, and specialised tools like I Measure you are giving
(09:44):
runners ways to understand theseforces.
Which fits right into that goal of smarter training, the kind of
thing someone aiming for A5 KPB,like many following the 5K
runner, would be really interested in.
Totally. It's about having more
information to make better decisions, manage load, stay
consistent, and ultimately perform better.
Consistency is came right and managing impact helps you stay
(10:05):
consistent. Definitely.
OK, let's bring it all together.What are the key practical
takeaways for you, the listener,from all this?
Well, first, if you have a compatible Garmin device, start
actually using the running tolerance feature.
Don't just let it be another data screen.
Pay attention to it, yeah. See how the reported impact load
for different runs, hills, speedwork, easy runs matches how you
(10:26):
feel. Look at how your acute load
tracks against your tolerance over Wix.
Does it make sense with your fatigue levels?
Treated like another feedback signal from your body, but
quantified. Exactly.
But, and this is crucial, it doesn't replace listening to
your actual body. The data is a tool, not the
absolute. Truth precisely If you feel
(10:46):
pain, persistent niggles or excessive fatigue, don't ignore
that just because your watch says your acute load is
productive or within tolerance. Use the data alongside your
intuition and feelings. Point Trust your gut too.
Always. But the science is clear.
Managing impact load is important for staying healthy,
and staying healthy is fundamental if you want to train
(11:06):
consistently and improve, which is obviously a core goal for
performance focused runners. Right, so summing up, Garmin's
Running Tolerance is this tool trying to quantify running
stress using biomechanical principles.
Looking beyond just mileage, science backs up the importance
of managing impact, and other tools like I Measure You offer
(11:26):
different, maybe more direct, ways to measure similar things.
That's a great summary. It all points towards more
informed training. So the final thought to leave
you with how might actively tracking and understanding your
own impact load, maybe using garments features, maybe
exploring other tools like I measure you if you want to go
deeper, how might that change the way you approach your
(11:47):
training? Yeah, think about it.
Could it change how you structure your week, how you
approach hard sessions, or even influence looking into your
running form like those runners in the study who learned to run
softer? What adjustments might you
consider based on knowing more about the impact you're running
creates? Food for thought, especially if
you're keen on optimising form and minimising injury risk.
Maybe exploring date retraining or bio mechanics could be a
(12:10):
really interesting Ave. Definitely worth considering if
you want to maximise your running health and potential.
Welcome to the Deep Dive. We take information you're
curious about and really dig in to find those valuable insights.
That's the plan. Today we're tackling something I
think is, well, really relevant for a lot of you pushing for
better times, maybe like the folks following the 5K runner.
Absolutely. How do you train effectively?
(00:20):
You know, push hard, but withoutconstantly getting injured.
Right. It's the age-old question for
runners, and today we've got some interesting stuff to look
at. Yeah, what's on the menu?
We're looking at Garmin's running tolerance feature,
digging into the science behind impact load and running, and
we'll even touch on how others, like I Measure you, are
measuring this kind of thing. OK, cool.
(00:41):
So the mission is really to get clear on what this running
tolerance thing is, and maybe how you can actually use it to,
well, run smarter. Exactly making that data work
for you. All right, let's start with
Garmin's running tolerance. Then what's the basic idea?
Well, at its core, Garmin developed it to help runners
spot, you know, potentially risky training patterns.
Risky how? Like doing too much too soon?
(01:02):
Sort of, yeah. It's about managing that balance
between stressing your body enough to adapt and improve, but
not overdoing it to the point ofbreakdown.
Getting a better handle on the physical stress, basically.
OK, so it's trying to quantify that stress beyond just how many
mile you run, because we all know a hard tempo feels way
different than an easy recovery jog.
(01:23):
Precisely. And that's where their concept
of impact load comes in. They're trying to measure the
actual mechanical load, the force on your body.
Not just distance. Not just distance.
Think muscles, joints, tendons, the whole system.
The key takeaway isn't just the distance, but the stress.
A short, intense run effectivelycounts for more.
(01:44):
OK, that makes intuitive sense, but how does my watch figure
that out? It's not exactly a bio mechanics
lab on my wrist. No, not quite, but it's pretty
clever. Garmin uses your data weight,
obviously how hard you're running.
Pace, heart rate zones, that sort of thing.
Yeah, intensity metrics and alsorunning dynamics if you've got
the right gear, like a compatible heart rate strap.
So cadence, ground contact time.Exactly, and they even factor in
(02:06):
hills, uphill, downhill. All that gets fed into what they
described as sophisticated tech like a neural network to
estimate the ground reaction forces.
Wow, OK, neural network. So it's estimating the pounding
based on all these inputs. That's the idea, And from that
estimation they calculate what they call equivalent mileage.
Equivalent mileage? What does that mean in practise?
(02:27):
Well, their examples suggest like a tough five mile run with
significant hills might have an impact load equivalent to maybe
8 miles of flat easy running. 8 miles.
OK, that's a big difference. It is, and conversely, maybe an
easy 3 Miller comes out as only 2.5 impact miles.
They also really stressed that downhill running can massively
(02:49):
increase impact. How much?
Potentially up to three times harder than running flat at the
same pace, according to their info.
Three times, right? That definitely feels true
sometimes. So the takeaway is clear, the
type of run dramatically changesthe stress.
Exactly. Short and hard equals more
stress, and you can actually seethis right in Garmin Connect
after a run. Yeah, they provide a chart shows
(03:10):
the impact load throughout the run.
You can see where the spikes were.
Which is useful for understanding which parts were
most demanding. OK.
So that's impact load for a single run, but then there's
acute load and tolerance sounds like they work together.
They do think of acute impact load as the running stress
you've built up recently. It's a weighted sum of the
(03:30):
impact from your runs over the last few days.
Weighted, meaning recent runs count more.
Precisely the impact from yesterday's run contributes more
than the run from five days ago.It reflects that current strain,
how your body is coping right now.
So if impact load is the stress of one session.
Acute load is the running total of stress lately.
(03:51):
You got it Like the current balance on your stress account,
OK. And tolerance, is that like my
credit limit? That's a great analogy,
actually. Yeah.
Tolerance is your body's currentcapacity to handle that acute
load. It's personal based on your
running history. My history like long term.
Both recent and longer term patterns.
It adjusts weekly. If you've been training
(04:14):
consistently, your tolerance, your your credit limit goes up.
If you take time off or reduce volume, it goes down.
Right. So if my acute load, my current
stress balance gets close to or goes over my tolerance limit
alarm bells. It's a caution flag, definitely.
Garmin frames it as a signal to be mindful.
Not necessarily stop running immediately, but more like, hey,
(04:35):
pay attention, maybe ease back. Because consistently going over
that limit is where injury risk climbs.
That seems to be the implication, yes.
Pushing beyond your current capacity repeatedly is asking
for Trump. But wait, you need to push to
improve right? To increase that tolerance.
Absolutely, and the system reflects that.
Consistently training appropriately, challenging
yourself without overdoing it, should gradually increase your
(04:59):
tolerance over time. That's how you build fitness
safely according to this model. And decrease volume tolerance
drops. Makes sense.
Where do I see this on my watch?Usually there's a running
tolerance glance or widget and you can often see it within the
context of your training week summary screen.
Got it. This sounds genuinely useful for
a planet. How does this connect to the the
(05:22):
broader scientific picture of impact and running?
Yeah, great question. This ties in really well with
research like that study reducing impact loading in
runners. OK, what did that study look at?
Well, scientists know that higher vertical impact loading,
basically how hard your foot hits the ground and how quickly
that force travels up your leg, is linked to common running
injuries. Like stress fractures, shin
(05:43):
splints, runner's knee. Exactly.
Fractures, patellofemoral pain, plantar fasciitis.
So this study aimed to see if they could actually teach
runners with high impact forces to run softer.
Teach them how. Through gait retraining, they
measured how hard runners were landing using accelerometers on
their shins. Measuring tibial shock, that
jarring feeling. Precisely tibial shock.
(06:05):
They also measured the vertical impact peak, the Max force, and
crucially, the rate at which that force builds up the
loading. Great.
So how quickly the impact hits, not just the peak force itself?
That sounds like what I measure you looks at too, right?
With their sensors. Yes, exactly.
Similar concept I measure you uses their.
I am used to capture cumulative lower limb impacts and loading
(06:28):
rate is a key factor there too. So how did the retraining work
in the study? They had a control period first,
then the retraining phase where runners got real time feedback
on their tibial shock. Like a beep or a display telling
them if they were landing too hard.
Something like that, yeah. Visual or auditory cues?
Then they gradually faded that feedback out, hoping the runners
would internalise the changes. And did it work?
(06:51):
Did they learn to run softer? Yeah, the results were pretty
impressive. They found significant
reductions in tibial shock, thatvertical impact peak, and those
vertical loading rates. How significant?
Tibial shock dropped by around 32% on average and importantly,
these changes lasted. They checked again a year later
and the runners were still running with lower impact.
A year later? Wow that's sticky.
(07:14):
Did everything reduce? Interestingly, the peak vertical
force didn't change much, which might suggest they weren't
necessarily pushing off less hard, but maybe changing how
they landed to absorb the force more smoothly.
Better mechanics. Fascinating.
And does lower impact mean fewerinjuries?
Did they track that? This specific study focused on
the bio mechanics, but they highlighted the strong link
(07:36):
found in other research. They mentioned a randomised
controlled trial where gait retraining to reduce impact led
to significantly fewer injuries.I think it was something like
62% fewer. 62% OK, that's huge. So the science definitely backs
up the idea that managing impactis critical.
Absolutely, and the study also found correlations between the
(07:56):
tibial shock measured by the sensor and those loading rates,
which kind of suggests that whatwearable devices can measure
might be a decent proxy for these important biomechanical
forces. Which links back to what Garmin
is trying to estimate, and maybeeven to discussions you see on
sites like the 5K Runner about using tech data.
Exactly. It suggests that tracking
something related to impact, even if it's an estimate like
(08:18):
Garmin's or a direct measurementlike I measure use, is valuable.
So Speaking of I measure U, how does their approach compare or
contrast with Garmin's? You mentioned?
They also measure impact load. Right I Measure U uses their
wearable IMU sensors, usually worn on the shins, to directly
quantify the cumulative impacts.Their impact load metric is
(08:39):
essentially calculated from the number of steps multiplied by
the intensity of each impact. So more of a direct count of the
hits scaled by intensity. That's a good way to think about
it. It's a direct measure of the
accumulation of impacts during activity, whereas Garmin is
estimating the overall biomechanical load using a wider
range of inputs like pace, dynamics, elevation and user
(09:01):
profile data fed into their algorithm.
Different paths to a similar goal.
Yeah. Quantifying stress.
Pretty much. It's also interesting that I
measure you distinguishes their impact load from another metric
they have called bone stimulus. Bone stimulus?
How's that different? Impact load is more linear.
More steps or harder steps equals more load.
Bone stimulus tries to model theactual physiological response of
(09:22):
the bone to that loading, which isn't perfectly linear.
Bones respond differently to different patterns and types of
stress. OK, so even more nuanced in how
the body adapts. Exactly.
But the big picture is that bothGarmin, with its integrated
watch features potentially boosted by accessories like the
HRM Pro, and specialised tools like I Measure you are giving
(09:44):
runners ways to understand theseforces.
Which fits right into that goal of smarter training, the kind of
thing someone aiming for A5 KPB,like many following the 5K
runner, would be really interested in.
Totally. It's about having more
information to make better decisions, manage load, stay
consistent, and ultimately perform better.
Consistency is came right and managing impact helps you stay
(10:05):
consistent. Definitely.
OK, let's bring it all together.What are the key practical
takeaways for you, the listener,from all this?
Well, first, if you have a compatible Garmin device, start
actually using the running tolerance feature.
Don't just let it be another data screen.
Pay attention to it, yeah. See how the reported impact load
for different runs, hills, speedwork, easy runs matches how you
(10:26):
feel. Look at how your acute load
tracks against your tolerance over Wix.
Does it make sense with your fatigue levels?
Treated like another feedback signal from your body, but
quantified. Exactly.
But, and this is crucial, it doesn't replace listening to
your actual body. The data is a tool, not the
absolute. Truth precisely If you feel
(10:46):
pain, persistent niggles or excessive fatigue, don't ignore
that just because your watch says your acute load is
productive or within tolerance. Use the data alongside your
intuition and feelings. Point Trust your gut too.
Always. But the science is clear.
Managing impact load is important for staying healthy,
and staying healthy is fundamental if you want to train
(11:06):
consistently and improve, which is obviously a core goal for
performance focused runners. Right, so summing up, Garmin's
Running Tolerance is this tool trying to quantify running
stress using biomechanical principles.
Looking beyond just mileage, science backs up the importance
of managing impact, and other tools like I Measure You offer
(11:26):
different, maybe more direct, ways to measure similar things.
That's a great summary. It all points towards more
informed training. So the final thought to leave
you with how might actively tracking and understanding your
own impact load, maybe using garments features, maybe
exploring other tools like I measure you if you want to go
deeper, how might that change the way you approach your
(11:47):
training? Yeah, think about it.
Could it change how you structure your week, how you
approach hard sessions, or even influence looking into your
running form like those runners in the study who learned to run
softer? What adjustments might you
consider based on knowing more about the impact you're running
creates? Food for thought, especially if
you're keen on optimising form and minimising injury risk.
Maybe exploring date retraining or bio mechanics could be a
(12:10):
really interesting Ave. Definitely worth considering if
you want to maximise your running health and potential.
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