Garmin – Training Readiness 100 Prime
A couple of weeks ago both Training Today (Apple Watch) and Training Readiness (Garmin Forerunner 965) indicated I was perfectly ready to train.
Except I wasn’t. I had shingles which is a viral infection that can affect the nervous system and, in my case, it caused significant and persistent pain that stopped me from exercising.
My sense of readiness would have been as this image shows (from a different day!)
Garmin Training Readiness – It’s Not Fully Accurate
Garmin’s Training Readiness assesses an individual’s readiness level based on a composite metric derived from five primary factors:
- Sleep score – evaluates the quality of sleep based on duration, sleep stage distribution, and autonomic nervous system recovery data.
- Recovery time – indicates when the body is expected to recover from the last activity fully, considering its strenuousness and other contributing factors.
- Acute training load – measures the impact of recent activities on current fitness levels.
- HRV status – assesses the balance of heart rate variability, reflecting the body’s ability to handle stress effectively.
- Stress history – accounts for stress levels from the past three days while an individual is awake, which can affect training readiness and overall performance.
It is continually updated with significant changes occurring in the morning as sleep score, HRV status, sleep history, acute training load, and stress history are updated. A simple numeric score is given on a 1 to 100 scale
Sources of Inaccuracy
There are many sources of inaccuracy.
The quality of the raw data is a good place to start. Garmin’s latest Elevate 5 sensor is found on the Epix 2 Pro/Fenix 7 Pro and will be added to other Garmin devices going forward. The likes of dcrainmaker have found it accurate during endurance sports and Fit Gear Hunter is impressed with its accuracy during gym/X-Fit activities.
However, if an optical HR sensor accurately records HR during a workout, it does not mean HRV will be recorded correctly at rest. It is quite possible that HRV can be recorded correctly at rest but the same sensor is useless to record workouts and vice versa. The Quantified Scientist is not convinced that there is much improvement over Garmin’s Gen 4 sensor and also finds that the deep sleep correlations Garmin generates are not great.
Q: Does any of that matter?
A: Yes.
Your acute training load (ATL) is a short-term measurement of the load placed on your body by exercise taken from either a power meter or heart rate monitor. If your optical sensor and Zones are ‘about right’ the ATL will be ‘correct enough’ in my experience.
Next, we look at your HRV, a measurement of how your body handles stress in its widest sense – including exercise stress and general daily stress. Garmin takes this data from its optical sensor and the key measurement is based on the average of your night’s sleep. This IS a scientifically correct method to use. Some factors can make the interpretation incorrect:
- Latency – how long do you take to get to sleep? How accurate are the start and end sleep points that Garmin uses? If you lie in bed reading for an hour Garmin may well assume you are asleep… that’s your fault and not Garmins! I DO expect Garmin to be accurate but I don’t expect them to perform miracles.
- Skewing of HRV – late evening activities impact HRV more in the first few hours of sleep. This could be from drinking alcohol or simply eating late; in those cases, HRV averages are lowered.
- Latency and skewing can be eliminated if you take a 1-3 minute manual reading every morning with a chest strap and a proper tool like HRV4Training. However, Garmin has a fully automated overnight data collection process which is the only practical solution for most people. In any case, using nightly HRV averages is scientifically valid.
- Incorrect determinations in sleep stages – The Quantified Scientist’s analysis against a polysomnograph (PSG, below) raises concerns that Garmin is much less reliable at accurately recording HRV during Deep Sleep. This is the physical regenerative phase of sleep and is the most important one to get right. Note that I’m not talking here about Garmin incorrectly identifying Sleep Stages, more so the accuracy defined within that period. I’ve not seen any analyses that show how impactful the calculations made in deep sleep are on the overall average. WHOOP used to focus its data gathering more on those periods of sleep before changing to a similar method as Oura/Eight Sleep.
- HRV algorithms – Garmin uses widely accepted algorithms where its nightly HRV average is assessed against a multi-week moving average (your baseline range). Garmin is correct here.
Then we have the tinkering in the daytime. Garmin appears to use HRV readings taken during the day to boost or degrade readiness. My understanding is that this is somewhat of a made-up concept. It’s wrong.
Then we come to the single-number assessment of your entire training readiness. It’s great that it’s a simple percentage number. Everyone can understand that. However, I would challenge Garmin and all the other tech vendors to show the science behind how they add together all these disparate measures. AFAIK they are not additive. It’s wrong.
Garmin has missed a trick by excluding ‘feel’ from the calculation. At the end of every workout on most high-end Garmins, you can now assign your RPE and FEEL to each workout. Garmin could use a similar approach to assess how you feel when you wake up and add that to the readiness score. But then, of course, it’s just yet another factor that can’t be combined with the others!
Take Out
If you feel awful…don’t trust the tech!
Hopefully, the information above explains why your Garmin readiness reading might be incorrect. Keep using it but treat it with caution.
I regularly use Garmin readiness but have other HRV/readiness tools including WHOOP, Oura, HRV4Training, Athlytic (Apple Watch) and Eight Sleep. They’re all pretty good and, in my opinion, even better when they all agree with each other 😉 WHOOP and Oura are more easily worn and HRV4Training is probably the most correct. I especially like Eight Sleep as it gives scientifically validated nightly HRV averages and adjusts bed temperatures to boost HRV and recovery
Bottom Line For HRV
- HRV is a measure of how your body handles stress.
- Low HRV isn’t necessarily bad.
- Accurate data is best sourced from quality chest straps like a Polar H10 but even your iPhone’s camera light can be used to give scientifically valid data (Source: Altini)
- Accurate sampling periods should be consistently taken and be for the entire night or a 1-5 minute waking reading. The former is easily automated, and the latter helps exclude the effects of late-evening events.
- Your daily HRV should lie within a range determined from about 3 weeks of readings and continually updated. Act when it goes out of range.
- Too many factors affect HRV during the day for it to be meaningful.
More: A detailed guide on HRV by Marco Altini, hosted on this site.
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Was ist mit einer garmin 975 gibt es da schon was?
IDK, i dont think so until next year
I’ve recently started to question the value of scores like ‘training readiness’, sleep, and stress on devices. Are these anti-features that we should consider disabling? Wouldn’t it be more beneficial to spend 30 seconds every morning sitting on the side of the bed, jotting down notes about how we feel, and doing the same every night before bed? This practice would encourage mindfulness and self-reflection, helping us tune into our own bodies and emotions without relying on a device.
Is there any scenario where glancing at a watch might be better than this more personal, introspective approach for casual athletes? Doesn’t it all come down to creative ways to extract money from us for features that are at best of little use, at worst could be helping us lose touch with our on insight?
for a decade or so I triangulate TSB (modelled readiness) with HRV (body response) and FEEL (subjective, holistic) to determine changes to planned training I don’t see any reason for me to change!
Garmin Training Readiness is useful. It does help bring your attention to potentially negative factors that are present in its inputs.
I think the danger is that some people might follow it unquestionably.
Curious how you do that as far as methodology?
🙂 I just look at them
TSB based on ATL/CTL from HR across the tri sports
HRV admittedly now confused because I look at several tools (I don’t recommend anyone to look at multiple products, maybe two at most…one that does morning readings and one that does nighlty averages.)
Feel…is feel
I have found the opposite to be true. On some of the days where it said my training readiness was low and I should rest, sometimes due to drinking, sometimes not, I went out and had an amazing run. I love the watch, I love the features, but without objectively knowing how you physically feel it will never be 100% accurate. When I wake up I sometimes try to guess what my scores might be based on how I feel, and the watch tends to match.
Side note, as far as accuracy goes I started wearing my watch 2 fingers above the wrist bone and accuracy during the day and night increased significantly. Wearing it in the typical watch spot causes inaccurate readings with wrist flexion. It looks weird, but I am used to it now.
yes that is the best place to wear it. ie a place where people don’t usually wear a watch!! oh well!
the problem that some skinnier people have wearing it higher on the forearm is that it slips down to the wrist and then is very loose.
accuracy: again I remind readers that just because oHR is accurate it doesn’t mean that HRV will be accurate. That depends on other factors including the filtering algorithms that garmin use to get the raw metics. Garmin then use other algorithms to build on the raw data. training Readiness is a further, compounded metric that pulls together, ranks and assigns importance to its constituents.
So that’s what Garmin said, what did Oura (and others) say?
I find my Oura, which I have been using since January, is always telling me I am prime and ready to go. Very little variation in its feedback.
I showed the Training Today on Apple watch which is based on HRV at approx 15 minute intervals
Those based on HRV will likely show the same thing.
Are there any specific sports or activities that benefit most from Garmin’s Training Readiness feature? Regard Telkom University