What?
Last week, Apple introduced a readiness score for the Watch Series 12 and Ultra 4. This score combines your activity, sleep, and vital signs into a number from 0 to 10, with advice like “Recover” or “Go For It.” According to Apple, it can help you plan your workouts and daily routine.
The new heart-rate sensor is backed by solid evidence. In a study by Apple with 1,254 participants, the Series 12 showed lower heart-rate errors than six competing devices during workouts and daily activities.
That study only measured heart rate. It did not test if following the readiness recommendations actually improves fitness. From the public sources I checked up to September 15, I did not find any trials that answer this question for Apple’s new score.
So what?
I want to correct something from my recovery series. I said heart rate variability, or HRV, was “the single most reliable indicator of recovery status.” That was too strong. I also gave too much credit to what a morning reading can tell us about brain recovery.
HRV measures the variation in time between heartbeats and can help guide training. In a 2021 trial by DeBlauw with 55 adults aged 18 to 35, the group using HRV had fewer hard training days. Both groups improved, but there was no clear difference in fitness gains. Since this was a small trial with a set training plan, it might have missed some differences.
This gives me a good reason to use HRV: it can help decide when to take it easy during a tough session. However, the trial doesn’t show that Apple’s score can make that choice.
I recommend using your training plan as a starting point. Use the score as a reminder to check your sleep, symptoms, and recent effort before making any changes.
Now what?
Before your next workout:
Look at the details behind your score. See what changed in your sleep, activity, or vital signs. Make sure the recorded sleep and exercise match what you actually did.
Write a sentence about how tired or sore you feel and how you have been sleeping. Add anything else that feels unusual.
If you get a low score and also feel unusually tired or have slept poorly, pick the easier option in your plan. If your score and how you feel do not match, check the data before changing your session. If you are still unsure, go with a lighter workout.
If you are worried about any symptoms, talk to a doctor before exercising, no matter what your score says. Apple’s instructions also note that the score doesn’t account for all health conditions or medications and should not be used alone to decide whether it is safe to exercise.
My practical advice is to take it easy if you are unsure about a session. This checklist has not been tested as a protocol for Apple’s score.