Some mornings your body is ready for a hard session, and some mornings it's still recovering from the last one. Training readiness is a daily score that tells them apart. It combines recovery signals, mainly heart rate variability (HRV), resting heart rate (RHR), and sleep, often with your recent training, into one number for how well-recovered you are and how much hard training you can absorb today. A high score suggests you can productively handle high-intensity work. A low score says recovery should come first.
How Readiness Scores Work
You get fitter from the stress of your workouts and the recovery between them. A hard session on a fully recovered body produces a strong adaptation signal. Do the same session while fatigued and the adaptation is blunted, with more risk of injury, illness, and overreaching.
Readiness scores put a number on that recovery instead of relying on "I feel okay" or "I feel tired." The physiology underneath is your autonomic nervous system. A well-recovered body shows high parasympathetic tone: higher HRV, lower resting heart rate, and consolidated sleep. A fatigued body shows sympathetic activation: suppressed HRV, elevated RHR, and fragmented sleep.
Every app combines the inputs differently (FITIV's method is below). HRV is usually the most sensitive. Readiness systems compare last night's HRV with your own typical range rather than a population norm, so a reading well below your usual level pulls the score down. Several low readings in a row mean more than one low night.
Resting heart rate is also compared with your own normal. A few beats above your usual level can reflect fatigue, illness, or stress. RHR responds more slowly than HRV, so an elevation that lasts several days is more meaningful than one high morning.
Sleep covers how long and how well you slept. Adequate sleep is the most important non-training factor in recovery, and short or fragmented nights tend to lower readiness. Many readiness scores, including FITIV's, also account for how hard you've trained over the past few days.
Interpreting readiness scores:
- 75–100: High readiness. Parasympathetic dominant, well-recovered. Pursue planned high-intensity sessions without modification.
- 50–74: Moderate readiness. Body is partially recovered. Aerobic and moderate-intensity sessions appropriate; consider reducing or skipping high-intensity elements.
- Below 50: Low readiness. Significant recovery deficit. Prioritize rest, sleep, and nutrition. A hard session on a day like this costs more and is less likely to pay off.
What suppresses readiness:
- Hard training (especially cumulative load over days)
- Poor sleep (duration and/or quality)
- Alcohol (it lowers overnight HRV and raises resting heart rate, more so at higher amounts)
- Illness or immune activation
- Significant psychological stress
- Travel and jet lag
- Heat stress and dehydration
- Caloric deficit or under-fueling
How Training Readiness Relates to Training
In HRV-guided training, you adjust intensity based on daily readiness instead of following a rigid calendar. In controlled studies, this has improved endurance at least as much as fixed-schedule training (Manresa-Rocamora et al., 2021). The idea is that hard sessions are absorbed better on high-readiness days than on low ones. A typical case: intervals are on the calendar and your score comes back Low. Swapping in an easy aerobic session and moving the intervals to a higher-readiness day is this kind of adjustment.
Readiness can also warn you about overtraining. A score that stays low for several days in a row can be an early sign of functional overreaching, sometimes before you feel tired. Catching it early lets you cut volume before performance starts to drop.
Across a training block, the trend shows whether the load is right. If readiness trends upward during a build block, you're absorbing the training. If it keeps falling without recovery days, the load is too much.
How FITIV Uses Training Readiness
FITIV Pulse generates Training Readiness from the overnight data your Apple Watch (or a connected Garmin or Fitbit) records, with no manual measurement needed. It works in two steps:
1. Recovery score. When you wake up, FITIV scores your recovery from 0 to 100. It looks at your overnight HRV, resting heart rate, respiratory rate, blood oxygen, and wrist temperature compared with your own typical range, along with your Sleep score.
2. Training Readiness. FITIV then combines your Recovery score with:
- Recent strain and workouts: your activity from the past few days, with recent efforts counting more. High strain may lower readiness
- Battery: low energy reserves reduce readiness
- Training load ratio: your recent workload compared with your long-term fitness trend. A well-balanced load supports higher readiness, while a sharp spike lowers it
Readiness updates through the day as your Strain and Battery change.
The score appears on FITIV's Today tab and in the FITIV Apple Watch app, in five levels, each with a plain-language recommendation:
- Prime (90–100): "Your metrics are on point" (ideal for an intense session or a personal-best attempt)
- High (75–89): "Time to challenge yourself"
- Moderate (50–74): "You're in a good spot for a solid workout"
- Low (25–49): "Focus on light activity"
- Poor (0–24): "Your body needs rest"
If there's no sleep recorded for the night (for example, you didn't wear your Apple Watch to bed), there's no Recovery score that day. Readiness still runs on your strain, Battery, and training load, and FITIV will suggest tracking sleep to get the full picture.
Frequently Asked Questions
Why does my readiness score vary so much from day to day?
HRV, usually the most influential input to readiness scores, is sensitive to things that change daily: sleep, alcohol, stress, late meals, travel, and recent training. Noticeable swings between nights are normal. FITIV compares each night's HRV with your own typical range, so one unusual night can move your score. Look at the trend over several days before changing your training plan, and check whether anything unusual happened the night before.
My readiness score is low but I feel fine subjectively — should I train hard?
Use both signals. How you feel is a genuinely useful measure: a systematic review of 56 studies found that athletes' self-reported well-being tracked their training load more reliably than common objective measures (Saw et al., 2016). A single low score when you feel great is often noise, and an important session can reasonably override a Moderate score. A Low or Poor score (below 50) for several days in a row is harder to dismiss, especially if your sleep, mood, or motivation are also slipping.
Can I improve my readiness score?
Yes, by improving the inputs. The changes that usually help most are getting more sleep and keeping it consistent, building training load gradually, cutting back on alcohol, managing stress, and eating enough to fuel your training. FITIV's readiness history lets you see how your scores respond over the following days and weeks.
