Recovery Score
The Recovery Score is your daily readiness indicator — a number from 0 to 100 that tells you how prepared your body is to handle training stress today.
The science of recovery
Recovery in athletes is primarily driven by the autonomic nervous system (ANS). When you are well recovered, the parasympathetic (rest-and-digest) branch dominates. When you are stressed or fatigued, the sympathetic (fight-or-flight) branch is more active.
Heart rate variability (HRV) — specifically the RMSSD metric — is the most validated non-invasive proxy for parasympathetic tone. Research consistently shows that higher morning RMSSD relative to your personal baseline is associated with greater readiness and better athletic performance, while suppressed RMSSD signals accumulated fatigue or impending illness.
Resting heart rate (RHR) provides a complementary signal: an elevated RHR above your personal norm indicates that your cardiovascular system is working harder than usual to maintain homeostasis — a common sign of under-recovery or physiological stress.
What Flux uses to calculate your score
Flux combines multiple physiological signals. Each signal is compared to your personal 40-day rolling baseline — so the score reflects your norms, not population averages.
HRV (RMSSD)
Your morning heart rate variability is the most heavily weighted input. It reflects how well your autonomic nervous system has recovered overnight. Flux compares today's reading against your personal rolling average.
Resting Heart Rate
Your morning resting heart rate from your first reading after waking. An elevated RHR adds a negative adjustment to the score; a low, stable RHR contributes positively.
Sleep Score
Poor sleep quality often precedes reduced HRV the following morning. Flux incorporates the previous night's Sleep Score as a supporting input when available.
Respiratory Rate
Overnight breathing rate from Apple Health. A significantly elevated respiratory rate compared to your baseline can be an early indicator of illness or high stress, and adjusts the score accordingly.
Your personal baseline and initial calibration
Recovery is inherently individual. A morning RMSSD of 45 ms might be excellent for one person and below average for another. For this reason, Flux tracks your rolling baseline over the last 40 days and evaluates each measurement relative to your history, not a generic population reference.
Flux requires a minimum of 4 days of consistent morning HRV readings to calibrate your personal baseline and provide your first Recovery Score. This means the score becomes more accurate over time, as Flux accumulates more data about your personal physiology. The more readings you provide, the more reliable the baseline becomes.
Interpreting your Recovery Score
Your body is primed for high-intensity training or competition. This is the optimal window to push harder.
You can train, but consider moderate intensity. Your body is recovering but not yet fully ready for peak effort.
Prioritise rest or active recovery. Pushing through low recovery days increases injury risk and compounds fatigue.
How to improve your recovery
- Prioritise 7–9 hours of quality sleep consistently.
- Avoid alcohol in the evening — it significantly suppresses HRV and deep sleep.
- Manage training load: alternate hard days with easy or rest days.
- Control stress through breathing exercises, meditation, or cold exposure.
- Stay hydrated and maintain consistent meal timing.
- Take your morning HRV reading at the same time each day, before getting up.