Updated 1 week ago Science

The Science Behind the Readiness Score

Explore the scientific evidence behind the Sahha Readiness Score, including why each recovery and strain factor matters and how research supports its connection to performance, fatigue, and resilience.

Readiness is your body and mind’s capacity to perform, recover, and adapt. Sleep alone is not enough to explain it, and neither is activity alone — readiness depends on how well you slept, whether you’re carrying sleep debt, how your body responds to strain, and physiological recovery markers like resting heart rate and heart rate variability. The Sahha Readiness Score synthesises these evidence-backed signals into a single interpretable measure.

The Scientific Model Behind the Readiness Score

The Readiness Score is built on eight evidence-backed factors:

  • Sleep duration: Total time asleep relative to the recommended range.
  • Physical recovery (deep sleep): Time spent in slow-wave sleep, the most physically restorative phase.
  • Mental recovery (REM sleep): Time spent in REM sleep, supporting memory, learning, and emotional processing.
  • Sleep debt: Cumulative shortfall in sleep relative to physiological need.
  • Walking strain capacity: Tolerance for routine low-intensity activity as an early recovery signal.
  • Exercise strain capacity: Tolerance for moderate-to-high intensity effort relative to recovery status.
  • Resting heart rate (RHR): Baseline heart rate as a marker of recovery and physiological strain.
  • Heart rate variability (HRV): Beat-to-beat variation reflecting autonomic nervous system balance.

Each factor reflects a distinct component of recovery and strain tolerance that research links to next-day performance, fatigue, injury risk, and overall resilience.

Sleep Duration

Why it matters Adequate nightly sleep is a foundational driver of next-day alertness, cognitive performance, reaction time, mood, and physical capacity.

What the research shows

  • Adults who sleep 7–9 hours typically perform better on attention, memory, and reaction speed tests than those sleeping less than 6 hours.
  • Each hour of sleep lost below 7 hours is associated with reduced physical work capacity and worse exercise performance the following day.

Why it’s included in the Readiness Score Sleep duration is one of the strongest predictors of next-day physical and mental readiness.

Physical Recovery (Deep Sleep)

Why it matters Deep sleep (slow-wave sleep) is the most physically restorative stage of sleep and supports muscle repair, immune function, tissue growth, and growth hormone release.

What the research shows

  • Adults typically spend about 13–23% of sleep in deep sleep, and reductions in deep sleep are associated with poorer recovery and decreased next-day physical performance.
  • Athletes with better deep sleep patterns tend to recover faster and experience fewer illness and injury disruptions.

Why it’s included in the Readiness Score Deep sleep reflects the body’s physical recovery quality, not just time asleep.

Mental Recovery (REM Sleep)

Why it matters REM sleep supports memory consolidation, emotional regulation, mental flexibility, and cognitive performance — key components of being mentally prepared for daily demands.

What the research shows

  • Adults typically spend 20–25% of sleep in REM.
  • Reduced REM sleep is associated with poorer next-day cognitive performance, slower reaction times, and greater emotional reactivity.
  • REM-rich sleep after learning can meaningfully enhance creative problem-solving and flexible thinking.

Why it’s included in the Readiness Score Mental readiness depends on recovery of cognitive and emotional systems, not just physical recovery.

Sleep Debt

Why it matters Sleep debt is the accumulated impact of consistently sleeping less than needed. Even small nightly deficits compound into measurable performance decline.

What the research shows

  • Two weeks of sleeping 6 hours instead of 8 is associated with cognitive impairment comparable to one full night of total sleep deprivation.
  • Ongoing sleep restriction increases reaction times and reduces attention, memory, and emotional regulation.

Why it’s included in the Readiness Score Cumulative sleep loss strongly predicts fatigue and reduced capacity, even if someone feels fine short-term.

Walking Strain Capacity

Why it matters Reduced tolerance for routine, low-intensity activity (like walking) is an early indicator of under-recovery and reduced readiness.

What the research shows

  • After sleep deprivation, healthy adults often walk slower and report higher perceived exertion for the same task.
  • In overreached states (high load plus inadequate recovery), people show reduced daily movement patterns and increased fatigue.

Why it’s included in the Readiness Score Changes in low-intensity capacity can signal early readiness decline before more obvious symptoms appear.

Exercise Strain Capacity

Why it matters When strain exceeds recovery capacity, exercise performance drops — people fatigue sooner, output falls, and perceived effort rises. This is directly linked to overreaching risk.

What the research shows

  • Under-recovered or overreached athletes show measurable reductions in time to exhaustion, VO2max, and power output.
  • Heart rate during exercise can be elevated and perceived exertion increases for the same workload.

Why it’s included in the Readiness Score Reduced tolerance for moderate-to-high intensity strain is a strong marker of low readiness and elevated injury or illness risk.

Resting Heart Rate (RHR)

Why it matters A higher-than-usual resting heart rate is a sensitive marker of insufficient recovery, stress load, illness, or overtraining.

What the research shows

  • An acute elevation of roughly 5–10 bpm above personal baseline is associated with higher fatigue, reduced performance, and increased risk of illness or injury in athletic and healthy populations.
  • Persistently higher resting heart rate is also associated with higher long-term cardiovascular risk.

Why it’s included in the Readiness Score RHR provides a simple but powerful signal of recovery status and physiological strain.

Heart Rate Variability (HRV)

Why it matters HRV reflects autonomic nervous system balance. Higher HRV generally indicates better recovery and stress resilience, while lower HRV indicates under-recovery or elevated stress.

What the research shows

  • Drops of roughly 10–20 ms below personal baseline are associated with impaired performance and higher fatigue.
  • Day-to-day HRV changes are widely used to detect under-recovery risk and guide training adjustment.
  • Higher HRV is also associated with improved cardiovascular health and stress resilience.

Why it’s included in the Readiness Score HRV is one of the most sensitive markers of readiness and recovery adaptation.

Why a Multi-Factor Readiness Score Matters

No single metric can capture readiness. Two people with similar sleep duration can have very different readiness depending on sleep depth, REM balance, accumulated sleep debt, physiological recovery (RHR and HRV), and current tolerance to strain. The Readiness Score integrates these validated dimensions into a single interpretable measure that reflects real-world recovery and strain balance.

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