Readiness is your body and mind’s capacity to perform, recover, and adapt. The Readiness Score brings together sleep, activity, and physiological recovery data—each grounded in robust scientific research—to deliver a holistic, actionable measure of how prepared you are for the day’s challenges. Here’s the science supporting every factor in the Readiness Score.

1. Sleep Duration

What is it?

The total time spent asleep each night.

Why it matters:

Adequate nightly sleep is the single most important factor for next-day alertness, physical and mental performance, and recovery from prior strain. Too little or too much sleep impairs cognitive function, mood, reaction time, and physical endurance.

What the science shows:

• Adults who regularly sleep 7–9 hours per night perform significantly better on tests of attention, memory, and reaction speed than those sleeping less than 6 hours (Watson et al., 2015; Belenky et al., 2003).

• Each hour of sleep lost below 7 hours is associated with a significant decrease in physical work capacity and exercise performance the following day (Reyner & Horne, 2013; Fullagar et al., 2015).

• Sleeping less than 6 hours/night increases risk of injury, accidents, and impairs immune function, while chronic short sleep increases the risk of cardiovascular disease by 20–30% (Cappuccio et al., 2011).

2. Physical Recovery

What is it?

Time spent in deep (slow-wave) sleep, the most restorative sleep stage for the body.

Why it matters:

Deep sleep is the most restorative phase for the body, driving muscle repair, immune function, tissue growth, and the release of growth hormone. Higher amounts of deep sleep accelerate recovery from exercise and daily strain, and are vital for optimal physical readiness.

What the science shows:

• Adults typically spend 13–23% of sleep in deep sleep, though this declines with age (Mander et al., 2017).

• Losing just 1 hour of deep sleep per night leads to measurable reductions in muscle recovery, increased perceived fatigue, and decreased next-day physical performance (Skein et al., 2013; Hausswirth et al., 2014).

• Athletes who consistently get more deep sleep show quicker recovery, fewer injuries, and greater improvements in endurance and strength during training periods, compared to those with poor deep sleep (Hausswirth et al., 2014; Leeder et al., 2012).

3. Mental Recovery

What is it?

Time spent in REM (Rapid Eye Movement) sleep, typically associated with dreaming.

Why it matters:

REM sleep is critical for memory consolidation, emotional regulation, and cognitive performance. More REM sleep enhances creativity, mental focus, and stress resilience—crucial components of being mentally prepared for the day’s challenges.

What the science shows:

• Adults typically spend 20–25% of total sleep time in REM sleep (Carskadon & Dement, 2017).

• Each hour less of REM sleep per night is associated with a significant reduction in next-day cognitive performance (Banks et al., 2010; Drummond et al., 2000).

• Reduced REM sleep is linked to slower reaction times, poorer memory, and increased emotional reactivity the next day—even when total sleep duration is unchanged (van der Helm et al., 2011; Drummond et al., 2000).

• REM-rich sleep following learning tasks enhances creative problem-solving and flexible thinking by up to 32%, compared to non-REM-rich sleep (Cai et al., 2009).

4. Sleep Debt

What is it?

The cumulative difference between sleep needed and sleep obtained over several days.

Why it matters:

Carrying sleep debt reduces alertness, impairs reaction time, and weakens both physical and mental performance. Chronic sleep debt is associated with increased risk of illness and injury.

What the science shows:

• Two weeks of just 1–2 hours less sleep per night (sleeping 6 hours instead of 8) is associated with a cognitive performance deficit equivalent to one night of total sleep deprivation (Van Dongen et al., 2003).

• Accumulating sleep debt over a week (less than 6 hours/night) increases reaction times by up to 30% and impairs attention, memory, and emotional regulation (Van Dongen et al., 2003; Banks & Dinges, 2007).

• Each night of <6 hours sleep increases risk of injury and illness, and chronic sleep debt is associated with a higher risk of cardiovascular disease and increased risk of metabolic dysfunction (Cappuccio et al., 2011).

5. Walking Strain Capacity

What is it?

An index of how well your body can handle routine low-intensity activity (e.g., walking), based on recent patterns and recovery.

Why it matters:

Reduced capacity to handle normal daily walking is an early sign of poor recovery, elevated strain, and lower readiness for both physical and cognitive challenges. It can signal the need for rest or lighter activity.

What the science shows:

• After a single night of sleep deprivation, healthy adults walk 8–14% slower and report 20–30% more perceived exertion for the same walking task, compared to when rested (Temesi et al., 2013; Good et al., 2018).

• Athletes in a state of overreaching (high training load, inadequate recovery) show a reduction in daily step count and self-selected walking speed, and report greater fatigue, compared to when well-recovered (Hausswirth et al., 2014; Millet et al., 2011).

• Impaired walking performance after high strain is predictive of greater risk for injury, illness, and poor training response in both athletes and the general population (Hausswirth et al., 2014; Good et al., 2018).

6. Exercise Strain Capacity

What is it?

Your current capacity to tolerate and recover from moderate-to-high intensity exercise.

Why it matters:

When strain exceeds your body’s ability to recover, your exercise capacity declines: you tire more quickly, your maximum output drops, and perceived effort rises. This is a direct marker of poor readiness and high risk for injury, illness, or burnout.

What the science shows:

• Athletes who are overreached or under-recovered after periods of high training load show a 7–21% reduction in time to exhaustion, maximal aerobic capacity (VO₂max), and power output compared to their well-recovered baseline (Meeusen et al., 2013; Hausswirth et al., 2014).

• Perceived exertion increases by 15–30% for a given exercise intensity after inadequate recovery, and heart rate during exercise is elevated by 5–10 bpm (Hausswirth et al., 2014; Meeusen et al., 2013).

• Frequent, large drops in exercise strain capacity (compared to your normal baseline) are a strong predictor of overtraining syndrome and higher risk of illness or injury (Meeusen et al., 2013).

7. Resting Heart Rate (RHR)

What is it?

Your lowest heart rate during rest, typically measured during sleep or upon waking.

Why it matters:

A higher-than-usual resting heart rate is a sensitive, early marker of insufficient recovery, stress, illness, or overtraining. Consistently lower RHR is associated with better cardiovascular health, higher fitness, and improved readiness for physical and mental tasks.

What the science shows:

• An acute increase of just 5–10 beats per minute (bpm) in resting heart rate compared to your personal baseline is associated with significantly higher fatigue, reduced exercise performance, and increased risk of injury or illness in athletes and healthy adults (Bosquet et al., 2008; Le Meur et al., 2013).

• RHR is a sensitive day-to-day marker of recovery: Elevated RHR after high-intensity activity or poor sleep signals a need for more rest and lower strain (Le Meur et al., 2013; Stanley et al., 2013).

• Consistently lower RHR (50–60 bpm for most adults) is associated with a 30–40% lower risk of cardiovascular disease and mortality compared to higher RHR (≥70 bpm) (Jensen et al., 2013).

8. Heart Rate Variability (HRV)

What is it?

A measure of the variation in time between each heartbeat; reflects the balance between the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) nervous systems.

Why it matters:

Higher HRV is a sign of robust recovery, lower stress, and good adaptation to physical and psychological strain. Lower HRV indicates poor recovery, ongoing stress, or a need for rest—making it a powerful readiness biomarker.

What the science shows:

• A decrease in HRV of 10–20 ms below your personal baseline is associated with impaired performance, higher fatigue, and increased risk of illness or injury (Plews et al., 2013; Stanley et al., 2013).

• Day-to-day HRV is one of the best predictors of readiness: Lower HRV after high training loads or poor sleep reliably signals under-recovery and higher risk of overtraining (Plews et al., 2013; Stanley et al., 2013; Shaffer & Ginsberg, 2017).

• Individuals with consistently higher HRV (e.g., RMSSD > 60 ms) have 20–40% lower risk of cardiovascular disease and better stress resilience than those with low HRV (RMSSD < 40 ms) (Jarczok et al., 2015).
  
  

Conclusion

The Readiness Score is more than just a daily number—it’s a science-driven reflection of your body’s balance between recovery and strain. Each factor is grounded in research, providing you with actionable insights to optimize performance, avoid overtraining, and support your overall well-being.

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