Cardiorespiratory &Fitness
Cardiorespiratory Fitness Score is a composite metric generated by wearable devices and fitness trackers that estimates your cardiovascular fitness level based on continuously collected physiological data. Unlike laboratory VO2 max testing, which requires maximal effort exercise testing with specialized equipment, these scores use algorithms that analyze your heart rate response to daily activities, resting heart rate, heart rate variability, age, sex, and activity patterns to estimate fitness. Popular implementations include Whoop Strain Coach, Apple Watch Cardio Fitness, Fitbit Cardio Fitness Score, and Garmin VO2 Max estimates.
These scores typically correlate well with laboratory-measured VO2 max (r=0.7-0.9) and are often expressed as estimated VO2 max values (mL/kg/min) or percentile rankings relative to age and sex. The algorithms typically improve in accuracy with more data collection over time, learning your individual heart rate patterns and responses to different activity intensities. Some devices require periodic self-reported maximal effort activities (runs, cycles) to calibrate the algorithm, while others passively estimate fitness from daily heart rate patterns.
The revolutionary aspect of wearable-derived fitness scores is continuous, accessible tracking without repeated expensive laboratory testing. Users can monitor fitness trends weekly or monthly, receiving immediate feedback on training effectiveness. While not as precise as laboratory VO2 max testing, these scores provide valuable directional information—improving scores indicate effective training, while declining scores signal inadequate training stimulus or poor recovery. This democratization of fitness tracking enables millions to monitor and optimize their cardiovascular health.
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| Range Type | Level | Clinical Significance |
|---|---|---|
| Correlates well with VO2 max and predicts health outcomes | Provides real-time feedback on training effectiveness | Democratizes cardiovascular fitness monitoring |
| Optimal Fitness Score Ranges | Varies by device;generally 50th percentile for age/sex considered average | 75th percentile or higher (excellent fitness, low health risk) |
| Below 25th percentile (poor fitness, elevated health risk) | Scoring systems vary:Whoop uses percentile ranking by age/sex;Apple Watch uses VO2 max categories (Low, Below Average, Above Average, High);Fitbit uses cardio fitness levels (Poor to Excellent). If expressed as estimated VO2 max:Men >45 mL/kg/min and Women >35 mL/kg/min indicate good fitness. Focus on individual trends over time rather than absolute scores. | Structured Cardiovascular Training |
| Follow periodized training program with 4-5 aerobic sessions weekly combining steady-state cardio (60-75% max HR) and high-intensity intervals (85-95% max HR). Consistency key—fitness scores improve within 4-8 weeks of structured training. Track weekly trends to ensure progressive improvement. | Use Score for Training Optimization | Leverage fitness score trends to optimize training load. Plateauing score suggests need for increased intensity or volume. Declining score despite training indicates inadequate recovery—reduce volume or intensity temporarily. Some platforms (Whoop) provide AI-powered training recommendations based on daily readiness. |
Standard lab range:Varies by device;typically percentile-based or age/sex-adjusted scoring (e.g., Whoop uses percentile ranking)
Validate score changes against real-world performance:race times, power output, perceived exertion at given intensities. Fitness score should correlate with improved performance. If discordant, consider device calibration or algorithm limitations for your activity type.
Monitor recovery metrics (HRV, resting heart rate, sleep quality) alongside fitness score. Overtraining suppresses fitness adaptations despite high training load. Use rest days strategically—fitness scores often peak after recovery periods as adaptations consolidate.
Perform periodic maximal effort activities (5K run, 20-minute all-out cycle) while wearing device to calibrate algorithm. Some devices request these for accuracy. Consider occasional laboratory VO2 max test to validate wearable estimates and ensure accuracy.
Low fitness score (<25th percentile):poor exercise tolerance, early fatigue, shortness of breath with exertion, increased cardiovascular and all-cause mortality risk, reduced quality of life
Sedentary lifestyle, inadequate cardiovascular training, poor recovery, overtraining, chronic stress, inadequate sleep, obesity, cardiovascular disease, aging without exercise
Note: Wearable Fitness Score Validity
Note: Carrier et al., "Validation of Consumer Wearable Fitness Trackers,"JMIR mHealth and uHealth, 2020
Cohort studies using wearable-estimated cardiorespiratory fitness showing similar associations with cardiovascular disease and mortality as laboratory-measured VO2 max, validating clinical utility of consumer wearable fitness estimates.
Source:Quer et al., "Wearable Sensor Data and Self-Reported Symptoms for COVID-19 Detection,"Nature Medicine, 2021
Methodological studies validating submaximal heart rate response to standardized activities for estimating VO2 max. Heart rate recovery and heart rate response to controlled workload provide reliable fitness estimation without maximal testing.
Source:Sartor et al., "Estimation of Maximal Oxygen Uptake via Submaximal Exercise Testing,"Sports Medicine, 2013
Analysis of population-level wearable fitness data revealing opportunities for public health surveillance and individual cardiovascular health optimization. Accessible fitness tracking enables proactive health management at scale.
Source:Althoff et al., "Large-scale Physical Activity Data Reveal Worldwide Activity Inequality,"Nature, 2017
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| Provider | Includes Test | Annual Cost | Total Biomarkers |
|---|---|---|---|
 Superpower | — | $199 | 100+ |
 WHOOP Advanced Labs | ✓ | $349 | 65 |
 Labcorp OnDemand | — | $398 | 30+ |
| — | $486 | 40+ | |
| — | $468 | 83 | |
| — | $798 | 100+ | |
 InsideTracker | — | $680 | 48 |
 Function Health | — | $499 | 100+ |
| — | $900 | 70+ | |
| — | $1150 | 110 | |
| — | $Varies | 75+ |
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs and before making decisions about blood testing.
