Methodology
The science behind Run Studio's calculations
Run Studio builds on decades of peer-reviewed exercise physiology research, combining established methodologies with modern refinements. Our calculations are based on well-documented formulas from trusted sources, with improvements informed by recent research and community feedback. We cite all scientific sources while our specific improvements remain proprietary. Below, we explain the scientific foundation for each calculator and reference the research behind it.
VDOT (Jack Daniels)
Our VDOT calculations use Jack Daniels' Running Formula, the gold standard for running performance analysis since the 1970s. VDOT represents a runner's aerobic capacity adjusted for running economy, providing a single number that accounts for both fitness and efficiency.
Source: Daniels, J. (2013). Daniels' Running Formula (3rd ed.). Human Kinetics.
VO2max Estimation
While VDOT and VO2max are related, they're not identical. We calculate VO2max using the ACSM metabolic equations for running, which consider speed, grade, and energy cost of running (Cr).
Our enhancement: We apply ability-based adjustments to running economy, recognizing that elite and recreational runners have different energy costs. Elite runners typically demonstrate better running economy (lower energy cost per distance), while recreational runners show higher costs. This multi-level approach provides more accurate VO2max estimates across all fitness levels.
We also use duration-based adjustments for the fraction of VO2max sustainable during races. Shorter races allow athletes to sustain a higher percentage of their VO2max compared to longer efforts.
Sources:
• American College of Sports Medicine (2018). ACSM's Guidelines for Exercise Testing and Prescription (10th ed.)
• di Prampero, P.E. (1986). The energy cost of human locomotion on land and in water. International Journal of Sports Medicine, 7(2), 55-72.
Why Ranges Instead of Single Times
Traditional race predictors provide a single time, but real performance varies based on training specificity, race day conditions, pacing execution, and individual strengths. We provide three predictions (best/likely/slow) to give you a realistic range for race planning and goal setting.
Ability-Based Variance
Elite runners demonstrate more consistent performance across distances compared to recreational runners. Our algorithm adjusts prediction ranges based on fitness level—higher-level athletes see tighter ranges reflecting their more predictable race outcomes, while recreational runners see wider ranges that account for greater performance variability.
Distance-Specific Adjustments
Longer races introduce more variables that affect performance—nutrition strategy, pacing discipline, mental fatigue, and training specificity all play larger roles. Prediction ranges progressively widen for longer distances, with marathons having significantly wider ranges than shorter races. A 5K specialist predicting a marathon will see appropriately wider uncertainty compared to predicting a 10K.
Important: Predictions assume distance-specific training. Using a 5K time to predict a marathon requires appropriate marathon-specific training to achieve those predicted times.
Foundation: Base predictions use Jack Daniels' VDOT method. Variance calculations are our proprietary enhancement to provide more realistic race planning guidance.
Why Ranges Instead of Single Paces
Traditional calculators provide exact paces for every training zone (e.g., "Threshold = 6:45/mi"). Run Studio provides ranges for all training intensities.
Why we do this:
- •Training adaptations occur across zones, not at single magic paces
- •Real-world conditions vary daily (weather, fatigue, fueling)
- •Elite coaches prescribe ranges, not rigid numbers
- •Reduces pace obsession while maintaining scientific validity
Our approach acknowledges that hitting the right physiological stimulus is more important than hitting an exact pace. A successful threshold workout is one that stresses your lactate system appropriately—not one where you obsess over hitting 6:45/mi instead of 6:48/mi.
Building on Jack Daniels' Precedent
Jack Daniels already prescribed ranges for Easy pace (62-70% VDOT) in his training tables—acknowledging that recovery runs naturally vary based on fatigue and conditions. We've extended this practical, proven approach to all training zones based on modern exercise physiology research and coaching best practices.
Range Calibration
We calibrate each zone's range based on peer-reviewed exercise physiology research, coaching best practices, and what variance still delivers the intended training adaptation. Range sizes differ by zone—some intensities (like CV) require tighter ranges, while others (like Repetition) allow more flexibility.
The specifics of our range calculations are proprietary, but the science is sound and grounded in established training principles.
CV & VO2max Paces
Critical Velocity (CV): ~96% of 5K pace - the threshold between sustainable and unsustainable effort
VO2max Pace: ~100% of 5K pace - optimal intensity for developing maximum oxygen uptake
These replace Daniels' generic "Interval" pace with more precise, research-backed targets.
Source: Jones, A.M., Vanhatalo, A., et al. (2010). Critical power: Implications for determination of VO2max and exercise tolerance. Medicine & Science in Sports & Exercise, 42(10), 1876-1890.
Foundation: Jack Daniels' intensity zones, modern interval training research, and practical coaching wisdom.
Altitude affects running performance due to reduced oxygen availability. We use the research-backed formula from Wehrlin & Hallén (2006), which quantifies the performance decline at various elevations for middle-distance running events.
We adjust for both scenarios: training high/racing low, or training low/racing high.
Source: Wehrlin, J.P., & Hallén, J. (2006). Linear decrease in VO2max and performance with increasing altitude in endurance athletes. European Journal of Applied Physiology, 96(4), 404-412.
Running uphill or downhill significantly changes the energy cost compared to flat ground. We use the ACSM VO2 formula for running on grades, which accounts for the additional vertical work required when ascending and the reduced energy cost (with eccentric muscle demands) when descending.
Grade Adjusted Pace (GAP) converts your actual pace on hills to the equivalent flat-ground pace, helping you understand true effort level during hill training and ensuring you don't over or undertrain.
Our calculations account for both uphill and downhill grades, recognizing that downhill running is easier aerobically but creates eccentric muscle stress.
Sources:
• American College of Sports Medicine (2018). ACSM's Guidelines for Exercise Testing and Prescription (10th ed.)
• Minetti, A.E., et al. (2002). Energy cost of walking and running at extreme uphill and downhill slopes.Journal of Applied Physiology, 93(3), 1039-1046.
Running on a treadmill differs from outdoor running primarily due to the absence of air resistance. Research shows treadmill running is easier at faster paces, with the difference becoming more pronounced as speed increases.
Our calculator provides two modes: setting treadmill incline to match outdoor effort, or calculating what your treadmill pace translates to outdoors. We use pace-dependent conversion formulas that account for the relationship between running speed and air resistance effects.
Sources:
• Jones, A.M., & Doust, J.H. (1996). A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. Journal of Sports Sciences, 14(4), 321-327.
• Conversion formulas adapted from hillrunner.com research
Official BAA Standards
We use the official Boston Athletic Association qualifying standards for 2026 and 2027, which vary by age group and gender. These standards are updated whenever the BAA announces changes.
Historical Acceptance Probability
Unlike other calculators that simply tell you if you qualify, we calculate your actual probability of acceptance based on historical cutoff data. Meeting the BQ standard doesn't guarantee entry—recent years have seen cutoffs ranging from no buffer to nearly 8 minutes under the qualifying time.
Our probability calculation uses 6 years of actual BAA cutoff data to show how often your predicted time would have been accepted historically. This gives you realistic expectations rather than false confidence from simply "qualifying."
Safe Target Recommendation
We provide a "safe target" time that accounts for historical cutoff variability. This conservative target is based on analysis of past acceptance rates, giving you a realistic goal that maximizes your chances of entry.
Source: Boston Athletic Association official qualifying times and historical registration data (2021-2026). baa.org
We support multiple heart rate zone calculation methods to accommodate different training philosophies:
- •Percentage of Max HR: Traditional zones based on percentages of your maximum heart rate
- •Heart Rate Reserve (Karvonen): More individualized method accounting for resting heart rate, providing zones that better reflect actual exercise intensity
- •Training Pace Integration: We map heart rate targets to Jack Daniels' training paces, showing appropriate HR ranges for Easy, Marathon, Threshold, and CV intensities based on your chosen method
Sources:
• Karvonen, M.J., Kentala, E., & Mustala, O. (1957). The effects of training on heart rate: A longitudinal study. Annales Medicinae Experimentalis et Biologiae Fenniae, 35(3), 307-315.
• Daniels, J. (2013). Daniels' Running Formula (3rd ed.). Human Kinetics.
Dew Point Calculation
Heat stress affects running performance due to thermoregulation demands. We use a dew point-based approach, which combines temperature and humidity into a single metric that better reflects the body's ability to cool itself through evaporation.
Dew point is calculated using the Magnus-Tetens approximation, accurate for normal running temperatures.
Performance Impact
Heat stress affects performance when dew point exceeds 60°F (~1.5 sec/mi per °F above 60°F). This translates to approximately 0.025% VDOT reduction per 1°F dew point above the 60°F threshold. When both altitude and heat adjustments apply, the pace penalties are added together.
Sources:
• Magnus, G. (1844). Versuche über die Spannkräfte des Wasserdampfs. Annalen der Physik, 137(2), 225-247. (Magnus-Tetens formula for dew point)
• Ely, M.R., et al. (2007). Impact of weather on marathon-running performance. Medicine & Science in Sports & Exercise, 39(3), 487-493.
• Galloway, S.D.R., & Maughan, R.J. (1997). Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man. Medicine & Science in Sports & Exercise, 29(9), 1240-1249.
Exercise physiology research continues to advance. We regularly review new studies and incorporate validated findings to improve our calculations. Community feedback from runners and coaches also helps us identify areas for refinement.
If you notice discrepancies, have questions about our methodology, or know of relevant research we should consider, we welcome your input at run@introversion.ai