Methodology & Sources

Not medical advice. Fit PA is a fitness tracking and coaching tool, not a medical device. It does not provide medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making medical decisions or starting a new exercise program.

Fit PA's training metrics, zones, and coaching guidance are built on established, peer-reviewed sports-science methods. The references below describe the general scientific basis for those calculations, for transparency.

Training load & intensity

Training Stress Score, Intensity Factor, and Normalized Power follow the power-based training-load framework:

Allen H., Coggan A., McGregor S. — Training and Racing with a Power Meter (VeloPress).
The Science of the Performance Manager — TrainingPeaks (TSS / IF / PMC overview).

Fitness, fatigue & form (CTL / ATL / TSB)

Banister E.W. — the impulse-response (fitness–fatigue) model of training adaptation.
Performance Management Chart — chronic load (CTL), acute load (ATL), and training-stress balance (TSB = CTL − ATL).

Heart-rate training zones

Karvonen method — heart-rate-reserve zone calculation.
American College of Sports Medicine — ACSM's Guidelines for Exercise Testing and Prescription.

Pace, threshold & VO₂max

Daniels J. — Daniels' Running Formula (VDOT) (Human Kinetics).
Riegel P.S. (1981) — Athletic Records and Human Endurance, American Scientist (endurance time-prediction model).

Grade-adjusted pace

Minetti A.E. et al. (2002) — Energy cost of walking and running at extreme uphill and downhill slopes, Journal of Applied Physiology.

Recovery & readiness

Heart-rate-variability-guided training research (e.g., Plews D., Buchheit M. et al.) — using HRV alongside training-load balance, sleep, and resting heart rate.

Exercise safety

World Health Organization — Physical activity guidelines.
American Heart Association — Recommendations for physical activity in adults.

Reminder. These references describe the scientific basis for Fit PA's calculations and coaching. They are provided for transparency and are not medical advice. For any decision that affects your health, consult a qualified healthcare professional.