📐 Methodology & Sources

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.