Scientific Methodology & Formulas
Peer-Reviewed Consensus · 2026 Edition
Official ZenFit Tools Documentation · Official contact: zenfittools@gmail.com
1. Evidence-Based Physiological Foundations
ZenFit Tools rejects arbitrary rules of thumb in favor of validated clinical formulas published in leading exercise science and clinical nutrition journals. Every calculator implements exact peer-reviewed mathematical models:
- Metabolic Burn: Mifflin-St Jeor (1990) and Katch-McArdle equations validated by the Academy of Nutrition and Dietetics.
- Circumference Anthropometry: US Navy Hodgdon & Beckett (1984) logarithmic regression model adopted by the US Department of Defense.
- Muscular Limits & FFMI: Kouri et al. (1995) 157-athlete baseline study and Dr. Casey Butt’s anthropometric frame analysis.
- Cardiovascular Zones: Tanaka et al. (2001) meta-analysis of 18,712 subjects combined with Karvonen Heart Rate Reserve equations.
- Endurance Pacing: Pete Riegel (1981) fatigue exponent model (T2 = T1 × (D2/D1)^1.06).
- Exercise Expenditure: Ainsworth et al. Compendium of Physical Activities Metabolic Equivalent of Task (MET) database.
2. Transparency & Academic Inquiries
We maintain full transparency regarding all equations, coefficient multipliers, and clinical assumptions. For questions, citations, or academic inquiries, please contact our physiology research team at zenfittools@gmail.com.