Scientific Methodology & Formulas

1. Evidence-Based Physiological Foundations

ZenFit Tools provides educational calculators based on published formulas and references in exercise science and clinical nutrition literature. Each calculator implements published mathematical models with recognized limitations:

• Metabolic Burn: Mifflin-St Jeor (1990) and Katch-McArdle equations evaluated in published nutritional literature.
• 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 & Scientific Inquiries

We maintain full transparency regarding all equations, coefficient multipliers, and mathematical models. For questions, citations, or inquiries, please contact us at zenfittools@gmail.com.