Who built this
My name is Varun U.. I’m a software developer based in Bengaluru, India, and I’ve been running consistently for the better part of two years. I run 3–4 times a week, primarily on roads, targeting marathon-distance races. I’ve completed a full marathon and regularly race shorter distances — 5Ks, 10Ks, and half marathons — using them as training checkpoints as much as goals in themselves.
I am not a running coach. I do not have any credentials in exercise physiology, sports science, or medicine. I’m a developer who runs, and who reads the papers behind the formulas used in the tools that runners use every day. That framing matters — it shapes everything about what this site is and isn’t.
Why this site exists
I got frustrated. Every running calculator I used gave me an answer without telling me where it came from. My GPS watch predicted a 3:45 marathon; Garmin Connect said something different; a random calculator on another site said something else. When I tried to understand why they disagreed, I hit walls of jargon and marketing copy with no actual sources.
So I went to the original papers. Jack Daniels’ 1979 work with Jimmy Gilbert on VDOT and the physiological analysis of marathon performance. Martti Karvonen’s 1957 paper on heart rate training zones. Robert Riegel’s 1981 analysis of race time prediction. The ACSM Compendium of Physical Activities. These papers are not hard to find, but they’re rarely cited on running sites — most tools are just copies of copies, and the provenance gets lost.
RunPaceLab is my attempt to build a different kind of running tool: calculators where the formula is shown, the source is cited, the limitations are stated plainly, and the math can be checked. A runner who wants to know why the numbers are what they are should be able to find out.
What this site is — and what it isn’t
RunPaceLab is a reference site for running performance formulas. It contains:
- Calculators that implement published formulas from primary sources
- Long-form articles explaining the science and math behind those formulas
- A glossary of running science and physiology terms
- Analysis of where formulas work and where they break down
RunPaceLab is not:
- A training advice site. I do not prescribe training plans, periodisation, or workout schedules.
- A coaching service. I am not qualified to coach runners.
- A medical resource. Nothing on this site is medical advice. Runners with health concerns should consult a doctor.
- A general fitness blog. The scope is deliberately narrow: the math and science behind running performance numbers.
When I write about, say, heart rate zones, I’m explaining what the Karvonen formula does and where it comes from — not telling you how to structure your training week. That distinction matters.
My running background
I started running in 2023, initially as a way to manage stress and get out of the house. The first few months were the usual story: starting too fast, getting injured, taking time off, starting again more carefully. I built up through couch-to-5K, then to 10Ks, then to a half marathon. The full marathon came about a year in, a decision made after a particularly strong half-marathon performance that suggested the fitness was there.
My training is unsophisticated by elite standards. I run by feel and pace, I use a GPS watch, and I track data in a spreadsheet. I’ve experimented with heart rate training, VDOT-based pace zones, and different long run structures, which is partly how I came to understand those tools well enough to implement and explain them. I train in Bengaluru’s heat and humidity, which is its own adventure in pace adjustment.
My marathon PR is the only marathon I’ve run, which technically makes it both my PR and my worst ever time. I’m hoping to change that in the coming cycle. I use the VDOT calculator on this site to track my fitness progression from race to race, which is exactly the use case it was designed for.
Editorial approach
Articles on RunPaceLab are researched from primary sources — the original papers, textbooks, and data. I use AI assistance (specifically Claude) to draft initial article structures and help with writing, then edit every article myself, checking the claims against the sources. Formula implementations are written and unit-tested by me. I do not have a physiologist review my work, because I don’t pretend that this site has expert editorial oversight that it doesn’t actually have.
What I do promise:
- Every quantitative claim that isn’t common knowledge has a citation to a primary source.
- Every formula is implemented from the original paper, not from a copy of another website.
- Limitations of formulas are stated plainly, not hidden.
- If I get something wrong, I want to know. Email me.
Contact
Email: udbstudios@gmail.com
I try to respond within a few days. I welcome corrections, questions about the formulas, and suggestions for new calculators or guides. I do not accept paid placements, sponsored content, or link insertions.
For privacy-related enquiries and data subject requests, use the same email address. See the Privacy Policy for details.