Questions, answered.

As a proponet of the open-web, and open-standards — we hope to support those browsers as soon as they offer the Bluetooth connections into the Browser. Chrome (and thus Edge) are often a first-mover for new connections. So those are what allowed this product to exist today.

Time under tension is a proxy for mechanical tension — the muscular signal that tells your body to adapt. A decade of hypertrophy research points consistently to mechanical tension sustained over time as the primary driver of muscle growth, more than peak load or rep count alone. Two lifters doing the same "3×10 at 100 lbs" can have wildly different TUT depending on tempo, rest, and range of motion — which means one of them did meaningfully more work than the other. Rep counts and weight on the stack don’t capture that. Force × time does. And for banded work, where the resistance varies as the band stretches, TUT (and better, impulse — the force-time integral) is the only honest way to progress session-over-session.

Maybe. What we do know is you CAN GET JACKED with tensr.fitness but YOU have to do the work. Sleep, diet, consistency, progressive overload, recovery — that’s all you. What tensr.fitness changes is that you stop guessing whether you actually trained harder than last week. The number is either bigger or it isn’t. When you are ready to change, most people want data that mirrors back to them — the you cold, hard, truth about your training session.

tensr.fitness is a play on words. Obviously "tension" in the weights and cable system, and but also large sets of numerical data can be called vectors or "tensors" — in fact if you ever hear about Google’s AI hardwware called "TPUs" the T stands for Tensor. Also tensr.fitness had to have the obligatory mis-spelling to find a solid domain name.

Yes we are considering that. It would be something that helps with session annotation (a unique funciton that existing sensors dont offer), and it would offer other design-features too. Have thoughts — drop us a line at sensors@tensr.cc.

Eric Moore is the founder and Product Owner. Avid fitness guy + and absolute data-nerd.

Sadly Not right now. tensr.fitness, for now, only works with inline tension where a sensor is clipped between an anchor and your hand. Barbells, dumbbells, pull-up bars, etc — have nowhere to put one. Right now we shines with: bands, cable machines, selectorized stacks, suspension trainers, and any anchored-resistance setup.

Recently there have been a flurry of incredble looking digital resistance excercise options. Products like the Beyond Power Voltra, the Tonal Smart Gym, Flex by Shogun, Ancore Pro, GoTone on Amazon, MaxPro, Freak Athlete Atom, AvantGo on Amazon, etc. and ideally NO the tensr.fitness app SHOULD not be needed if you are training with something that is CREATING the force — by definitiion — it COULD record what it is doing — and how much it resisted you and for how long. Does it? You tell us — I did not buy any of these products for 1 of at least 3 reasons.

1. Too Soft.
2. Too Expensive
3. Not-proven

Listen, we have been looking at the Voltra too! but as someone who already got their wife over the the decision to buy plate stacks. I can’t yet justify a Voltra. Furthermore if that thing died, my wife might kill me with the Voltra (I can already hear the doctors grumbling something about, "…blunt force trauma to the head").

1) Not strong enough: for regular gym-use — most gym-goers are cablable of leg work that hits at least 100lbs — so we find that products that cant reach 100lbs of resistance as just a rehab tool.

2) Longevity of Electromagnetic Drive: How long will my weigh stack be useful for training? Until I try hard to break them, until Jesus comes back (wont need them), or until the heat-death of earth (wont need them). So, for me, thats long enough. How long will the Electromagnetic Drive last in a Voltra? I hope for the sake of how cool it is — and for everyone else out there who has one — that is something like 10 years +. But until we get some resolution to that projection. I am just going to rest knowing my weights are good, and if I need a new sensor, cause a plate falls and cracks it to bits. No propblem.

3) Frowny Face Pricing: Prices that make my wife frown at me. nuf said.

We come from a by-gone era — where people made simple software. It was just you and your device. So while this is in the browser, it does not send any data out. In fact it even works offline. Everything you make is there on your device — never has to leave. Every force sample is stored in your browser on your device. If you never login — you never send anything to us. If you sign in on the Free tier, you can opt-in to sync workouts to tensr.fitness for cross-device access — but it stays opt-in and never required for the app to function.

In the 90s people want to own their data. With Records, CDs, Casettes, LaserDisc, etc. We thought that time was pretty rad. and want to have the same joy of keeping it simple. Your data — is, just that. It’s YOUR data. Always. And Forever. We store it in open standards — SQLite, NDJSON, CSV etc are options that you can use to get access to your data. That data and the formats are well-documented, open, and not-proprietary. If tensr.fitness ever goes-away, your training history keeps working with any tool that reads those formats.

Not really — they log what you planned (sets, reps, weights); tensr.fitness logs what actually happened at the muscle level. They’re complementary. Paid-tier users get imports from those trackers so the two sides of the picture can live in the same place.

No catch. The product is free because the open data and a real leaderboard are worth more to us than keeping some recording-features stored away in a tower like Rapunzel. So thanks for taking our little Rapunzel of the tower. Please take her to the gym. Show off some band work, do some lengthened partials, do bi-cep curls, get after it.

Anyway, paid tiers add convenience (long history, cross-exercise analytics, coaching credits, video) — they don’t unlock the core experience. When you find "your people" (people who bring a sensor to the gym — dont make them pay to stay :)

Soon.

The data formats and BLE wire protocols are open and documented. The sensor readers (@hangtime/grip-connect) is open-source under BSD-2-Clause. The app itself is currently closed-source; if that ever changes it’ll be a deliberate call, not an accident.