Notes on metrics, training, and honest measurement.
33 posts, in 9 collections. Ideas about what to measure and why it matters, plus workouts you can preview here and take into your own training log.
Change log
What changed in each release, how to try it, and where to send feedback. The home of the Tensr beta program.
- 02iPhone build 2020: a new default rep counterThe phone-motion demo and sensor-backed training now use the smoothed bathtub counter. Here’s what changed and what to try.
- 01Web release: choose your rep counterA detector strategy picker adds the filtered bathtub counter as Default, with Classic and raw bathtub available for comparison.
Workouts
A workout lookbook. Preview the plan, make it yours, and take the workout.md file with you.
- 38One cable session, in a file you can keepA portable cable workout with an interactive preview, source credit and a workout.md download.
- 39A cable A/B split you can inspect before importingA portable cable workout with an interactive preview, source credit and a workout.md download.
- 40Three cable days, with the provenance still attachedA portable cable workout with an interactive preview, source credit and a workout.md download.
The framework
The Tension In Making Each Second Count
- 01Time under tension, finally measured.Two lifters do '3×10 at 100 lbs.' One finishes in 90 seconds, one in 220. The integer in your set log can't see the difference. Time under tension can.
- 02Having the Impulse to Measure ThingsTim went 50 lbs; Thomas went 45. Tim popped it; Thomas held it. The bar weight says one of them lifted heavier — the math says the other one trained harder. Impulse is the area under the force–time curve, and it's the unit volume should have been measured in all along.
Not all reps are equal
Tempo, effective reps, fatigue. How your set log is hiding things from you.
- 03Slow the eccentric. Watch the number move.Same load, same reps, double the eccentric — the set TUT changes by 60% and the set looks identical on paper. Tempo is the biggest hypertrophy lever most lifters never measure.
- 04Only the hard reps grow you.A set of 12 where reps 1–7 are warm-ups for reps 8–12. The first seven are heating; the last five are stimulus. Effective reps put a number on which is which.
- 05Junk volume has a fingerprint.The set where rep 1 peaks at 400 N and rep 12 peaks at 240. The middle reps were the work. The last three were noise. Decay is not failure — it's the shape that names the load mistake.
Hard truths
Form quality, symmetry, RFD, and adherence.
- 06When reps stop looking the same.Two reps with the same peak force can look completely different in shape. The force–time curve is a fingerprint — and when the fingerprint changes mid-set, form is breaking down before the numbers say it has.
- 07The side you train less is bigger than you think.Asymmetry is invisible in a normal set log because bilateral movements get recorded as one number. With two sensors, it shows up immediately — and so does its trend.
- 08How fast can you get tight?Two athletes hit the same peak force. One in 180 ms, the other in 700. In a sport that ends in under a second, that's everything. Rate of force development, measured directly from the force–time curve.
- 09Discipline, on the timeline.A four-week tempo block on paper. At the end, the lifter doesn't know whether they actually hit the tempo or drifted week by week into whatever felt right. tensr closes the loop.
The long view
What you do with months of data.
- 10Your weekly volume in newton-seconds.'I added a set to back day this week' — how much more work was that, exactly? Weekly impulse rolled up by muscle group is the volume view your training plan actually wants. It survives switches between bands, cables, and stacks.
- 11Is today a hard day?The lifter who walks in feeling like garbage and PRs anyway. The one who feels great and grinds. Subjective readiness is a coin flip; a force-trace baseline in the first 60 seconds is not.
- 12Compared to whom?A 5-foot-3 lifter ranked on the same leaderboard as a 6-foot-4 lifter. Useful information density: zero. The right comparison is you, last month, on the same gear.
Tools and trust
Sensor honesty and data ownership.
- 13Your $30 scale is not lying. But it's not omniscient.Why a 1 Hz crane scale gives you a perfectly honest impulse reading and a wildly dishonest RFD reading. Sample rate is not a marketing detail; it's whether the metric is real or invented.
- 14Open data, closed care.Every fitness app you've used has had at least one moment where you wanted to leave and couldn't. The database in tensr is a SQLite file on your device. Cloud is opt-in. Exports are first-class. Your data is yours.
- 30Enshittification needs a hostage.Training is great. Training apps are great, sometimes. Then enshittification shows up, and leaving costs you the years you already logged. What fitness apps have taken away, and what we're building into tensr so the exit is real.
Building in Public
How Tensr is made, and why. The decisions, experiments, bugs, and real workouts behind the product.
- 01We built a QR fountain. Then we deleted the fountain.From fountain coding to repeating blocks, then portable documents: why airgapped QR transfer made a better demo than an everyday sharing workflow.
- 02The sensor was right. Our timestamps were wrong.A force-recording investigation found that Bluetooth arrival times were standing in for measurement times. Here is what that breaks and how we plan to separate the two clocks.
Head to head
Honest comparisons — including where the other thing is the better answer.
- 29Strong records what you told it.Strong is a capable workout logger. Tensr adds force recordings on compatible cable, band, and suspension movements. Here is where that difference matters, and where it does not.
- 30A notebook keeps the record and you do the sumsPaper is a capable training tool. The case for Tensr starts when you want to query the history or add a force recording, rather than replace a habit that works.
- 31Hevy brings your training partners with youHevy makes training social. Tensr's force layer addresses a different question: what evidence sits behind a shared result, and which comparisons the recording actually supports.
- 32Fitbod plans the workout from the evidence it hasWorkout recommendations and force recordings answer different questions. Fitbod's recovery model is useful context, while a measured trace still cannot diagnose fatigue.
- 33Boostcamp supplies a plan and Strength Level supplies a referenceA program, a population benchmark, and a force recording solve different problems. Here is how to use the distinction without dismissing the training log.
- 34Tonal makes the gym an applianceTonal combines resistance and coaching in one system. Tensr records compatible equipment you already use. The comparison starts with the training experience each tool supplies.
- 35Vitruvian changes the resistance while you liftThe Trainer+ combines a floor platform with adaptive resistance. A passive force sensor has a different role, and the distinction matters more than a contest over charts.
- 36Speediance puts the cable station in one systemA connected cable gym combines resistance, interface, and tracking. Tensr adds a recording layer to compatible equipment without supplying that integrated experience.
- 37Everyday is Bring your Tindeq to the Gym DayThe Progressor is useful hardware with its own app and an open Bluetooth interface. Tensr offers another recording workflow for compatible strength-training setups.
- 38VALD DynaMo and Tensr: two workflows for measured strengthVALD's DynaMo is a closer comparison than force plates: both workflows can involve measured tension. The difference is in the hardware, assessment tools, and role of the training record.
- 39Trust how the set felt and give it a referencePerceived effort and force recordings describe different parts of a set. The useful comparison keeps the athlete's judgment instead of treating a sensor as a substitute for it.