Notes on metrics, training, and honest measurement.
Fourteen posts, in five arcs. Each one is anchored to a cohesive block of metrics tensr can capture from the force–time curve of a single set — what to track, why it matters, and what to do about it tomorrow.
Arc A The framework
The Tension In Making Each Second Count
- 01 Time 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.
- 02 Having the Impulse to Measure Things Tim 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.
Arc B Not all reps are equal
Tempo, effective reps, fatigue. How your set log is hiding things from you.
- 03 Slow 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.
- 04 Only 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.
- 05 Junk 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.
Arc C The second wave
Form quality, symmetry, RFD, and adherence.
- 06 When 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.
- 07 The 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.
- 08 How 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.
- 09 Discipline, 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.
Arc D The long view
What you do with months of data.
- 10 Your 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.
- 11 Is 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.
- 12 Compared 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.
Arc E Tools and trust
Sensor honesty and data ownership.
- 13 Your $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.
- 14 Open 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.