A lifter walks into the gym feeling like garbage. Slept 5 hours. Big meal an hour ago. They’re sure today’s a “go through the motions” session.
First working set: PR.
Another lifter walks in feeling great. Caffeinated, mentally sharp, motivated. First working set: same load they hit clean two weeks ago, today it grinds. Second set, slower. Third, ugly.
Subjective readiness is a coin flip. The body knows things the brain doesn’t.
What today’s decision actually is
In tensr, four numbers come together as the “is today a hard day?” view:
| Metric | What it tells you |
|---|---|
| Readiness indicator | Today’s RFD on a baseline pull vs the trailing 4-session average |
| PR alerts | Any new all-time max in any tracked metric — not just weight |
| Session vs same-day-last-week | Today’s working-set quality vs the same movement, same day, last week |
| Session vs personal best | Today’s effort as a % of the all-time best for the same movement |
These aren’t four separate readings. They’re four windows on one question: should you push today, or back off?
Why it matters
Every athlete has had the experience of misreading themselves. The “I feel terrible” PR. The “I feel great” grind. The cumulative effect is bigger than the anecdote — programs based on subjective RPE drift over weeks, because RPE is calibrated against the lifter’s mood as much as their actual capacity.
A force-trace baseline taken in the first 60 seconds of a session — a max-effort isometric pull, recorded — predicts the next 60 minutes of work better than how the lifter feels. The force comes online or it doesn’t.
Two specific decisions this changes.
Which day is the hard day. A program with three lifting days a week often has one “main lift” target session and two supporting sessions. If the readiness number on Monday says today’s RFD is 12% below the trailing average, the right call is to swap Monday’s heavy work to Wednesday — when the data may be different — and move the supporting work to Monday.
When to stop pushing a session. If the readiness number was good but session vs same-day-last-week is showing a 15% decline two sets in, the body is telling you that the trajectory of this session is downward. Cap it early. Live to lift another day.
What to track together
The daily-decision triplet is best as one front-page-of-the-app view, not four separate dashboard cards.
| Combination | What it suggests |
|---|---|
| Readiness ↑, vs-last-week ↑ | Push. Try a PR. |
| Readiness ↑, vs-last-week ↓ | Something specific is off about this movement today. Switch it. |
| Readiness ↓, vs-last-week ↑ | Body is in the gym, brain isn’t. Run the session, don’t reach. |
| Readiness ↓, vs-last-week ↓ | Deload day. Take it. |
PR alerts are passive — they pop up when a metric exceeds its all-time best. They’re satisfying and useful for trend confidence, but they’re not the active decision input. The active inputs are the comparison numbers.
What gear it needs
Mixed by metric:
- Readiness via RFD wants 80 Hz. The baseline pull’s slope is what carries the signal; at 8 Hz the slope is too noisy to be informative.
- PR tracking on TUT, impulse, peak force, set TUT is honest at every sample rate.
- Session vs same-day-last-week is honest everywhere when the comparison metric is impulse or TUT.
For lifters on a $30 sensor: the PR alerts and same-day-last-week comparisons still work. The RFD-based readiness signal doesn’t, but session vs last-week is a fair substitute for “is today drifting up or down.”
What to do tomorrow
The simplest possible test:
- First minute of your session, before any working sets: a single max-effort isometric pull on a movement you do regularly. Five seconds, maximum tension, recorded.
- Look at the peak force.
- Compare to the average of the last four sessions’ baseline peaks.
Within ±5% of the average: today is a normal day. Run the program.
5–10% below: today is a maintenance day. Run the program but don’t reach for PRs; cap intensity at planned levels.
10%+ below: today is a deload day or a recovery day. Switch the session, or do mobility work, or go home.
A specific framing: this isn’t a global wellness metric. It’s a same-task, same-conditions baseline. The number doesn’t tell you anything about your sleep or mood — it tells you what your nervous system can produce in the gym, on this exercise, today. That’s a narrower question than “am I well?” and it’s the one that matters for the next 60 minutes.
The body knew already. The number says it out loud.