“I added a set to back day this week.”
How much more work was that, exactly? A set of bent rows at moderate band tension? A high-rep finisher at light load? A heavy single? “More” is not a number. Programming on “more” is programming by vibes.
What weekly volume in newton-seconds actually is
Every set produces a total impulse — the integral of force over time, in newton-seconds (N·s). Every session is a sum of sets. Every week is a sum of sessions. Every movement maps to muscle groups.
Roll all that up, and you get a volume view that survives equipment changes:
| Metric | What it aggregates |
|---|---|
| Weekly impulse / movement | All sets of one specific movement this week |
| Weekly impulse / muscle group | All movements that load that muscle group, mapped via primary/secondary |
| Weekly impulse / body side | Left vs right total, when the rollup data exists |
| Weekly TUT / muscle group | The seconds-loaded view, complementary to impulse |
| Weekly volume change | This week vs last week, in % |
| Weekly push:pull ratio | Push impulse over pull impulse |
| Block accumulation | Sum across weeks (default block = 4 weeks) |
| Block load progression | Linear fit of weekly impulse over the block |
These all derive from one underlying number: the integral of force on every set you recorded. The aggregations are pure arithmetic.
Why it matters
“Sets × reps × weight” only ever worked for the bar. The moment you switched to bands, cables, or selectorized stacks, the unit started to lie — same set log entry could represent dramatically different stimuli depending on starting tension, range, hand position. Most lifters’ weekly volume “totals” are estimates plus tradition.
Weekly impulse is denominated in the unit your body actually responds to. Three things it changes:
Equipment-agnostic comparisons. Bands today, cables next week, plate-loaded the week after. The N·s readout is the same arithmetic regardless of the source; you can swap movements for variety or hardware availability without losing the trend line.
Muscle-group-level honesty. The classic “back day” log might say “3 sets bent row, 3 sets pull-up, 3 sets face pull.” That’s a movement count. The N·s rollup says “8400 N·s on lats, 2100 N·s on rear delts.” When the lats stop progressing, you can see exactly how much of the dose is hitting them.
Real “added a set” arithmetic. If your average bent-row set is 1100 N·s, adding one set adds 1100 N·s to the week — a 13% bump if your back week was at 8400 N·s, a 40% bump if it was at 2750. Either decision now has a number behind it.
What to track together
The weekly/block view is one zoomed-out picture. Treat the metrics as concentric circles around the same data.
| Scope | What you’re answering |
|---|---|
| Weekly impulse / muscle group | Is each muscle group getting the dose I planned? |
| Weekly volume change | Is total work going up, holding, or drifting down? |
| Block accumulation | Across 4 weeks: is the volume target being met? |
| Block load progression | Is the trend within the block ascending? |
| Push:pull ratio | Are antagonist groups balanced or skewing? |
Pair total with trend. A weekly total of 12000 N·s on chest sounds fine until you see it’s been declining 8% per week for three weeks — at which point either the program intends to deload, or something is off.
What gear it needs
Honest at every supported sample rate. These metrics are aggregates of impulse, which itself is an integral — and integrals smooth out under-sampling. An 8 Hz crane scale gives you weekly volumes you can trust.
This is one of the metrics where a $30 sensor genuinely replaces a more expensive solution. If you only ever looked at weekly volume per muscle group, you’d never need to upgrade your hardware.
A specific note on rollups: tensr maps each movement to primary, secondary, and stabilizer muscles. The defaults are reasonable, but they’re judgment calls. A lat pulldown could weight latissimus 70%, biceps 20%, lower trap 10% — or different splits. The values are tunable per movement; the assumption should be visible to the lifter, not hidden inside the number.
What to do tomorrow
Skip a movement you usually do. Look at last week’s weekly impulse rolled up by muscle group. Now imagine that movement subtracted out.
For most lifters, this exposes one of two patterns:
- The movement contributed less than you thought. “I do bent rows every week” — and bent rows turn out to be 800 N·s of an 8000 N·s back week. They’re not load-bearing. Drop or replace freely.
- The movement was carrying the muscle group. “I do pull-ups every week” — and pull-ups turn out to be 5500 N·s of a 7500 N·s back week. Skip them, and back is undertrained for the week.
Either result changes how you think about substitutions. “More” is now a number. “Less” is too.
Bands, cables, plates, machines. Different equipment. Same unit. Real programming.