Glossary

Plain-English definitions for the workout terms used throughout Datum and this guide. If a screen uses a word you don't recognize, it's probably here.

Set / rep#

A rep (repetition) is one complete movement of an exercise — one push-up, one bicep curl. A set is a group of reps done back-to-back without stopping — "3 sets of 8 reps" means you do 8 reps, rest, do 8 more, rest, do 8 more.

Activity#

A duration-based gym class or cardio-machine session (yoga, spin, treadmill, elliptical) — logged with a start/stop timer or after the fact instead of sets and reps. Can stand alone as its own workout or sit inside a strength session (e.g. a treadmill warm-up before lifting). See Classes & Cardio Activities.

Time-based exercise#

An exercise measured by duration instead of reps — a plank, a farmer's carry, a wall sit, or any other hold. Set on the exercise itself (in its detail screen, for a custom exercise), not per template, so an exercise is always either reps-based or time-based everywhere it's used. Logged with a live Start/Stop hold timer instead of a reps field, shown as minutes:seconds throughout the app, and tracked in Reports as a "longest hold" record instead of a weight PR, 1RM, or volume.

Compound / isolation exercise#

A compound exercise moves more than one joint and trains several muscle groups at once — a squat, a bench press, a row, a pull-up. An isolation exercise moves one joint and targets a single muscle group — a bicep curl, a leg extension, a calf raise.

Neither is better; they do different jobs. Compounds give you the most training for the time spent, which is why Datum leans toward them when you tell the plan builder you only have a short session. Isolation work is how you give a specific muscle attention it wouldn't otherwise get.

Working set#

A regular set done at your actual training weight — as opposed to a warm-up set or a drop set (below). When a template says "3 sets," it means 3 working sets.

Warm-up set#

A lighter, practice set done before your working sets to prepare your muscles and joints — for example, a few reps with just the bar before you load it up to your real working weight. Datum labels these W1, W2, etc. during logging. Warm-ups are excluded from your personal records, estimated 1RM, volume, and longest-hold records — they're not meant to represent effort at your real weight.

Drop set#

A technique where, immediately after finishing your last working set, you reduce ("drop") the weight and keep going for another set with no rest — a way to push a muscle past normal failure. Datum labels these D1, D2, etc. Unlike warm-ups, drop sets are counted toward your personal records, 1RM, and volume, since they're still real working effort.

Superset#

Two or more exercises done back-to-back with no rest in between, resting only after finishing a full round of all of them. For example, pairing bicep curls with tricep extensions and alternating between them set-for-set. Datum shows your progress through one as "Superset 1 of 2."

RPE (Rate of Perceived Exertion)#

A 1–10 scale (in half-point steps in Datum) for how hard a set felt, independent of the actual weight or reps. A 10 means you couldn't have done another rep; a 7 means you probably had 2–3 more reps left in the tank. It's entirely optional to log — useful if you want to track how hard your training feels over time, not just what weight is on the bar.

1RM (one-rep max) / estimated 1RM#

The most weight you could lift for a single rep of an exercise. Actually testing this is risky and inconvenient, so Datum estimates it from a normal set (e.g., a set of 20 lb × 12 reps implies a higher one-rep max than 20 lb) using a standard formula. It's an estimate, not a measured fact — useful for tracking whether you're getting stronger over time.

PR (personal record)#

Your best-ever result for a given exercise. Datum tracks best weight and best estimated 1RM separately — they don't have to come from the same session.

Volume#

Total work done for a muscle group, typically weight × reps summed across sets. Datum's "Volume by muscle group" chart in Reports uses this to show where your training effort is going.

Plate calculator#

A tool that tells you which weight plates to load on each side of a barbell to hit a target total weight, given the bar's own weight. See Logging a Workout.

Lean Body Mass#

Your body weight minus fat mass — everything else (muscle, bone, water, organs). This matches Apple Health's own leanBodyMass measurement type, so the two stay compatible if you sync them.

Split#

How you divide your training across the week — which muscles you work on which days. "Full Body," "Upper/Lower" and "Push/Pull/Legs" are all splits. See Training Approaches for the common ones, who each tends to suit, and their trade-offs.

Template vs. Plan#

A Plan is a folder that holds one or more Templates. A Template is one specific, reusable workout (its exercises and targets). See Plans & Templates.

Freeform workout#

A workout you start without a template, picking exercises as you go rather than following a pre-built plan.