Plank
abs
What moves the load, and what it costs
3.5MET
Abs is the prime mover, with the obliques, front deltoid, glutes assisting. The default trunk exercise and a good one, as long as it is held properly and not for five minutes. Once a minute is comfortable, make it harder rather than longer.
Cue: Tuck the pelvis under and squeeze the glutes — a plank held with an arched back trains almost nothing.
Written on other cards as: Front plank · Forearm plank
SOURCE·2024 Adult Compendium of Physical Activities·FILED UNDER CALISTHENICS, LIGHT·REVIEWED JUL 2026
SHARED AXIS · SEVEN VALUES FROM ONE TABLE · HIGHLIGHTED ROW IS THIS MOVEMENT
The compendium files plank under a category, not a lift. Read the ladder as position, not precision: this is heavier work than sitting quietly by a factor of 3.5, and middling for conditioning work.
Turning that MET value into a real energy cost
- Map the movement to a published category. The compendium measures categories of conditioning work, never individual lifts, so plank is filed under Calisthenics, light or moderate effort, general (e.g. back exercises).
- Take the category's MET value — 3.5. One MET is the cost of sitting quietly, so this is 3.5 times resting metabolism.
- Multiply by 3.5 to get millilitres of oxygen per kilogram per minute, the unit the MET is actually defined in.
- Multiply by your bodyweight in kilograms and divide by 200. The result is kilocalories per minute of work.
- Count working minutes only. Under load, not under the roof — a set of eight is about 25 seconds of the hour you were there.
kcal/min = MET × 3.5 × body mass (kg) ÷ 200 Plank: 3.5 × 3.5 × 70 ÷ 200 = 4.29 kcal/min
SOURCE·ACSM metabolic equation + 2024 Adult Compendium of Physical Activities·REFERENCE BODY MASS 70 KG·REVIEWED JUL 2026
What is actually doing the work
| Muscle | Role | What it does here |
|---|---|---|
| AbsRectus abdominis | Prime mover | Bends the trunk forward and, more usefully, resists it being extended backwards. Both a crunch and a plank load it — differently. |
| ObliquesExternal and internal obliques | Synergist / stabiliser | Rotate and side-bend the trunk, and resist rotation. The internal oblique on one side works with the external oblique on the other. |
| Front deltoidAnterior deltoid | Synergist / stabiliser | Raises the arm to the front (shoulder flexion) and assists horizontal adduction. Prime mover in overhead pressing, heavy synergist in every bench press. |
| GlutesGluteus maximus, medius and minimus | Synergist / stabiliser | Extends the hip (maximus), and abducts and stabilises it (medius and minimus). The strongest single muscle group in the body. |
The prime mover produces the movement against the resistance; synergists assist and stabilisers hold a joint still without moving it. An exercise trains the whole muscle it loads — there is no way to work only part of a muscle, and no exercise removes fat from the area around it.
Set up, then earn the rep
Bodyweight. Held for time, not counted in reps — the set ends when the position breaks, not when the clock does.
PATTERN · BRACE
- Set the elbows under the shoulders (or the hands, for a straight-arm version) and the feet at hip width.
- Push the floor away so the upper back is slightly rounded rather than sagging between the shoulder blades.
- Tuck the pelvis under and squeeze the glutes — a plank held with an arched back trains almost nothing.
- Tuck the pelvis under, squeeze the glutes and pull the ribs down — the lower back should feel flat, not arched.
- Hold, breathing normally, with the neck in line with the spine.
- End the set when the position changes, not when a target time is reached.
Where this one breaks down
Not theory. These are the faults you correct on a gym floor, and the correction that actually works.
Hips sagging.
A sagging plank loads the lower back and trains nothing. Squeeze the glutes and drop to the knees if that is what it takes.
Backside in the air.
Piking makes the hold easy and pointless. Straight line from ear to ankle.
Chasing five-minute holds.
Past about a minute you are training patience, not the trunk. Add load, lengthen the lever or make it single-limb instead.
Regress it, or progress it
Regress — earn it first
Nothing on this site regresses it further: this is already near the entry point of its pattern. Take load off, shorten the range, or slow the tempo — in that order.
Progress — the next demand
Prescription: load, reps, rest
Read off the goal, then hold the technique constant as the load climbs. Derived from the movement's mechanics, not invented for this page: a held position is measured in seconds, and the set ends when the position breaks.
| Goal | Sets | Hold | Rest | Notes |
|---|---|---|---|---|
| Learning the position | 2–3 | 15–20 sec | 45–60 sec | Stop the set when the position breaks, not when the timer does. |
| Building capacity | 3–4 | 30–45 sec | 60 sec | Add time before you add load, up to about a minute per set. |
| Strength (loaded) | 3–4 | 20–30 sec | 90 sec | Past a minute of easy holding, add resistance rather than more seconds. |
| Fat loss / circuits | 3–4 | 30–40 sec | 20–30 sec | Short rests keep the heart rate up; the position still has to hold. |
Time under load, in kilocalories
Read these as minutes of work, not minutes in the building. A set of eight takes about twenty-five seconds; the rest of the hour is rest, chalk and queueing.
Mapped category: Calisthenics, light or moderate effort, general (e.g. back exercises) — 3.5 MET. That is the published category this movement is filed under, not a measurement of this specific lift.
Worked at 3.5 MET × 3.5 × 70 kg ÷ 200 = 4.29 kcal per working minute for a 70 kg adult. Scale it by your own bodyweight; the equation is linear. The full activity dataset lives at BurnLab.
SOURCE·2024 Adult Compendium of Physical Activities·CATEGORY VALUE, NOT A PER-EXERCISE MEASUREMENT·REVIEWED JUL 2026
If the rack is taken
Substitutes train the same prime mover through the same pattern with different kit. Computed from the muscle and pattern data on this card, not hand-picked to fill a grid.
This one needs no equipment at all, which is why it belongs in every travel and home programme. Every no-equipment movement is listed together.
Where it sits in a week
One movement is not a programme. The twelve templates put these in order, including 6 that need no gym at all.
The questions that come up on the floor
What muscles does the plank work?
Plank is an isometric hold in which the abs is the prime mover, assisted by the obliques, front deltoid, glutes. Bends the trunk forward and, more usefully, resists it being extended backwards. Both a crunch and a plank load it — differently.
Is the plank good for beginners?
Yes. It rates 1 out of 5 for technical difficulty on this site — learnable in a single session with no coaching. Start with the lightest sensible load and two or three sets of 30–40 sec.
What can I do instead of the plank at home?
Nothing is needed — the plank already requires no equipment at all, which is why it belongs in any home programme.
How many sets and reps of the plank should I do?
For muscle size, 3–4 sets of 30–45 sec with 60 sec rest. For strength, 2–3 sets of 15–20 sec with 45–60 sec rest. In your first month, 3–4 sets of 30–40 sec, stopping well short of failure. Total weekly hard sets per muscle group matters more than the exact rep number in any of these ranges.
Does the plank burn fat from the abs?
No. No exercise removes fat from the area it trains — spot reduction has been tested repeatedly and does not happen. Training the abs builds the muscle underneath; where body fat is lost from is decided by an overall calorie deficit and by your genetics, not by which exercise you chose.
Muscle roles follow standard kinesiology references and are described by joint action rather than by gym convention — see how this site is built. Energy figures are derived from the 2024 Adult Compendium of Physical Activities. Every reference is named and dated on the sources page. General information only — not medical or coaching advice. Load, form and progression should be adjusted to your own experience and any injury history. When in doubt, get coached in person.
SOURCE·Published exercise references·MUSCLE ROLES ASSIGNED BY JOINT ACTION·REVIEWED JUL 2026
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