Weighted Sit-Up
abs
What moves the load, and what it costs
8.0MET
Abs is the prime mover, with the hip flexors assisting. The simplest way to make sit-ups a strength exercise rather than an endurance one.
Cue: Hold a plate across the chest, or overhead for more difficulty, and keep the movement smooth.
SOURCE·2024 Adult Compendium of Physical Activities·കാലിസ്തെനിക്സ്, കഠിനം എന്നതിന് കീഴിൽ·REVIEWED JUL 2026
SHARED AXIS · SEVEN VALUES FROM ONE TABLE · HIGHLIGHTED ROW IS THIS MOVEMENT
The compendium files weighted sit-up under a category, not a lift. Read the ladder as position, not precision: this is heavier work than sitting quietly by a factor of 8.0, and at the top end of what a gym floor produces.
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 weighted sit-up is filed under കാലിസ്തെനിക്സ് (ഉദാ. പുഷ്-അപ്പ്, സിറ്റ്-അപ്പ്, പുൾ-അപ്പ്), കഠിനമായ അധ്വാനം.
- Take the category's MET value — 8.0. One MET is the cost of sitting quietly, so this is 8.0 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 Weighted Sit-Up: 8.0 × 3.5 × 70 ÷ 200 = 9.80 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. |
| Hip flexorsIliopsoas and rectus femoris | Synergist / stabiliser | Lift the thigh towards the chest. They drive every leg raise and knee raise, which is why 'ab' exercises often feel like hip work. |
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, Weight plate. Every rep should look like the first one. The moment it stops looking like the first one, the set is finished.
PATTERN · BRACE
- Lie back with the knees bent and the feet flat, anchored only if the version calls for it.
- Cross the arms on the chest or reach them forward.
- Hold a plate across the chest, or overhead for more difficulty, and keep the movement smooth.
- Curl up one vertebra at a time, leading with the ribs rather than the head.
- Sit up until the torso is roughly vertical, then lower with the same control.
- Keep the movement smooth — no throwing the arms for momentum.
Where this one breaks down
Not theory. These are the faults you correct on a gym floor, and the correction that actually works.
Throwing the arms and head to generate momentum.
It converts the exercise into a hip flexor swing and a sore neck.
Anchoring the feet by default.
Anchored feet let the hip flexors do more of the work. Unanchored is harder on the abs and usually the better choice.
Crashing back down.
Lower under control; the lowering half is worth as much as the lifting half.
Regress it, or progress it
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 single-joint movement does its best work in moderate to high reps — very low reps load the joint before the muscle.
| Goal | Sets | Reps | Rest | Notes |
|---|---|---|---|---|
| Strength | 3–4 | 6–10 | 2 min | Single-joint work responds poorly to very low reps — the joint gets the load before the muscle does. |
| Muscle size | 3–4 | 10–15 | 60–90 sec | This is where isolation work earns its place: cheap volume for one muscle, little systemic fatigue. |
| Endurance / fat loss | 2–3 | 15–25 | 30–45 sec | High reps here are genuinely useful — the load is small enough that form survives the fatigue. |
| First month | 2 | 12–15 | 60 sec | Light. Isolation work is for adding volume later, not for building a base. |
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: കാലിസ്തെനിക്സ് (ഉദാ. പുഷ്-അപ്പ്, സിറ്റ്-അപ്പ്, പുൾ-അപ്പ്), കഠിനമായ അധ്വാനം — 8.0 MET. That is the published category this movement is filed under, not a measurement of this specific lift.
Worked at 8.0 MET × 3.5 × 70 kg ÷ 200 = 9.80 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.
Nothing at all to hand: V-Up is the closest match — same prime mover, same pattern, no kit.
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 weighted sit-up work?
Weighted Sit-Up is a single-joint isolation movement in which the abs is the prime mover, assisted by the hip flexors. Bends the trunk forward and, more usefully, resists it being extended backwards. Both a crunch and a plank load it — differently.
Is the weighted sit-up good for beginners?
Not on day one, but it is reachable within a few weeks. It rates 3 out of 5 for technical demand. Work up through the easier versions listed on this page first, starting with the sit-up.
What can I do instead of the weighted sit-up at home?
The closest no-equipment substitute is the v-up, which trains the same prime mover through the same movement pattern. If you own a little equipment, the decline sit-up is closer still. It will not load you as heavily, so use higher reps and slower tempo to make up the difference.
How many sets and reps of the weighted sit-up should I do?
For muscle size, 3–4 sets of 10–15 with 60–90 sec rest. For strength, 3–4 sets of 6–10 with 2 min rest. In your first month, 2 sets of 12–15, 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 weighted sit-up 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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