Leg Extension
குவாட்ரிசெப்ஸ்
What moves the load, and what it costs
3.5MET
Quadriceps is the prime mover. The only common exercise that isolates the quadriceps completely. It is neither the knee-destroyer nor the rehab miracle it gets called — it is a useful isolation movement.
Cue: Line the knee joint up with the machine's pivot and pause for a beat at full extension.
ஆதாரம்·2024 பெரியவர்களுக்கான உடற்செயல்பாடுகளின் தொகுப்பு·FILED UNDER WEIGHTS, 8–15 REPS·மறுபரிசீலனை ஜூலை 2026
SHARED AXIS · SEVEN VALUES FROM ONE TABLE · HIGHLIGHTED ROW IS THIS MOVEMENT
The compendium files leg extension 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 leg extension is filed under Resistance training (weight lifting), multiple exercises, 8–15 repetitions at varied resistance.
- 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 Leg Extension: 3.5 × 3.5 × 70 ÷ 200 = 4.29 kcal/min
ஆதாரம்·ACSM metabolic equation + 2024 Adult Compendium of Physical Activities·REFERENCE BODY MASS 70 KG·மறுபரிசீலனை ஜூலை 2026
What is actually doing the work
| Muscle | Role | What it does here |
|---|---|---|
| QuadricepsRectus femoris and the three vasti | Prime mover | Straightens the knee. Rectus femoris also crosses the hip and flexes it, so it is loaded differently in a squat than in a leg extension. |
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
Machine. Every rep should look like the first one. The moment it stops looking like the first one, the set is finished.
PATTERN · ISOLATION
- Set the seat so the knee joint lines up with the machine's pivot and the pad sits on the lower shin, not the ankle bone.
- Sit back into the pad and hold the handles.
- Line the knee joint up with the machine's pivot and pause for a beat at full extension.
- Straighten the knees smoothly until the legs are fully extended.
- Pause for a beat at the top with the quads squeezed.
- Lower under control through the full range.
Where this one breaks down
Not theory. These are the faults you correct on a gym floor, and the correction that actually works.
Slamming into full extension.
Smooth is what keeps this comfortable. Extend under control, hold, then lower.
Using the hands and hips to swing the weight.
If the backside lifts off the seat, the weight is too heavy.
Treating it as a knee-strengthening cure-all or as inherently dangerous.
Neither is true. It is a quadriceps isolation exercise, and a good one, used with sensible load and range.
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
This sits at the top of its progression here. Add load, add range, slow the tempo or go single-limb before you go looking for a new exercise.
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 | ஓய்வு | Notes |
|---|---|---|---|---|
| Strength | 3–4 | 6–10 | 2 நிமிடம் | 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 வினாடி | 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 வினாடி | 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: Resistance training (weight lifting), multiple exercises, 8–15 repetitions at varied resistance — 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.
ஆதாரம்·2024 பெரியவர்களுக்கான உடற்செயல்பாடுகளின் தொகுப்பு·CATEGORY VALUE, NOT A PER-EXERCISE MEASUREMENT·மறுபரிசீலனை ஜூலை 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: Bodyweight Squat 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 leg extension work?
Leg Extension is a single-joint isolation movement in which the quadriceps is the prime mover. Straightens the knee. Rectus femoris also crosses the hip and flexes it, so it is loaded differently in a squat than in a leg extension.
Is the leg extension good for beginners?
ஆம். இந்தத் தளத்தில் தொழில்நுட்பச் சிரமத்திற்கு இதற்கு 5 இல் 1 மதிப்பீடு — பயிற்சியாளர் இல்லாமல் ஒரே அமர்வில் கற்றுக்கொள்ளக்கூடியது. மிகக் குறைந்த நியாயமான சுமையுடனும், 12–15 என இரண்டு அல்லது மூன்று செட்களுடனும் தொடங்குங்கள்.
What can I do instead of the leg extension at home?
The closest no-equipment substitute is the bodyweight squat, which trains the same prime mover through the same movement pattern. If you own a little equipment, the resistance band leg extension 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 leg extension 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 leg extension burn fat from the quadriceps?
No. No exercise removes fat from the area it trains — spot reduction has been tested repeatedly and does not happen. Training the quadriceps 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 ஆதாரங்கள் 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.
ஆதாரம்·வெளியிடப்பட்ட உடற்பயிற்சிக் குறிப்புகள்·MUSCLE ROLES ASSIGNED BY JOINT ACTION·மறுபரிசீலனை ஜூலை 2026
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