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Leg Curl
Positions & Range of Motion
- Start
- prone on a leg-curl machine (or seated variation), hips and pelvis pressed into the pad, knees near full extension, padded lever resting just above the heels/Achilles, ankles relaxed/lightly dorsiflexed
- End
- knees flexed with heels curled toward the buttocks through available range, hips still anchored to the pad, brief pause at end range
- Range of Motion
- ~0° to end-range knee flexion (up to ~90–120°), controlled return to near-full extension
How to Perform
A single-joint knee-flexion exercise that isolates the hamstrings, performed on a machine (prone/lying or seated) or with a band/ankle weight. Set up so the movement axis of the machine aligns with the knee joint and the padded lever rests just above the heels/Achilles. Keeping the hips and pelvis pressed into the pad (avoid arching the low back or letting the hips rise), curl the heels toward the buttocks by flexing the knees through the available range. Pause briefly at end range, then lower under control back to near-full knee extension. Keep the ankles relaxed or lightly dorsiflexed and the toes neutral; breathe out on the curl and in on the return.
Opens a YouTube search for “Leg Curl”
Coaching Cues
- 1
Press your hips and pelvis into the pad the whole time — the low back should not arch as you curl.
(stability) - 2
Drive your heels toward your glutes, then lower slowly and under control rather than letting the weight drop.
(tempo) - 3
Keep the ankles relaxed and toes neutral so you flex from the knees, not by cramping the calves.
(technique) - 4
Match effort on both legs; watch for one heel curling faster or higher than the other.
(symmetry)
Evidence-Based Dosing & EMG Data
General resistance-training guidelines apply: for hypertrophy/general strength, 2-4 sets of 8-15 reps, 2-3 sessions per week with progressive overload and roughly 1-2 minutes rest between sets. No leg-curl-specific dosing protocol is established.
Surface-EMG studies of the leg curl consistently show high hamstring activation with position-dependent differences. Hip position shifts the emphasis: the seated (hip-flexed) leg curl tends to elicit greater overall hamstring EMG — particularly of the biarticular heads (biceps femoris long head, semitendinosus, semimembranosus) — because the hamstrings are placed on greater stretch, whereas the prone (hip-extended) curl still recruits the uniarticular biceps femoris short head robustly. Medial (semitendinosus/semimembranosus) versus lateral (biceps femoris) balance can be biased by tibial/foot rotation, and the gastrocnemius contributes as a secondary knee flexor. Reported magnitudes vary widely across studies and setups, so these are qualitative trends rather than fixed percentages.
Muscles Involved (13)
Primary Movers
Stabilizers
Lengthened / Stretched
Synergists & Assistors
Easier Variations ↓
Band or ankle-weight leg curl
Perform the same knee-flexion motion prone or standing against a light resistance band or ankle weight, reducing load so full control is maintained.
Partial-range / lighter-load machine curl
Use a lighter machine load and work through a comfortable mid-range, gradually extending range and load as strength and tolerance improve.
Harder Variations ↑
Eccentric-emphasis / slow-tempo curl
Lift with both legs (or normally) and lower on one leg or over a 3-5 second eccentric to increase hamstring tension and eccentric strength.
Single-leg leg curl
Perform the curl one leg at a time to expose and correct side-to-side strength asymmetries and increase relative load.
Target Movements (1)
Why This Exercise Matters
Everyday activities this exercise helps you do — essential means it directly trains the capacity the task needs:
Goals This Helps With
Rehab, performance, prevention, and mobility goals this exercise supports — essential means it's a cornerstone:
Research Notes
claude-researched 2026-07; muscle/movement links validated against the roster. Adversarial clinical verification pending — do not promote past needs_review without human review.