Compound vs. Isolation: Squats, Lunges, and Leg Curls
Why multi-joint and single-joint lower-body exercises both have a place in a program.
Before this: The Thighs: An Overview
You will be able to
- Distinguish compound (multi-joint) from isolation (single-joint) lower-body exercises.
- Match the squat, lunge, leg extension, and leg curl to the joints and muscles they primarily train.
- Explain a benefit of including isolation work alongside compound lifts.
Compound: squat and lunge
The squat and lunge move at both the hip and knee joints at once, training the quadriceps, glutes, hamstrings, and adductors together. These compound movements are efficient and closely mimic real-world movement (sitting, standing, climbing).
Isolation: leg extension and leg curl
The leg extension (knee only, quadriceps) and leg curl (knee only, hamstrings) isolate a single muscle group at a single joint. They are useful for targeting a specific muscle, building it up as an accessory to compound lifts, or addressing a side-to-side strength imbalance that's hard to feel in a compound movement.
Why use both
A well-rounded program often uses compound lifts as the foundation and isolation exercises to fill in gaps — for example, adding leg curls if hamstring strength lags noticeably behind quad strength.
Sources for this lesson
“The quadriceps femoris and hamstrings can be trained through both multi-joint (squat, lunge) and single-joint (leg extension, leg curl) exercises.”
Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.6 Appendicular Muscles of the Pelvic Girdle and Lower Limbs
Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19
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