The squat is the most-screened movement in fitness
It tests ankle dorsiflexion, hip mobility, thoracic extension, core stability, and full-body coordination — in one movement. When a squat looks bad, you can diagnose which link broke.
The mechanics
A back squat is a triple-joint movement at ankle, knee, and hip. The barbell sits on the upper back, creating a load vector that runs straight down through the body. For the bar to stay over mid-foot (the balance point), the body must arrange itself so the center of mass is also over mid-foot.
This requires:
- Knees travel forward to maintain mid-foot bar path
- Hips travel back to counterbalance the knees
- Torso angle adjusts based on relative femur and torso lengths
Why squats look different on different bodies
Long femurs + short torso = more forward lean, more hip-dominant Short femurs + long torso = more upright, more knee-dominant
This is anatomy, not technique. A long-femur client will never squat as upright as a short-femur client. Trying to force them upright creates lower-back hyperextension or unloads the heels.
The 4 most common breakdowns
Knees cave (valgus) — usually weak glute medius or limited ankle dorsiflexion. Cue "knees out." Add lateral band work. Butt wink (lumbar flexion at bottom) — limited hip flexion ROM, often due to tight hamstrings or anteriorly tilted pelvis. Stop the rep above the wink. Address mobility outside the lift. Heels lift — limited ankle dorsiflexion. Use heel-elevated squats (1-2 inch wedge) until ankle mobility improves. Forward collapse (good morning squat) — weak quads, weak core, or bar position too high on the back. Strengthen the quads with front squats.Variations and what they emphasize
High-bar back squat — more upright torso, more quad-dominant Low-bar back squat — more forward lean, more posterior-chain (hip) Front squat — most upright, maximum quad and core demand Goblet squat — beginner-friendly, builds anti-flexion core strength Box squat — teaches sitting back, controls depth, builds posterior chainProgramming squats safely
- Most clients should learn goblet → front → back, in that order
- Depth is "as deep as good mechanics allow" — not arbitrary
- Add load only when mechanics hold across reps
- 1-3 hard squat sessions per week is plenty for most clients
TL;DR
The squat is a triple-joint movement that exposes ankle, hip, and core limitations. Body proportions determine torso angle — anatomy, not technique. Common faults trace to specific limitations: cave = ankle/glute, wink = hip ROM, heel lift = ankle, collapse = quads/core.