Fysiqal
Safety
Safety

Locking Out — When It Is and Isn't Risky

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Historical reference: its only source is the original reference manual, and some of it may be out of date. Not used for AI answers until re-sourced.

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locking-outkneesquatleg-extensioncalvesjoints

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DefinitionA short reference note, not a full lesson.
Definition

Locking out joints under load is generally avoided in the squat and calf raises, but in the leg extension it is "not very dangerous" because the resistance pushes the shins down.

Detail

Locking out (fully extending a joint under load) is treated differently by exercise:

  • Squats: Do not lock out the knee.
  • Standing calf: Don't lock out the knees (and don't bend the knees to help with the movement).
  • Leg extension: Locking out is not very dangerous, because the resistance force is pushing the shins down.

The distinction is the direction of the resistance relative to the joint: when the load would drive a locked joint into hyperextension or bear straight down on it, locking out is avoided; when the load instead acts to keep the joint controlled, locking out is comparatively safe.

Key facts

  • Squats: do not lock out the knee.
  • Standing calf: do not lock out the knees.
  • Leg extension: locking out is not very dangerous (resistance pushes the shins down).

Connections

Sources

Historical reference · reference manual (page cited)
p.32p.504p.688
Pages: 32, 504, 688.

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Atlas Connections

Gastrocnemius
A 2-joint calf muscle that plantar-flexes the ankle and flexes the knee; origin at the femoral condyles, insertion at the calcaneus.
Knee Joint Range of Motion
The knee is a hinge joint that straightens to about 0° and, in healthy adults, bends to roughly 133–142° depending on age and sex (CDC reference data). The "90°" often quoted is the arc of a seated leg extension, not the knee's full range.
Soleus
A single-joint calf muscle that plantar-flexes the ankle; trained with seated calf raises.
Knee Safety in the SquatClosely related
Safe squatting protects the knee by not locking out, keeping proper spinal alignment, squatting as deep as your mobility allows with control, and managing patellar tracking — knee pressure jumps ~8× from standing to a 90° bend, which is why stopping at parallel isn't the low-stress option it seems.
Knee Safety in the Leg ExtensionClosely related
Because the knee is a hinge joint, the leg extension requires aligning the patella with the cam's axis of rotation and a slight inward rotation of the quads so extension stays in a vertical plane; locking out is not very dangerous here.