Sandbag Lunge · Front Knee Flexion at Depth

Why this matters

The front knee flexion sets the depth of the lunge. About 90° is the sweet spot: deep enough that the trailing knee can reach the ground (the movement standard), but not so deep that the front knee shoots well past the toes and loads the patellar tendon.

What good looks like

• Front knee bent to roughly 90° at the bottom.
• Trailing knee able to reach the floor from this depth.
• Front knee tracking over (not far past) the toes.

Common faults

Too Shallow (> 110°)

Not enough bend. The trailing knee can't reach the ground, so the rep risks a no-rep.

Causes: rushing, fatigue, or trying to stay tall to move faster.

Effect: no-rep risk, short stroke.

Over-Bent (< 75°)

The front knee is driven well past the toes. Combined with a forward shin, this loads the patellar tendon.

Coaching cues

• "Knee to the floor" — ensures depth for the trailing-knee touch.
• "Bend to ninety" — names the target.

How to draw

1. Pause on the knee-touch frame.
2. First line: greater trochanter → lateral femoral condyle (thigh).
3. Second line: lateral femoral condyle → lateral malleolus (shank).
4. Interior angle at the knee is the reading.

Related measurements

• Front Shin Angle at Depth — measured from the same drawing as this knee flexion (one tool, two readings).
• Front Shin Angle at Depth — where the depth puts the load.