Sandbag Lunge · Front Shin Angle at Depth

Why this matters

The sandbag lunge is 100 m of unilateral endurance under an axial (top-down) load. Over that distance, joint stress accumulates — and the front shin angle decides where the load goes.

A vertical shin shifts the load back into the large gluteus maximus and hamstrings. A steep forward shin concentrates shear on the patellar tendon.

In general strength training, knees tracking slightly over the toes is fine. But repeated for 100 m under load, a steep shin is the fast-fatigue and overuse pattern on this station. Keeping the shin vertical lets the durable posterior chain carry the work.

What good looks like

• Front shin close to vertical at the bottom.
• Knee stacked roughly over the ankle, not driven past the toes.
• The athlete feels the load in the glute, not the knee.

Common faults

Steep Shin (> 22°)

The knee drives well past the toes. Patellar-tendon shear climbs with every rep; the quads burn out long before 100 m.

Causes: a short stride (the step lands too close), or a quad-dominant habit.

Effect: patellar shear, quad burnout, slowing pace.

Moderate Lean (12–22°)

Some forward shin — manageable for a while but trending toward the steep fault under fatigue.

Coaching cues

• "Step longer, shin tall" — lengthens the stride so the shin stays vertical.
• "Sit back into the glute" — biases load to the posterior chain.

How to draw

1. Pause on the frame the trailing knee contacts the ground.
2. First point: lateral malleolus (ankle) of the front leg.
3. Second point: lateral femoral condyle (knee) of the same leg.
4. The acute angle vs vertical is the reading.

Related measurements

• Front Knee Flexion at Depth — same frame; how deep the front knee bent.
• Trunk Angle at Depth — the upper-body half of the bottom position.