Sandbag Lunge · Trunk Angle at Depth

Why this matters

The sandbag sits high on the upper back, so it acts as a long lever on the spine. A small amount of forward trunk lean is good — it recruits the glutes to drive the lunge. But too much lean and the athlete is buckling under the bag, forcing the erector spinae (lower-back muscles) to fight gravity just to stop the bag sliding over the head.

Not perfectly vertical (that under-uses the glutes), not folded forward (that overloads the lower back) — a controlled slight hinge.

What good looks like

• Torso hinged 5–15° forward, chest proud.
• Bag stays balanced over the base of support.
• The lower back is braced, not working to hold the bag back.

Common faults

Buckling (> 20°)

The torso folds forward under the axial load. The lower back takes over and the bag creeps forward toward the head — the lumbar-overload pattern on this station.

Causes: fatigue, weak trunk endurance, or too heavy a bag for the athlete's brace.

Effect: lumbar strain, bag drifting forward, slowing pace.

Bolt Upright (< 4°)

Perfectly vertical. Safe, but recruits less glute than a slight hinge — leaving drive on the table.

Coaching cues

• "Soft hinge, chest proud" — finds the productive lean without folding.
• "Brace before you step" — sets the trunk before loading.

How to draw

1. Pause on the knee-touch frame.
2. First point: greater trochanter (hip).
3. Second point: acromion (shoulder).
4. The acute angle vs vertical is the reading.

Related measurements

• Trunk Rise (Stripper Lunge) — whether this trunk angle holds as the athlete stands up.
• Front Shin Angle at Depth — the lower-body half of the bottom position.