Sled Push · Knee Extension at Push-Off

Why this matters

Knee extension at toe-off measures the length of the drive stroke — how far the back leg actually extends before it lifts to swing forward.

A heavy sled rightly prevents a true 180° lockout; that's expected and fine. But if the knee only reaches 120–130°, the athlete is taking short, panicked, choppy steps. They cover almost no ground per stroke while spiking cadence and heart-rate — the worst trade in the race, because the run segments come next.

What good looks like

• Drive leg extends to a long, near-straight line at toe-off.
• Each step visibly moves the sled.
• Cadence is controlled, not frantic.

Common faults

Choppy Steps (< 140°)

The defining mechanical-efficiency fault. The drive leg never finishes its stroke, so each step barely advances the sled while the athlete's heart-rate climbs.

Causes: sled too heavy for the athlete's current strength, panic under load, or a habit of fast feet over long drives.

Effect: wasted strokes, HR spike, slow split, and a fatigued athlete arriving at the next run.

Partial (140–150°)

Almost a full stroke — a small amount of length left on the table. Minor refinement.

Coaching cues

• "Drive all the way through" — extends the stroke to completion.
• "Long pushes, not fast feet" — trades cadence for stroke length.
• Train lighter — reduce the load so the athlete can groove a full stroke, then progress.

How to draw

1. Pause on the final frame the back (drive) foot is on the carpet, right before it lifts to swing.
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

• Hip Extension at Push-Off — same frame; confirms the glutes (not just the quads) finish the stroke.
• Shin Angle at Contact — the front leg planting as this back leg finishes.