Sandbag Lunge — Rep Rate

Why this matters

The sandbag lunge is a loaded, ground-covering grind: a sandbag on the shoulders, walking lunges for 100 m. Rep rate is the pacing read, and the trade-off it captures is rate vs. quality of each rep. Too slow usually means long ground-contacts and a rest pause at the top of each step — the athlete is recovering between reps instead of moving. Too fast under load risks rushing the depth or letting the front knee track inward, which is both slower (a shallow lunge may not meet the standard) and a load the knee doesn't want to take 100 times.

Because each lunge also covers ground, rep rate pairs with Stride Length: a longer lunge stride covers more ground per rep but loads the front knee harder, so fewer slower reps; a shorter stride means more, lighter reps. The fastest sustainable split is the combination the athlete can hold with clean depth under the sandbag.

How it's measured here — and the slow-motion trap

This is a windowed count. Scrub to the start of a clean rep (e.g. the bottom of a lunge) to open the window, scrub to the same point of a later rep to close it, count the reps between. Rate = reps ÷ window-seconds × 60.

If the clip is phone slow-motion (120/240 fps captured, 30 fps timestamps), an uncorrected rate reads 4–8× low. Set Capture FPS in the Clip Inspector to the true capture rate so the tool rescales to real time.

What good looks like

12–20 reps/min held steady across the 100 m, each rep reaching clean depth with the front knee tracking over the foot and no rest pause at the top. Steady cadence under control.

Common faults

• Slow (< 12 reps/min) — long ground-contact and a rest at the top of each step. Sustainable but slow; if depth and tracking are solid there's room to keep the feet moving.
• Fast (> 20 reps/min) — risks rushing depth (missing the standard) or letting the front knee collapse inward under load. Speed isn't worth a no-rep or a cranky knee at rep 60.
• Decaying rate with degrading depth — the dangerous combination: as the rate sags the depth often gets shallower, not deeper. Cross-check front-knee flexion late in the effort.

Coaching cues

• "Stand tall, sink straight down — don't lean over the bag." Keeps depth honest at a steady rate.
• "Knee tracks over the toes." Protects the front knee when the rate is up.

Related measurements

• Stride Length — the ground each rep covers; the other half of the lunge pacing equation.
• Front Knee Flexion at Depth — confirms depth holds as the rate is pushed.