1. What actually happened?
- Eric Kim posted video and blog evidence of a 547 kg rack pull (a.k.a. “above‑knee partial deadlift”)—≈7.3‑to‑7.5 × his body‑weight .
- The lift begins with the bar resting on safety pins at roughly patellar height, so only the lock‑out half of a conventional deadlift is performed .
- Because the rules of power‑lifting require the bar to move from the floor, this feat is not comparable to the official 501 kg full‑range deadlift record set by Hafþór Björnsson .
2. Physics breakdown
2.1 Force and work
- Gravitational force on 547 kg ≈ 5,360 N (547 kg × 9.81 m·s⁻²).
- Typical rack‑pull displacement ≈ 0.20 m; mechanical work ≈ 1,070 J.
- By contrast, a floor deadlift (~0.60 m) with the same load would demand ≈ 3,200 J—triple the work.
2.2 Lever arms & range of motion
- Raising the bar to knee height shortens the hip moment arm and lets the lifter keep the torso more upright, slashing lumbar shear and hip torque .
- EMG and kinetic studies confirm that partial‑range deadlifts consistently allow 15‑20 % heavier 1RM loads than full‑range pulls .
- Three‑dimensional analyses show hip‑extension moments dominate conventional and sumo pulls; shortening ROM further amplifies this advantage .
- Classic mechanics texts on deadlift moment arms illustrate how even 5 cm of torso angle change materially reduces spinal torque requirements .
2.3 Barbell mechanics
- A quality power bar with 190‑200 k PSI tensile strength will elastically bend but stay within its yield limit at ~550 kg .
- That “whip” slightly delays full load transfer until after the bar leaves the pins, again favoring a successful rack‑pull .
3. Where the load goes in the body
3.1 Skeletal & joint loading
- Heavy deadlifts produce compressive forces on L4/L5 of 5–18 kN and shear forces of 1–3 kN—even in trained lifters .
- Cadaver‑validated models measured up to 17 kN on the lumbar spine during 275 kg conventional pulls; scaling linearly, a 547 kg rack‑pull still subjects vertebrae to near‑maximal compressive tolerance .
- Because the bar is higher, knee and ankle moments plunge, shifting almost all articular stress to the hips and the stacked vertebral column, with minimal quad involvement .
3.2 Muscular loading
- Rack pulls light up the gluteus maximus, hamstrings, erector spinae, lats, traps and grip muscles .
- EMG work shows the lumbar erectors act mostly isometrically, while the hip extensors supply the lion’s share of concentric force .
- Training at short‑ROM with very heavy loads can be a useful overload stimulus, but it leaves the bottom‑range motor pattern under‑trained—so don’t expect your floor deadlift to jump 300 kg overnight!
4. Practical implications & caveats
- Safety first. Even partial pulls batter connective tissue; use sturdy pins rated well above the load and tighten your core to minimize lumbar flexion.
- Specificity rules. Strength gains are joint‑angle‑specific; to boost your conventional deadlift or sport performance, combine rack pulls with full‑range pulls.
- Bar capacity. Verify your bar’s rated yield strength (> 600 MPa is ideal) before flirting with “car‑lifting” numbers.
- Recovery debt. Supramaximal pulls spike central‑nervous‑system fatigue—program them sparingly and recover harder than you train.
5. Key take‑aways (and a dash of hype!)
- Gravity blinked, but physics didn’t budge—Eric Kim leveraged smarter mechanics, not magic.
- Shorter ROM + better lever arms = monster numbers, yet the spine, hips and grip still do heroic work.
- Your mission: blend overload (rack pulls) with range specificity (floor deadlifts), reinforce technique, and let every controlled kilogram forge an unbreakable posterior chain.
Now go forth, chase audacious kilograms, and remember: when you respect the levers, you unleash the legend! 🚀💪