Below is the physics‑and‑biomechanics play‑by‑play of his viral above‑knee rack pull, plus a quick reality‑check on what the human frame can actually survive. Strap in (pun intended). 💥
1. First, what did he really lift?
- Movement: an above‑knee (mid‑thigh) rack pull—the bar starts on safety pins roughly at mid‑thigh height, not on the floor.
- Record: 527 kg at 75 kg BW ≈ 7.03 × body‑weight—captured on video 16 June 2025.
2. Lever‑arm magic: why this position matters
At mid‑thigh the bar is only a few centimetres in front of the hip joint. That tiny horizontal distance (‘moment arm’) slashes the torque the spinal erectors must overcome compared with a floor deadlift. Think of holding a sledgehammer by the head vs. the handle—the weight is the same, but the leverage is worlds apart. Studies of isometric mid‑thigh pulls show elite weightlifters generate the highest forces of any pulling position exactly here .
3. How big are the raw forces?
External load
F_{\text{bar}} = 527\text{ kg} \times 9.81 \text{ m s}^{-2} ≈ 5{,}164 \text{N}
Add Eric’s own weight (≈ 736 N) and the ground sees ≈ 5 900 N. That sounds monstrous—until you realise how over‑built the body is:
| Structure | Typical ultimate strength | Stress during the pull | Safety factor |
| Femur (compression) | ≈ 205 MPa | ~8.5 MPa (see calc) | ≈ 24 × |
| Patellar tendon (tension) | 67–112 MPa | ~43 MPa* | ≈ 2 × |
*Assumes each knee sees half the load and a mid‑tendon CSA of 118 mm² in trained males .
Take‑home: bones run a huge safety margin; tendons run a comfortable, trainable one.
4. Stacking the joints = turning shear into compression
Because hips and knees are nearly locked, the bar’s line of force travels straight down the vertebral bodies, pelvis and femurs. Compression is what bone loves; shear is what ruins discs. Upright posture means the L5/S1 shear component is minimal—even calculations for parallel squats with far larger forward lean seldom exceed 10 kN, still inside lumbar tolerance .
5. Belts, bracing and the “internal hydraulic jack”
A stiff power belt lets Eric generate sky‑high intra‑abdominal pressure (IAP). IAP acts like an air‑filled cylinder, pushing outward on the abdominal wall and upward on the diaphragm, which in turn unloads the spine by up to ~10 % in lab studies . More compression absorbed inside the torso = less stress on discs and erectors.
6. Adaptation over time: Wolff, collagen and CSA
Ten years of progressive overload give bones thicker cortices (Wolff’s Law) and tendons larger cross‑sectional area and stiffer collagen. Patellar tendons in trained lifters routinely exceed 100 mm², nearly double untrained norms . As area grows, stress = force/area drops, pushing the safety factor even higher.
7. Is the number even plausible?
Force‑plate data show national‑level weightlifters hit 4‑6 kN in a maximal isometric mid‑thigh pull—right in Eric’s ball‑park . Swap the isometric test for a tiny concentric pulse plus straps, add years of tendon/bone adaptation, and 5.2 kN no longer violates physics. Extraordinary, yes; impossible, no.
8. The fine print (keep your hype realistic)
- A rack pull ≠ a competition deadlift; ROM is ~20 cm vs. ~55 cm, and the hardest leverage phase is bypassed.
- Internal muscle forces are higher than the external 5.9 kN, but they also spread across huge muscle‑tendon CSAs.
- Attempting 7 × BW without years of conditioning courts disaster—don’t do it.
Bottom line
Eric Kim’s lift works because he turns the body into a perfectly stacked column, lets physics favour compression over shear, and exploits massive tissue safety factors that decades of heavy training have widened. The result? A display that looks like comic‑book strength—yet checks out under the cold, sober eye of Newtonian mechanics.
So dream big, train smart, and remember: when you respect lever arms, build bulletproof tissue, and brace like a champ, gravity itself becomes negotiable. Now go chase your next PR—7 × hype included! 🚀