905.8 kg (1,997 lb)

 overload pull can be physically possible

What makes “super-human” looking numbers possible in a rack pull / partial deadlift isn’t magic—it’s mechanical advantage + joint-angle strength curves + bracing + tendon stiffness + neural drive, all lining up at the strongest point of the lift.

Below is the science, in plain English—but ruthless.

1) External load ≠ the force your muscles “feel”

A barbell is an external load. Your body “pays” that load through joint torques:

Torque = Force × moment arm

So if the bar is closer to your hips/spine (shorter moment arm) and your torso is more upright, you need less spinal/hip torque to hold the same weight. That’s the first cheat code of partials: they often put you in a more favorable geometry than pulling from the floor. 

2) Partial range of motion deletes the weakest part of the lift

A floor deadlift forces you through:

  • maximal knee bend + hip flexion
  • longer moment arms
  • worse leverage off the floor

A rack pull starts higher—often around the knee or above—so you skip the “break off the floor” problem and begin closer to the joint angles where humans can produce higher isometric and near-isometric joint moments. This is a big reason partials routinely allow much heavier loads than full ROM. 

3) Strength is joint-angle specific (your body has “peak angles”)

Muscle force output changes with joint angle because of:

  • muscle length–tension behavior
  • moment-arm changes
  • muscle architecture / pennation shifts
  • neural recruitment differences at specific angles

Research modeling/measurement shows isometric joint moments vary substantially across hip and knee angles—meaning there are positions where your system is simply built to be strongest. 

Rack pulls often live closer to those “money angles.”

4) A heavy rack pull is closer to a maximal isometric than a full dynamic lift

At extreme loads, the first millimeters matter most: you’re trying to break inertia and then finish a short, mechanically favorable range.

That makes the effort functionally similar to a max voluntary isometric contraction (MVIC) at a strong angle—where humans can express huge force for a brief window. Joint-angle specific recovery and adaptation research also supports the idea that isometric strength and adaptation are angle-dependent, reinforcing why partials can spike numbers. 

5) Bracing (Valsalva) turns your torso into a pressure cylinder

For monster loads, your spine can’t be “soft.” The body uses the Valsalva maneuver to raise intra-abdominal pressure (IAP), which increases trunk rigidity and helps stabilize the spine under heavy lifting. 

Think of it like inflating an internal airbag that stiffens the whole chassis.

6) Tendon + connective tissue stiffness = better force transfer

With heavy training, tendons adapt—often becoming stiffer (via changes in modulus and structure). A stiffer series elastic component can improve how efficiently muscle force transmits to the skeleton (less “energy lost” in slack). 

At the extreme end, the limiting factor can shift away from “muscle strength” toward tissue tolerance + bracing + position.

7) The nervous system can “unlock” force briefly

Maximal efforts rely on:

  • high motor unit recruitment
  • high firing rates
  • synchronization
  • arousal / intent

That’s why “one all-out pull” can exceed what you can repeat for reps. It’s not just muscles—it’s the CNS turning on every available resource (especially in a short ROM, where fatigue time is minimal).

8) Why the number is plausible 

as a phenomenon

—even if it’s rare

A 905.8 kg external load corresponds to ~8,900 N of weight force, but the key is that in a partial:

  • the ROM is shorter
  • the leverage is better
  • the lift may be closer to isometric at strong angles
  • IAP/bracing can be maximized
  • tendon stiffness + technique reduce “energy leaks”

That combo is exactly what lets partial pulls jump far beyond full deadlift numbers. 

Safety note (still hardcore, still real)

The physics that make huge partials possible are the same physics that can punish you if position slips: spinal shear/compression, tissue strain, equipment failure. If you’re pushing overload work, the “science” approach is progression, setup quality, and equipment rated for the load—no chaos.

If you want, I can turn this into a formal “journal-style” article (Abstract → Methods → Discussion) written like a real biomechanics paper, using your exact setup details (start pin height, ROM, stance, straps/belt, bar type).