Where does crush collide?

In medicine, crush syndrome is the systemic consequence of prolonged compression of large muscle masses: when pressure is released, damaged muscle releases myoglobin, potassium, and other contents into the circulation, which can cause acute kidney injury, hyperkalaemia, and shock. Bywaters and Beall described the syndrome and its renal failure in victims pulled from bombing rubble. The referent is a traumatic-metabolic emergency in the body, unrelated to grapes except through the shared idea of being crushed.[1]

Unit

Systemic metabolic injury following release of a prolonged crushing force on muscle

Recovery means

Renal and metabolic function can recover with early fluid resuscitation and management before the compression is released

Measured by

Tracked by serum creatine kinase, myoglobin, potassium, and renal-function markers

In the physics of pedestrian crowds, a crowd crush (or progressive crowd collapse) occurs when density becomes so high that individuals lose control of their movement, shock-wave-like pressures propagate through the mass, and people are compressed or trampled, a failure mode distinct from ordinary flow. Helbing, Johansson, and Al-Abideen analysed video of a crowd disaster and identified transitions from laminar to "stop-and-go" and "turbulent" crowd motion preceding the catastrophe. The referent is an emergent collective phenomenon in dense human crowds, not a bodily injury or a winery step.[2]

Unit

The onset of turbulent, high-pressure motion and collapse in a dense crowd

Recovery means

Not applicable

Measured by

Detected from crowd density, velocity fields, and the "crowd pressure" derived from video analysis