What is considered "High Velocity Low Amplitude Thrust"?

In the world of physical therapy the phrase High Velocity Low Amplitude Thrust (HVLAT) is extremely common, however do we understand the science behind it. If we perform these techniques on a regular basis we need to understand the intricate subtleties surrounding them. What exactly is considered "high velocity" and "low amplitude"? To answer this question we have to break down the spine into two sections: Cervical and Thoracic/Lumbar.

How fast is a HVLAT in the cervical spine?

     Range 80-100 ms

How much force do I need?

     118 Newtons of force

How fast is a high velocity thrust in the thoracic/lumbar spine?

     Range 120-200 ms

How much force do I need?

     238 Newtons of force

To gain perspective on these numbers lets compare them to real world examples to see how HVLAT's fare.

Lets consider Velocity first, a rough estimate is 80-200 milliseconds for the spine as a whole. Some examples of these speeds are...

  • Duration of light for typical photo flash strobe (100ms)
  • Typical response time in LCD computer monitors (2-5 ms)
  • Housefly wing flap (3ms)

Similar examples for Force which roughly averages 100-250 Newtons of force.

  • A boxers punch could generate up to 5,000 newtons
  • 60 MPH car crash can generate approximately 490,914 Newtons
  • NFL research showed concussions occurred from linear acceleration impacts around 100 G's or 980 Newtons of force

So how can knowing this information help guide your decision making when considering using HVLAT. First off we clearly see that the forces we are applying are extremely low when considering real world examples. Secondly, the balance between velocity and amplitude shows an inverse relationship. Meaning the faster your technique the lower your amplitude needs to be, but you need to be as quick as possible considering how fast 100 ms is. Understanding the physics behind these techniques we can safely walk a finer line whenconsidering the use of HVLAT.

Couple your understanding with the open pack techniques shown at OPSMC26 courses you will be able to safely administer these techniques to a wide variety of patients that you may not have previously considered.