How does gravity and acceleration impact fall protection?

Gravity is an acceleration force that draws two masses together. Because this gravitational acceleration is such an influential force, it is only logical that there are certain circumstances that either increase or decrease the amount of acceleration or “G-forces” imposed upon a human. Many physicists have devoted (and sometimes risked) their lives to study the effects of acceleration. In general, the human body’s ability to tolerate acceleration is based upon the following factors: the magnitude of the acceleration (measured in “G-Forces”), the length of time applied, the direction of the force caused by acceleration, the location on the body where the force is applied, and the position of the human when the acceleration force is applied.

Now, please understand that:
1 g = 9.806 m/s²

This means that any object or body that increases its velocity by 9.806 meters per second every second is experiencing one “g-force”. Thus, the more quickly the body changes its velocity, the more g-forces the body/object experiences. Without the use of any special equipment or suits, the human body can comfortably sustain 5g when moving upwards and -3g when moving downward. The direction of the movement is a large factor in how the human body handles gravitational force.

Acceleration can be applied in two different ways: vertically and horizontally (or a combination thereof). During vertical movement (up or down), the human body is generally less tolerant of G-forces when compared to horizontal movement tolerance (but we will not be discussing horizontal movement at this time).

When discussing vertical acceleration, if a person is accelerating in an upward direction, this is referred to as “Positive G’s”. During a positive g event, the blood will be forced into a person’s feet. If a person is accelerating in a downward direction, that is known as, “Negative G’s”. Negative G’s will force blood flow into the brain. During a free-fall event, a person will experience acceleration.

When a fall event stops, the deceleration device (typically an Energy Absorbing Lanyard) will absorb the energy. But, if the distance of the fall is so great that it rips through all the “rip stitch” energy absorber, then, any of the remaining fall energy must be absorbed by the falling person’s body.

If the person who is using the system has a heavier weight, it will take more energy absorption for their fall to be arrested. Since it will require more energy to arrest the fall, a heavier person on the system will fall farther than a lighter person. Our systems are designed to decelerate workers who weigh between 130 and 310 lbs with 900 lbs Maximum Arresting Force.

REMEMBER: if a system is used improperly and the system cannot absorb all of the energy from the fall event, then the human body must absorb the remainder of the energy (which could cause injury or fatality). As a result, it is critical that the fall protection system be used properly and in accordance with the manufacturer’s instructions.