G-force Impact on Human Body

G-force Impact on Human Body

In vibration therapy, movement acceleration plays important role and makes vibration therapy unique.

Acceleration is created when an object’s velocity changes. In vibration motion, the object velocity keep changing in reverse directions. So vibration acceleration also keeps changing between the maximum value and the negative maximum value.

When you stands on a running vibration plate, your body experiences the acceleration created by the vibration plate. This article discusses the impact of vibration acceleration on human body in whole-body vibration exercise.

Vibration G-force

For topics related to acceleration’s impact on human body, G-force is usually used as the unit to express the value of acceleration rate.

G is the acceleration of gravity. To reiterate, G-force is not a force, but an acceleration rate. Using G makes it easier to comprehend the magnitude of acceleration, because we experience every day.

Acceleration Force

When you stand on the ground, the earth gravity tends to pull you downward, but the ground stops the tendency. 

In this situation, your acceleration rate, is 1G, and you experience an acceleration force of 1G times your body weight.

Let’s say you weigh 200LB. At 1G, there is a 1x200LB acceleration force pulling you down. Your body overcomes the 200LB gravity, and you feel your weight is 200LB.

Our body systems, organs and tissues are all used to the 1G acceleration environment in which we live on this earth.

Now you step on to a running vibration plate. At a moment, it pushes you up at an acceleration of 3G, your body will need to overcome 3x200LB=600LB downward acceleration force.

In this situation, you feel your body weight is 600LB.

In vibration motion, the upward acceleration motion only happens in the 4th phase of a vibration circle. If the vibration frequency is 30Hz, each vibration cycle takes 1/30 second. The upward acceleration is only 1/4 circle. That mean, in a vibration circle, the time period you experience 600LB is a tiny 1/120 second (0.008 second).

To summarize, if you weigh 200LB and you use a vertical movement vibration plate that vibrates at 30 Hz with G-force of 3. For every second, you will experience your body weight surging to 600LB for 30 times, each time lasts 0.008 second.

This explains the pattern of mechanical impact that occurs in vibration exercise. In one phrase: repeated short pulses of intensive mechanical impact.

In realty, the 600LB acceleration force is only at the bottom of your feet against the vibration plate. Above the feet, your flexible body absorbs some vibration, and G-force is reduced, so as the acceleration force.

Impact of High G-force

In vibration plates available in the market, G-Force is mostly designed to falls in the range from 2G to 8G.

For the comparison, a powerful fighter jet can reach an acceleration rate as high as 9G. A human payload rocket has a 3G at launch and up to 8G at re-entry.

Blood flux and blood turbulence

Vertical direction G-force on a upright human causes blood to flux from the head to the feet, or reverse direction in case of negative G-force.

Prolonged high G-force can cause blood supply problems at brain and eyes, and can cause loss of consciousness (G-LOC) or loss of vision.

For flying a high performance fighter jet, extended high G exposure can be fatal.

In vibration exercise, the high G situation only lasts for a tiny fraction of a second, then the movement direction is reversed.

This quick reverse G-force pattern only causes blood turbulence, not blood flux in one direction. It should not cause serious problem for brain blood supply.

Some people can get dizzy when vibration is transmitted to their heads. It can be either blood supply issue or never issue, or, a combined effect.

There are cases that people experience loss of vision when vibration is transmitted to the head. Eye retina is very sensitive to low blood pressure. Insufficient blood supply can cause the retina not to function properly.

Prolonged insufficient blood supply can cause permanent damage to retina.

Vibration’s impact on eyes has not been well studied. Negative reports on vision loss are very few.

Generally, people can get blurred vision during vibration. That is mainly because it is difficult to focus while eyes are in motion.

Mechanical impact

The other impact of high G in vibration exercise is the acceleration force’s mechanical impact on our body.

Because the acceleration force takes the form of repeated short pulse and immediately released when the movement direction reversed. Our body can take this type of repeated short pulses of intensive mechanical stimulation well.

In fact, this intensive mechanical stimulation is an unique attribute of vibration therapy. Scientists consider it valuable in their exploration of utilizing this unique stimulation for health benefits.

Vibration Hazards

Vibration hazards may not be exactly relevant to the discussion of iG-force in this article, but it makes sense to put this information here because it is also safety related.

Extended exposure to vibration can be hazards. This mainly pertains to profession related exposure like operating tools and machinery that produce intensive vibration.

In the US, there is not a set of regulated safety standard for profession related vibration exposure. US Labor Department and National Institute for Occupational Safety and Health (NIOSH)  published advisory information on hand-arm vibration exposure. NIOSH published more detailed recommendation for the standard.

Hand-arm vibration syndrome or “white fingers” is related to consecutive hours of using certain electric hand tools. This includes damage to nerves, soft tissue or joints of the hand, wrist and arm,

In other publications, researchers try to find relationship between vibration hazards and the frequency, but there have seemed no consistent results achieved.

In vibration exercise, the use of vibration plate is usually less than 20 minutes a time, one or two times a day. This  is not considered as extended exposure, but users should be aware the potential hazards of extended exposure in vibration.

In conclusion, in vibration exercise, G-force usually does not have negative impact on human body.

On the other hand, the short pulses of intensive acceleration force may create the needed mechanical stimulation for health benefits.

In regular vibration exercise, if it is not excessive, vibration is not considered as a hazard. In many clinical trials conducted to test vibration therapy’s efficacy, scientists did not find prove of side effect, and their conclusion is vibration exercise is safe.

People with serious medical condition especially those with implants, should do thorough research and consult medical professionals for advise before performing vibration exercise.

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[…] October 1, 2020 […]

Jay

Interpreting life science from a mechanical engineering background. Contact: jay@vibrationcare.com