You Relax — and Your Arm Floats Up All by Itself

Human Body Wonders #1

The Takeaway

Press your arms hard against a door frame for about 30 seconds, then relax — and your arm will slowly float upward, completely independent of your will.

You can try this right away, within safe limits.

• Do not try it if you have pain in your shoulder or arm
• Stop immediately if it starts to hurt
• Do it somewhere with nothing around you to bump into

Here is how to try it.

1. Stand inside a door frame
2. Spread both arms out to the sides, with the backs of your hands against the frame on either side
3. Push against the frame for about 30 seconds, in the direction of opening your arms outward
4. Step forward out of the frame and let both arms go completely limp
5. Do not try to hold your arms down — just watch what happens

If it works, the arm you thought you had relaxed will drift softly upward.

You have no sensation of lifting it yourself. If anything, the arm feels lighter, as if it were floating up on its own.

This is a long-studied effect known as the Kohnstamm phenomenon. It is known to occur because, after a muscle has produced strong force for a sustained period, an “after-contraction” takes place in that muscle.

Why does this happen?

While you are applying force, the muscles that open your arms to the sides keep working hard. As that state continues, the systems that regulate movement are left, for a while, with a lingering setting of “still producing force.”

The leading explanation is that even after you relax, that residual activity combines with the sensory signals coming back from your muscles and joints, and the contraction in the direction of raising the arm continues.

Research suggests that neither central adaptation in the brain and nervous system alone, nor sensory signals from the muscles alone, explains it best — the “mixed theory,” in which both are involved, fits the evidence best.

In other words, the mechanism has not yet been fully settled.

Even so, the phenomenon itself is unmistakable. Without any intention of “lifting,” the body starts moving on its own.

Our everyday movements feel as though they are entirely under the control of our own will.

In reality, though, there are many regulatory systems that keep working outside of our intentions. This floating arm is a moment when one of them surfaces.

If you are in a room with a door frame, give it 30 seconds and try it.

References

• Experimental Brain Research, “Experimental investigations of control principles of involuntary movement: a comprehensive review of the Kohnstamm phenomenon”
• Frontiers in Behavioral Neuroscience, “Sensorimotor organization of a sustained involuntary movement”