Dear Science,
Many years ago when I was in college, I used to do push-ups in my
dormitory room. A couple of times, my roommate decided to crack jokes
about me in the middle of my set, and invariably I would start
laughing, suddenly lose all of the strength in my extremities, and crumple up into a limp mass on the floor. Recently I
was exercising at home, and my wife made me chuckle while I was in the
middle of a set of pull-ups; once again, I found myself drained of all
strength and unable to move an inch toward the bar. So my question
is: Why does laughter drain the strength from my body for several seconds and make me as weak as Superman after
a kryptonite enema? Does everyone suffer the same kind of
reaction? Does this have to do with laughter being a kind of convulsion
or something?
Laughter = Kryptonite
Yup, it happens to everyone. Get prepared for a word that’ll change
your life, for the better or worse: cataplexy, the sudden
physical collapse caused by experiencing strong emotions or laughter.
Why? Now that’s a tougher question.
Feeling weak from laughter appears to be from the temporary
inhibition of the motor neurons—the cellular wires that connect
your brain to your muscles—around the body. How do we know this?
By testing a leg reflex—otherwise known as the
H-reflex—when showing volunteers movies. Start to laugh, and the
reflex goes away. Seeing something funny isn’t enough; one must
actually laugh to bring on the feebleness.
Okay, but why? Two explanations compete for your acceptance. One
says that any really deep breath out causes weakness; a big exhalation
alone can cause the same poor H-reflex. Perhaps the incapacity is just
from breathing out a whole bunch of air at once. The alternative theory
lays the blame at the emotion of mirth, which is accused of sending the
spinal cord into a fit of paralyzing activity. Can deep amusement
itself cause the weakness, independent of the effects on breathing?
Time for a truly awesome study to figure it all out. The dream team
of Overeem, Taal, Gezici, Lammers, and van Dijk assembled. Twice a
second, the H-reflex was measured. Volunteers did 10 different tasks,
including sitting quietly, coughing, faking laughter, and “true”
laughter, caused by scientists telling jokes. “True laughter was
obtained in all participants,” the team noted defensively. “There are
probably two reasons for this high success rate. First, we did our best
to create a relaxed atmosphere conducive to laughter. Second, using a
large stimulating surface electrode… helped to reduce the
pain” of forcing the reflex.
The result? Faked laugher (with a similar effect on breathing as
real laugher) had a much weaker effect than the real thing. The
conclusion? The crazy breathing pattern contributes, but mirth wins the
kryptonite crown.
Gleefully Yours,
Science
Send your science questions to
dearscience@thestranger.com.
