Wieling and his colleagues in Amsterdam and the US taught 20 adults
with a history of vasovagal fainting to cross their legs and tense
their leg, abdominal and buttock muscles while standing. The
researchers then induced fainting conditions by placing the patients
on a table that can be rotated to an upright position and tilting it
60 degrees for 20 minutes. Patients who failed to become dizzy were
then given nitroglycerine, which induces fainting by dilating blood
vessels, thereby lowering blood pressure. They were then tilted for
another 15 minutes[. flauwvallen]
As soon as the patients showed signs of fainting, they were told to
cross their legs and squeeze their muscles until their symptoms had
subsided for 30 seconds. If the dizziness returned, they were
instructed to resume the manoeuvre until it disappeared.
The manoeuvre prevented loss of consciousness for 5 of the 20 patients.
The remaining 15 were able to postpone a faint by an average of 2.5
Offering a possible explanation, Wieling stated that “leg muscle
tensing squeezes the swollen veins and thereby brings blood back to
the chest.” This enables the heart to pump more blood, which increases
blood pressure and the flow of oxygen to the brain.
The effects of such muscle tensing are comparable to those of putting
your head between your knees, he added.
In follow-up telephone interviews with the study participants about
a year later, the researchers found that 13 of the patients used the
leg-crossing manoeuvre in their daily lives to prevent or control
dizziness and fainting. Only two had fainted since the test.
Therefore, leg crossing and muscle tensing may be a preferable
alternative to a pacemaker for people prone to vasovagal fainting
because it is easy to perform and effective, without any side effects,
the authors conclude.
They add that by enabling people to prevent or delay loss of
consciousness, the manoeuvre “can increase patients’ sense of control
over their symptoms and thereby improve their quality of life.”