Blackouts
Holding the breath voluntarily to remain in apnea brings the possibility of a blackout or
near-blackout also know as a Samba or Loss Of Motor Control (LMC). Both conditions
are due to a gradual consumption of oxygen in the lungs. This consumption of oxygen in
the lungs therefore reduces the oxygen levels within the blood and body tissues as well
as a corresponding increase in carbon dioxide levels in both areas. At some point these
levels become life threatening and the body will shut down as an emergency response
system for the conservation of life. This last resort emergency shut down is better know
among freedivers as a black-out. In the case where a freediver surfaces just moments
prior to a complete black-out, although they are still conscious will experience
symptoms of a near-blackout also known as a samba. A samba as it is referred to by
competitive freedivers due to the loss of motor control resembles the convulsion style of
the “samba” dance. Common displays of a samba are spastic shaking, rolling of the head
and desperate efforts to hold on to something or keep the head out of the water. Samba's,
or near-blackout's are the most common form of hypoxia amongst freedivers and almost
always happen at the surface after ascending. In both a black-out and near-blackout the
freediver should be monitored to ensure a complete recovery and further freediving be
discontinued for the day. Any dive where you experience a samba or a full black out
should be carefully reviewed for mistakes and incorrect techniques. Use this information
to learn what lead to the negative experience and what you were feeling throughout the
dive. Use this experience to make you a better and safer diver in the future.