Trainability of underwater breath-holding time

From diving practice we know that breath-holding time (BHT) can be increased by training. This examination was set up to illuminate whether BHT underwater can be trained decisively in a short period of time. The authors investigated whether physiologic or psychological aspects are the main constituents of the above-mentioned BHT phenomenon. BHT and the "onset point" of involuntary respiratory movements of 64 subjects were registered after deep inspiration and immersion in ca. 1 m. Two different tests were set up: (I) 2 breath-holds per day on 5 consecutive days, (II) 5 repeated breath-holds with pauses of 3 min in between. BHT of the first test was shorter underwater than in similar experiments in air; the increase of BHT underwater was distinctly higher (series II: 160%). Thirty percent of the subjects inequivocally showed respiratory movements (group 1), 31% did not reach the "onset point" (group 3). In group 1 BHT was considerably higher than in group 3. In group 1 the mean time span without respiratory movements rose by 14% in series I and by 233% in series II, whereas the time span with respiratory movements rose by 105% and 119%. These results confirm and quantify the good trainability of BHT underwater. Two processes cause this increase: the increase in time span without respiratory movements probably by unconscious hyperventilation and the increase in time span with respiratory movements through psychological adaptation by suffering the need to breathe.