Aviation, Space, and Environmental Medicine x Vol. 78, No. 11 x November 2007 1029 RESEARCH ARTICLE Breath-Hold Time During Cold Water Immersion: Effects of Habituation with Psychological Training Martin J. Barwood, Avijit K. Datta, Richard C. Thelwell, and Michael J. Tipton B ARWOOD MJ, D ATTA AK, T HELWELL RC, T IPTON MJ. Breath-hold time during cold water immersion: effects of habituation with psy- chological training. Aviat Space Environ Med 2007; 78:1029–34. Introduction: The loss of the conscious control of respiration on whole body cold water immersion (CWI) can result in the aspiration of water and drowning. Repeated CWI reduces the respiratory drive evoked by CWI and should prolong breath-hold time on CWI (BHmax CWI ). Psy- chological skills training (PST) can also increase BHmax CWI by improving the ability of individuals to consciously suppress the drive to breathe. This study tested the hypothesis that combining PST and repeated CWI would extend BHmax CWI beyond that seen following only repeated CWI. Methods: There were 20 male subjects who completed two 2.5-min, head-out breath-hold CWI (BH1 and BH2) in water at 12°C. Following BH1, subjects were matched on BHmax CWI and allocated to a habitua- tion (HAB) group or a habituation plus PST group (H 1PST). Between BH1 and BH2 both experimental groups undertook five 2.5-min CWI on separate days, during which they breathed freely. The H 1PST also re- ceived psychological training to help tolerate cold and suppress the drive to breathe on immersion to extend BHmax CWI . Results: During BH1, mean BHmax CWI ( 6 SD) in the HAB group was 22.00 (10.33) s and 22.38 (10.65) s in the H 1PST. After the five free-breathing CWI, both groups had a longer BHmax CWI in BH2. The HAB group improved by 14.13 (20.21) s, an increase of 73%. H 1PST improved by 26.86 (24.70) s, a 120% increase. No significant differences were identified between the groups. Conclusion: Habituation significantly increases BHmax on CWI, the addition of PST did not result in statistically significant im- provements in BHmax CWI , but may have practical significance. Keywords: drowning, head-out immersion, psychological training. B REATH HOLDING is the conscious suppression of the drive to breathe. This drive can come from vari- ous sources including the desire for respiratory move- ment, an increase in blood hydrogen ion concentration, or a decrease in the oxygen tension of the blood (5,8,30). Sudden cooling of the skin, in particular to the torso (3), during cold water immersion (CWI) can also evoke a powerful drive to breathe as stimulation of peripheral cold receptors initiates the “cold shock” response (9,21). During head-out immersion, most individuals are un- able to suppress this drive to breathe and their maxi- mum breath hold time (BHmax) is significantly reduced compared with that achievable in air (17,21). This re- sponse is potentially hazardous, representing a precur- sor to the aspiration of water and drowning (24). The diminution of BHmax on CWI (BHmax CWI ) is a potential problem for those at daily risk of accidental immersion (e.g., helicopter pilots) and has led to the provision of protective clothing (25,29) and equipment (23,28). For those without such protection, the possibil- ity of extending BHmax CWI by physiological means re- mains the only option. In theory, BHmax can be extended by reducing the drive to breathe or improving an indi- vidual’s ability to consciously suppress that drive. It is well established that as few as five 3-min CWI can re- duce the respiratory responses by about 50%, and this reduction remains, in part, for at least 14 mo (26). Tipton et al. (22) showed habituation occurred centrally to the peripheral cold receptors and the role of central brain structures has been further supported by animal and human studies (7,10). Assuming that the relationship be- tween BHmax CWI and respiratory drive is linear, reduc- ing the respiratory drive during CWI should increase BHmax CWI . However, the habituation of BHmax CWI has not been studied. With regard to improving the ability of individuals to suppress the drive to breathe on CWI, Barwood et al. (2) have recently reported that psychological skills training (PST) improved BHmax CWI by an average of 80%. In theory, therefore, BHmax CWI can be increased by one of two means: by decreasing the afferent drive to breathe (habituation); and/or by increasing the ability of indi- viduals to tolerate that drive (PST). This characterizes habituation and PST as independent processes, the combination of which has the potential to increase BHmax CWI beyond that of habituation alone. This study tested the hypotheses that repeated CWI would significantly extend BHmax CWI by reducing the car- diorespiratory component of the cold shock response and that the increase recorded in BHmax CWI would be greater when repeated immersion (habituation) was supplemented by PST. Department of Sport and Exercise Science, University of Ports- mouth, Portsmouth, UK. This manuscript was received for review in March 2007. It was accepted for publication in July 2007. Address for correspondence: Dr. Martin Barwood, Dept. of Sport and Exercise Science, Spinnaker Building, White Swan Road, Uni- versity of Portsmouth, Portsmouth, Hants. PO1 2ER, UK; martin. barwood@port.ac.uk Reprint & Copyright © by Aerospace Medical Association, Alexan- dria, VA. DOI: 10.3357/ASEM.2100.2007