Shivering heat production and body fat protect the core from cooling during body immersion, but not during head submersion: A structural equation model

Previous studies showed that core cooling rates are similar when only the head or only the body is cooled. Structural equation modeling was used on data from two cold water studies involving body-only, or whole body (including head) cooling. Exposure of both the body and head increased core cooling, while only body cooling elicited shivering. Body fat attenuates shivering and core cooling. It is postulated that this protection occurs mainly during body cooling where fat acts as insulation against cold. This explains why head cooling increases surface heat loss with only 11% while increasing core cooling by 39%.

[1]  J. Leblanc.  Subcutaneous fat and skin temperature. , 1954, Canadian journal of biochemistry and physiology.

[2]  Rex B. Kline,et al.  Principles and Practice of Structural Equation Modeling , 1998 .

[3]  B. Efron.  Better Bootstrap Confidence Intervals , 1987 .

[4]  G. Giesbrecht,et al.  Life jacket design affects dorsal head and chest exposure, core cooling, and cognition in 10 degrees C water. , 2005, Aviation, space, and environmental medicine.

[5]  G G Giesbrecht,et al.  Effect of task complexity on mental performance during immersion hypothermia. , 1993, Aviation, space, and environmental medicine.

[6]  M. J. Rack,et al.  Calorimetry with heat flux transducers: comparison with a suit calorimeter. , 1983, Journal of applied physiology: respiratory, environmental and exercise physiology.

[7]  The perceptual and physiological responses of high and low fat women exposed to 5°C air for 120 minutes , 1998 .

[8]  D. Nelson,et al.  Brain temperature and limits on transcranial cooling in humans: quantitative modeling results , 1998, European Journal of Applied Physiology and Occupational Physiology.

[9]  Karl G. Jöreskog,et al.  Lisrel 8: User's Reference Guide , 1997 .

[10]  G. Giesbrecht,et al.  Thermal effects of dorsal head immersion in cold water on nonshivering humans. , 2005, Journal of applied physiology.

[11]  R. MacCallum,et al.  Power analysis and determination of sample size for covariance structure modeling. , 1996 .

[12]  Peter Tikuisis,et al.  Thermoregulatory model for prediction of long-term cold exposure , 2005, Comput. Biol. Medicine.

[13]  P. Bentler,et al.  Cutoff criteria for fit indexes in covariance structure analysis : Conventional criteria versus new alternatives , 1999 .

[14]  A C BURTON,et al.  Heat losses from the human head. , 1957, Journal of applied physiology.

[15]  P Tikuisis,et al.  A mathematical model for human brain cooling during cold-water near-drowning. , 1999, Journal of applied physiology.

[16]  T. Wilson,et al.  Skin-surface cooling elicits peripheral and visceral vasoconstriction in humans. , 2007, Journal of applied physiology.

[17]  G G Giesbrecht,et al.  Decrement in manual arm performance during whole body cooling. , 1992, Aviation, space, and environmental medicine.

[18]  K. Metz,et al.  Physiological and thermal responses of males with varying body compositions during immersion in moderately cold water. , 1991, Aviation, space, and environmental medicine.

[19]  W. Engel.  The Treatment of Shock from Prolonged Exposure to Cold , 1947 .

[20]  A. Tomarken,et al.  Structural equation modeling: strengths, limitations, and misconceptions. , 2005, Annual review of clinical psychology.

[21]  P. Webb.  Afterdrop of body temperature during rewarming: an alternative explanation. , 1986, Journal of applied physiology.

[22]  P. Bentler,et al.  Comparative fit indexes in structural models. , 1990, Psychological bulletin.

[23]  A. Hope.  A Simplified Monte Carlo Significance Test Procedure , 1968 .

[24]  Keith F Widaman,et al.  On specifying the null model for incremental fit indices in structural equation modeling. , 2003, Psychological methods.

[25]  Peter M. Bentler,et al.  Estimates and tests in structural equation modeling. , 1995 .

[26]  W. Santee,et al.  Thermal responses for men with different fat compositions during immersion in cold water at two depths: prediction versus observation , 2007, European Journal of Applied Physiology.

[27]  G. Giesbrecht,et al.  Thermal effects of whole head submersion in cold water on nonshivering humans. , 2006, Journal of applied physiology.

[28]  G. Ferretti,et al.  Superficial shell insulation in resting and exercising men in cold water. , 1982, Journal of applied physiology: respiratory, environmental and exercise physiology.

[29]  G. Giesbrecht,et al.  Shivering Heat Production and Core Cooling During Head-In and Head-Out Immersion in 17°C Water , 2008 .