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  • 1
    Electronic Resource
    Electronic Resource
    Is energy substrate mobilization a limiting factor for cold thermogenesis? (1993)
    Springer
    European journal of applied physiology 67 (1993), S. 239-244 
    Details
    ISSN: 1439-6327
    Keywords: Body temperatures ; Energy metabolism ; Heat balance ; Heat production ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Energy substrate mobilization has been suggested as being a limiting factor for the rate of cold-induced thermogenesis (M), and consequently in delaying hypothermia. The evidence supporting this hypothesis in humans, however, is not convincing and the hypothesis has yet to be tested in a rigorous manner using a full heat balance analysis (partitional calorimetry). The goal of this study was therefore to re-investigate whether enhancing energy substrate mobilization by feeding cold-exposed subjects would improveM and affect heat debt (S; the minute-by-minute balance ofM and heat losses) as well as rectal (T re) and mean skin temperatures $$\bar T_{sk} $$ . Nine healthy semi-nude fasted subjects were exposed to 5° C (3 h at rest, 1 m · s−1 wind) on three occasions following the ingestion at min 0 and 90 of either: (1) a placebo, (2) 710 kJ of pure carbohydrates (100%-CHO), or (3) 710 kJ of a high-carbohydrate bar (High-CHO). As expected in the cold,T re andT sk decreased whereasM, S and heat losses increased (P〈0.01). However, there were no differences between treatments, including the finalT re [mean (SEM); 36.4 (0.2); 36.5 (0.3) and 36.5 (0.2)°C for the placebo, 100%-CHO and High-CHO tests, respectively]. During the 100%-CHO treatment, rates of carbohydrate oxidation were the highest and fat oxidation the lowest (P〈0.05), whereas the High-CHO treatment caused smaller changes. The results demonstrate that in the cold, enhancing energy substrate mobilization by ingesting substrates in the form of a supplement containing either mainly or only CHO does not cause detectable changes inM, heat loss,S or body temperatures, compared to the ingestion of a placebo. Under the present conditions, the results do not support the theory that energy substrate mobilization is a limiting factor for cold-induced thermogenesis in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00864222
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  • 2
    Electronic Resource
    Electronic Resource
    Forearm temperature profile during the transient phase of thermal stress (1992)
    Springer
    European journal of applied physiology 64 (1992), S. 395-401 
    Details
    ISSN: 1439-6327
    Keywords: Cold stress ; Cooling rate ; Intramuscular temperature ; Tissue temperature ; Transient response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The transient temperature response of the resting human forearm immersed in water at temperatures (T w) ranging from 15 to 36°C was investigated. Tissue temperature (T t) was continuously monitored by a calibrated multicouple probe during the 3-h immersions.T t was measured every 5 mm, from the longitudinal axis of the forearm to the skin surface. Skin temperature, rectal temperature, and blood flow ( $$\dot Q$$ ) were also measured during the immersions. The maximum rate of change of the forearm mean tissue temperature ( $$\dot T_{{\text{t, max}}}$$ ) occurred during the first 5 min of the immersion. $$\dot T_{{\text{t, max}}}$$ was linearly dependent onT w (P〈0.001), with mean values (SEM) ranging from −0.8 (0.1) °C · min−1 at 15°C to 0.2 (0.1) °C · min−1 at 36°C. The maximum rate of change of compartment mean temperature was dependent (P〈0.001) on the radial distance from the longitudinal axis of the forearm. The half-time for thermal steady state of the forearm mean tissue temperature was linearly dependent onT w between 30 and 36°C (P〈0.01), with mean values (SEM) ranging from 15.6 (0.6) min at 30°C to 9.7 (1.2) min at 36°C and not different between 15 and 30°C, averaging 16.2 (0.6) min. There was a significant linear relationship between the half-time for thermal steady-state of the compartment mean temperature and the radial distance from the longitudinal axis of the forearm for each value ofT w tested (P〈0.001). The data of the present study suggest that the forearm $$\dot Q$$ is an important determinant of the transient thermal response of the forearm tissue during thermal stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625057
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  • 3
    Electronic Resource
    Electronic Resource
    Factors limiting cold-water swimming distance while wearing personal floatation devices (2000)
    Springer
    European journal of applied physiology 82 (2000), S. 24-29 
    Details
    ISSN: 1439-6327
    Keywords: Key words Accidental immersion ; Adiposity ; Aerobic capacity ; Cooling rate ; Rectal temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of body adiposity, arm skinfold thickness, aerobic capacity, and cooling rate were studied in a mock survival swimming situation conducted in water at around 14 °C. Seventeen adult participants wore personal floatation devices on top of seasonal clothing and were asked to swim as far as they could, as if attempting to reach shore following an accidental immersion in cold water. Triceps and patellar skinfold thickness showed a significant correlation with distance covered (r=0.70 and 0.56, respectively), while abdominal skinfold and percent body fat showed no significant correlation. Maximum oxygen consumption (V˙O2max) was not significantly related to distance covered. There was a negative correlation between body cooling rate during the swimming period and distance covered. A multiple stepwise regression analysis, however, indicated that the only significant contributor to variance in the distance covered was the triceps skinfold thickness (r 2=0.49). It was concluded that for a healthy subject accidentally immersed in cold water, triceps skinfold thickness is a stronger predictor of the swimming distance covered than body adiposity, V˙O2max, or the drop in core temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050647
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  • 4
    Electronic Resource
    Electronic Resource
    Cyclic intramuscular temperature fluctuations in the human forearm during cold-water immersion (1991)
    Springer
    European journal of applied physiology 63 (1991), S. 188-193 
    Details
    ISSN: 1439-6327
    Keywords: Cold-induced vasodilatation ; Cold stress ; Tissue heat loss ; Tissue temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of the present study was to investigate the intramuscular temperature fluctuations in the human forearm immersed in water at 15°C. Tissue temperature (T t) was continuously monitored by a calibrated multi-couple probe during 3 h immersion of the forearm. The probe was implanted approximately 90 mm distal from the olecranon process along the ulnar ridge. T t was measured every 5 mm, from the longitudinal axis of the forearm (determined from computed tomography scanning) to the skin surface. Along with T t, rectal temperature, skin temperature and heat loss of the forearm were measured during the immersions. Five of the six subjects tested showed evidence of cyclic temperature fluctuations in the forearm limited to the muscle tissue. The first increase of the muscle temperature was observed 75 (SE 6) min after the onset of the immersion, and the duration of the cycle averaged 36 (SE 3) min. The maximum increase of the muscle temperature, which ranged between 0.4°C and 1.0°C, was measured at the axis of the forearm, and was inversely correlated to the circumference of the subject's forearm (P〈 0.05). No corresponding increases of the skin temperature and heat loss of the forearm were observed for the complete duration of the immersion. These data support the hypothesis of a significant contribution of the muscle vessels during cold-induced vasodilatation in the forearm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233846
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of postural changes on body temperatures and heat balance (1996)
    Springer
    European journal of applied physiology 72 (1996), S. 451-459 
    Details
    ISSN: 1439-6327
    Keywords: Posture ; Tilt-table ; Thermoneutrality ; Heat storage ; Blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Early studies have demonstrated that rectal temperature (T re) decreases and mean skin temperature (T sk) increases in subjects changing their posture from standing to supine, and vice versa. Such changes have important implications insofar as thermal stress experiments are conducted and interpreted. However, the extent of these changes between steady-state conditions is not known. In addition, it is not known whether thermal balance is also affected by postural changes. To examine these questions, 11 healthy males were exposed to a thermoneutral air environment (28.2–28.5°C and 40% relative humidity) in various postures at rest. Body temperatures, heat losses, and metabolic rate were measured. Subjects wore shorts only and began in an upright posture (standing or sitting at an inclination of 7.5°) on a customized tilt-table. They were tilted twice, once into a supine position and then back to the original upright position. Each tilt occurred after steady state was satisfied based on the subject's circadian variation of T re determined previously in a 4.25 h control supine trial. Times to supine steady state following the first tilt were [mean (SE)] 92.6 (6.4) and 116.6 (5.1) min for the standing and sitting trials, respectively. Times to upright steady state following the second tilt were 107.9 (11.4) and 124.1 (9.0) min. Mean steady-state T re and T sk were 36.87 (0.07) and 34.04 (0.14), 37.47 (0.09) and 33.48 (0.14), and 37.26 (0.05) and 33.49 (0.10) °C for supine, standing, and sitting, respectively. Thermal balance was attained in all steady-state conditions, and allowing for a decrease in the weighting factor of T re for mean body temperature in the upright postures, it also appears that thermal balance was preserved between changes in posture. These results are consistent with no perceived changes by the subjects in their thermal comfort and skin wetness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242275
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