2007, Piran, Slovenia
2007, Piran, Slovenia 2007, Piran, Slovenia
Environmental Ergonomics XII Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007 similarly, HR was 132.5±10.3 and 133.8±10.8 beats per min for menthol and control condition, respectively (p=0.9). Despite similar Tre at rest and during the first 15 min of cycling in the two conditions, during the last 10 min of exercise the rate of rise was higher in menthol condition (Table 1). Accordingly, the time to reach Tre of 38 oC was shorter when cycling with menthol than without menthol application (Table 1). The proximal-distal skin temperature gradient, which is considered a vasoconstriction index, was higher in menthol condition only in the first 12 min of exercise (Fig. 1). In addition, VO2 was higher in the same exercise period in menthol condition (Table 1) without being different from this time and onwards. DISCUSSION Upon exercise initiation, previously applied menthol on the skin seems to induce vasoconstriction and enhance thermogenesis that results in a faster rectal temperature rise, which, in the late state of exercise, counteracts the vasoconstrictive effect of menthol. REFERENCES Hensel, H., Zotterman, Y., 1951. The effect of menthol on the thermoreceptors . Acta. Physiol. Scand. 24: 27-34. Schafer, K., Braun, A., Isenberg, C. 1986. Effect of menthol on cold receptor activity. J. Gen. Physiol. 88:757-776. 326 ΔΤ (Τsk-diff o C) 4,5 4 3,5 3 2,5 2 1,5 1 0,5 0 § R 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 Time (min) Menthol Control Fig 1. Changes in forearm-fingertip difference (ΔTsk-diff), during 30 min of cycling with (Menthol), or without (Control) menthol application. (§): Differences between conditions p
Cold physiology COGNITIVE PERFORMANCE IS ENHANCED DURING COLD- WATER IMMERSION AND EXERCISE John W. Castellani, Ingrid V. Sils, Myra Reese, and Catherine O’Brien Thermal and Mountain Medicine Division U.S. Army Research Institute of Environmental Medicine Natick, Massachusetts 01760 USA Contact person: john.castellani@us.army.mil INTRODUCTION Studies suggest that cognitive performance degrades as core temperature falls during resting studies. However, it is unknown how the rate of cooling affects cognitive performance at a specific core temperature. The purpose of this study was to determine if the rate of core temperature cooling affects cognitive function. We hypothesized that cognitive function would be impaired to a greater degree during cold-water immersion when the rate of rectal temperature (Tre) cooling was slower compared to trials where core temperature fell faster. METHODS Ten men (20 ± 2 yr, 178 ± 7 cm height, 73.4 ± 7.1 kg body weight, VO2peak, 47.2 ± 4.8 ml·kg - 1 ·min -1 , and 15.5 ± 3.9 % body fat) completed 8 different, randomized, trials (which varied in the rate of cooling) in either 10 or 15°C water, in either chest (C) or waist (W) deep water while walking at either 0.44 or 0.88 m·s -1 . Subjects also completed a control trial where they were not immersed. Cognitive function was measured using standard performance tests: 4choice reaction time, match-to-sample, visual vigilance, grammatical reasoning, and symbol substitution. Tests were conducted before immersion and during immersion when Tre reached 36.5°C or 2 hours had elapsed. Significance was set at p < 0.05. Data are presented as mean ± SD. Visual Vigilance. This test of visual vigilance was designed to resemble military tasks requiring sustained scanning of the visual environment for infrequent, difficult to detect stimuli such as those during sentry duty. The task required the participant to detect a small, faint stimulus that randomly appeared for a second at various locations on the computer screen On the average, presentation of a stimulus occurred once a minute. The participant was told to respond as quickly as possible when a stimulus was detected. Dependent measures included correct detections and the response time. Responses made before (or after) stimulus occurrence were recorded as false alarms. The duration of this test was 20 minutes. Four-Choice Visual Reaction Time. Volunteers were presented with a series of visual stimuli at one of four different spatial locations on the computer screen. The volunteer's task was to indicate the correct spatial location of each stimulus by striking one of four corresponding keys on the computer keyboard. Dependent measures included the response latency for each trial, premature errors (responding before the presentation of the stimulus), errors of omission (response latency >1 sec) and errors of commission (hitting the wrong key). The duration of this test was approximately 5 minutes. Delayed Match-to-Sample. This is a subtest of the Walter Reed Performance Assessment Battery. During this test, a sample pattern of 36 red and green grid squares was presented on the computer display. The volunteer studied this pattern and then pressed a key on the keyboard. The sample pattern disappeared and the screen was blank for either 8 or 16 seconds ("delay"). Next, two patterns were presented and the volunteer selected the pattern 327
- Page 275 and 276: Sweating Such differences could be
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Environmental Ergonomics XII<br />
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana <strong>2007</strong><br />
similarly, HR was 132.5±10.3 and 133.8±10.8 beats per min for menthol and control<br />
condition, respectively (p=0.9). Despite similar Tre at rest and during the first 15 min of<br />
cycling in the two conditions, during the last 10 min of exercise the rate of rise was higher in<br />
menthol condition (Table 1). Accordingly, the time to reach Tre of 38 oC was shorter when<br />
cycling with menthol than without menthol application (Table 1).<br />
The proximal-distal skin temperature gradient, which is considered a vasoconstriction index,<br />
was higher in menthol condition only in the first 12 min of exercise (Fig. 1). In addition, VO2<br />
was higher in the same exercise period in menthol condition (Table 1) without being different<br />
from this time and onwards.<br />
DISCUSSION<br />
Upon exercise initiation, previously applied menthol on the skin seems to induce<br />
vasoconstriction and enhance thermogenesis that results in a faster rectal temperature rise,<br />
which, in the late state of exercise, counteracts the vasoconstrictive effect of menthol.<br />
REFERENCES<br />
Hensel, H., Zotterman, Y., 1951. The effect of menthol on the thermoreceptors . Acta.<br />
Physiol. Scand. 24: 27-34.<br />
Schafer, K., Braun, A., Isenberg, C. 1986. Effect of menthol on cold receptor activity. J. Gen.<br />
Physiol. 88:757-776.<br />
326<br />
ΔΤ (Τsk-diff o C)<br />
4,5<br />
4<br />
3,5<br />
3<br />
2,5<br />
2<br />
1,5<br />
1<br />
0,5<br />
0<br />
§<br />
R 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29<br />
Time (min)<br />
Menthol<br />
Control<br />
Fig 1. Changes in forearm-fingertip difference (ΔTsk-diff), during 30 min of<br />
cycling with (Menthol), or without (Control) menthol application. (§): Differences<br />
between conditions p
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