Three case reports of the metabolic and electroencephalographic changes during advanced Buddhist meditation techniques.

To examine the extent to which advanced meditative practices might alter body metabolism and the electroencephalogram (EEG), we investigated three Tibetan Buddhist monks living in the Rumtek monastery in Sikkim, India. In a study carried out in February 1988, we found that during the practice of several different meditative practices, resting metabolism (VO2) could be both raised (up to 61%) and lowered (down to 64%). The reduction from rest is the largest ever reported. On the EEG, marked asymmetry in alpha and beta activity between the hemispheres and increased beta activity were present. From these three case reports, we conclude that advanced meditative practices may yield different alterations in metabolism (there are also forms of meditation that increase metabolism) and that the decreases in metabolism can be striking.

Comparison of the hunting reaction in normals and individuals with Raynaud's disease.

Cold-induced vasodilation (CIVD or hunting reaction) was studied in eight subjects with Raynaud's disease, an idiopathic vasospastic disorder of the peripheral vasculature, and in nine normal subjects using 5, 10, 15 +/- 1 degree C water bath immersions of the right middle finger. Differences between Raynaud's and normal subjects were only marginal at 5 degrees C; at 10 degrees C, Raynaud's subjects showed a longer time to the first rise of skin temperature, had lower mean digital skin temperature, and a lower amplitude of their digital skin temperature during CIVD; at 15 degrees C, Raynaud's subjects had a longer time to first rise, lower number of CIVD cycles, and a lower recovery temperature.

Metabolic and vasomotor insulative responses occurring on immersion in cold water.

Twenty male volunteers (17-28 yr of age) exhibiting a range of body weights (60 kg less than or equal to Wt less than or equal to 95 kg) and body fat (7% less than or equal to BF less than or equal to 23%) underwent total immersion while at rest in water between 36 and 20 degrees C. The metabolic heat production measured as a function of time and water temperature was converted to explicit linear functions of core (Tre) and mean skin (Tsk) temperature for each individual immersion. The metabolic functions defined planes of thermogenic activity that showed a fourfold steeper slope with respect to changes in Tsk for small lean subjects than for large fatter subjects. Small lean males also exhibited steeper slopes with respect to changes in Tre than heavier phenotypes. The time course of Tsk and Tre was simulated for each individual immersion with the aid of a time-dependent system of differential heat balance equations coupling different body compartments to the water bath. This formulation permitted the evaluation of internal and external conductances as a function of water temperature. Maximal internal insulation, indicating full vasoconstriction, was achieved at higher bath temperatures in small lean subjects than large fatter subjects. A decline in insulation is seen above a critical metabolic level (approximately 150 W) in small to average size subjects.

Auxiliary cooling: comparison of air-cooled vs. water-cooled vests in hot-dry and hot-wet environments.

Water-cooled, air-cooled, and ambient air-ventilated auxiliary cooling vests were evaluated in a hot-wet climate (HW) (35 degrees C, 75% R.H.) and a hot-dry environment (HD) with additional infrared radiation (Ta = 49 degrees C, 20% R.H., 68 degrees C black globe temperature). Twelve subjects dressed in full chemical warfare combat uniforms underwent 120 min of heat exposure in each combination of climate and cooling vest, except for the hot-dry environment and ambient-air vest. During each exposure, total exercise time was 20 min and rest time 100 min. This resulted in a mean time weighted metabolic rate of 180 W. Both water-cooled and air-cooled vests were sufficient for cooling in the HW climate: heat storage (delta S) was 13 and 7 W, final rectal temperature (Tre) 37.4 and 37.3 degrees C, and heart rate (HR) 124 and 112 b . min-1, respectively. While using the ambient-air vest, all variables were significantly (p less than 0.05) higher (delta S, 25 W; Tre, 37.7 degrees C; HR, 139 b . min-1; respectively). In the HD climate, both water and air-cooled vests were insufficient with a delta S of 46 and 48 W, final Tre of 38.4 and 38.3 degrees C, and final HR of 151 and 147 b . min-1. However, both cooling vests improved the subjects' physiological status compared to these predicted variables without auxiliary cooling. No significant differences were found between the air or the water-cooled vests in either the HD or HW climates. It was concluded that an air-cooled vest can be used with the same efficiency as a water-cooled vest. In contrast, the ambient-air vest was shown to have a low effectiveness in HW and to be dangerous in a HD climate.

Physiological responses of men and women to prolonged dry heat exposure.

Heat-acclimated men (n = 10) and women (n = 9) were exposed to hot-dry conditions (49 degrees C, 20% rh) for 4h to determine the effect of prolonged work in the heat on physiological differences between the sexes. Hourly exposures consisted of 10 min resting and 50 min walking at 1.34 m . s-1 (time-weighted metabolic rate = 175 and 151 W . m-2 for men and women, respectively). No significant difference in rectal temperature (Tre) was found between the sexes for each hour (h) of exposure. Heart rate (HR) of women, however, averaged 10-17 beats . min-1 higher than men. Mean skin temperature (Tsk) was also significantly higher in women throughout the exposure. For both sexes, the 4th-h Tre, HR, and Tsk were significantly higher than the preceding 3h. No sex related differences in total sweat rate (msw) or sweat sensitivity, as indicated by msw/delta Tre, were evident. It was concluded that: a) prolonged exposure to dry heat does not accentuate physiological differences between the sexes; b) women sweat at rates comparable to men over a 4-h period; c) 2-h acclimation sessions do not necessarily acclimate individuals for work of longer duration.

Sports medicine and the physiology of wheelchair marathon racing.

In the past three decades, wheelchair sports have become an international reality. Disabled athletes are exercising their right to accept the challenges and risks taken by able-bodied athletes. Marathon racing over a 26-mile, 385-yard course is the latest and most strenuous of the wheelchair athletic events. The small amount of available research data on wheelchair sports has been summarized, as well as some relevant data from exercise physiology studies on able-bodied subjects. Physicians and other health professionals who work with disabled people should be knowledgeable about the risks and benefits of wheelchair sports. Much more basic research is needed to improve the safety, training techniques, and performance of wheelchair athletes.

Persistence of impaired heat tolerance from artificially induced miliaria rubra.

Ten volunteers were heat acclimatized to 48.9 degrees C (Ta), 20% rh for 7 days to complete a 100-min walk on a level treadmill (1.56 m x s-1). Subjects were then divided into experimental (n = 6) and control (n = 4) groups. Miliaria rubra (heat rash) was then induced on the experimental subjects by wrapping them for 3 days in polyethylene plastic. All six developed marked miliaria with involvement of 40-70% of the total body surface area. All subjects were reexposed to walking in the heat on the 7th day after unwrapping, by which time rash was clinically indetectable, and again 14 days after unwrapping. On the first test (day 7) only one of the rashed group, and on the second test (day 14) only two could complete the 100-min walk; the control group finished without difficulty on both days. Body heat storage for the rash group was 2.5 times that of the control group on day 7 and 1.5 as great on day 14; measurements of mean body temperature (Tb) on the rash group indicated a much greater heat stress when compared to their own prerash-acclimatized values or those of the control group. These data demonstrate the potential of "healed" miliaria in the etiology of clinical heat illness.

Heat intolerance as a function of percent of body surface involved with miliaria rubra.

Twenty-four heat-acclimatized male volunteers were wrapped as previously described (Am. J. Physiol. 239 (Regulatory Integrative Comp. Physiol. 8): R226-R232, 1980) but to produce miliaria rubra (heat rash) in specific regions of the body. Three experimental rash groups were involved: 1) the torso (17% total skin surface rashed, n = 6), 2) torso and arms (38%, n = 8), or 3) legs (41%, n = 6), while four subjects served as controls. All subjects were reexposed to walking in the heat on the 7th day after unwrapping, and again 14, 21, and 28 days after unwrapping. When compared to responses for the last heat acclimatization day, tolerance time and sweat rate were lower and mean body temperature and delta heat storage significantly higher for experimental rash subjects contrasted to the controls for up to 21 days; however, no significant differences between the three rashed groups were found. The critical amount of surface area for heat intolerance from heat rash appears to be related to the specific region of the body and associated sweating responses; smaller rashed areas of the trunk, because they have greater potential for abundant sweating, may produce similar responses to heat stress as larger rashed areas of the limbs. Heat intolerance due to rash was not resolved until after 21 days.

Three instruments for assessment of WBGT and a comparison wiwh WGT (Botsball).

Environmental heat stress, expressed as the Wet Bulb Globe Temperature (WBGT), was measured outdoors using three different instruments: a) the conventional shaded dry-bulb, 15.2-cm black globe and naturally convected wet bulb thermometers, b) a minaturized thermometer kit, and c) a commercial WBGT instrument using a thermistor sensors. The WBGT values were compared with the Wet Globe Temperature (WGT) measured with a Botsball. Measurements were made visually on the instruments at regular intervals and an automated data collection system also was used to obtain data from thermocouples attached to the instruments. Statisticallly significant differences in WBGT readings were found among the instruments; however, the difference for a given environment usually was less than 0.5 degrees C. Readings taken by visual observations resulted in WBGT values which differed by less than 0.3 degrees C from those calculated from the automated data collection system. By using an equation derived for the Botsball, WBGT = 1.044 WGT - 0.187 (in degrees C), it is possible to convert the Botsball thermometer dial to indicate the conventional WBGT for outdoor environments, thus making it a simple instrument for assessing environmental heat stress at the work site.