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Biomedical subjects

N A Pimental

Publications and source records attributed to N A Pimental.

15 recordsLinked to original sources
PubMed1988

Portable, ambient air microclimate cooling in simulated desert and tropic conditions.

We examined the feasibility of providing ambient air during exercise and conditioned (cooled) air during rest on reducing physiological strain and optimizing tolerance time. Six male soldiers attempted 250-min exposures in hot/dry and hot/wet environments. Subjects wore chemical protective clothing over the combat vehicle crewman uniform and an air-cooled vest. They alternated between 50 min of treadmill walking (420 W) and 50 min of rest (105 W). During the walks, a backpack mounted blower provided a total of 10 or 18 cfm of air to the vest and face; while subjects received 18 cfm of conditioned air from an umbilical during rest. A control test with conditioned air during rest, but only a ventilated facepiece during work was also conducted in the hot/dry environment. In the hot/dry environment the ambient air backpack extended (p less than 0.05) tolerance time and significantly reduced rectal temperatures, heart rates and sweating rates compared to control; no differences were found between 10 and 18 cfm. In the hot/wet environment, tolerance time was extended compared to a predicted tolerance time assuming no microclimate cooling. We conclude that the ambient air backpack reduced physiological strain and improved tolerance time of combat vehicle crewmen during exercise in the heat.

Adult↗
PubMed1987

Effectiveness of an air-cooled vest using selected air temperature and humidity combinations.

We evaluated the effectiveness of an air-cooled vest in reducing thermal strain of subjects exercising in the heat (49 degrees C dry bulb (db), 20 degrees C dew point (dp] in chemical protective clothing. Four male subjects attempted 300-min heat exposures at two metabolic rates (175 and 315 W) with six cooling combinations--control (no vest) and five different db and dp combinations. Air supplied to the vest at 15 scfm ranged from 20-27 degrees C db, 7-18 degrees C dp; theoretical cooling capacities were 498-687 W. Without the vest, endurance times were 118 min (175 W) and 73 min (315 W). Endurance times with the vest were 300 min (175 W) and 242-300 min (315 W). The five cooling combinations were similarly effective in reducing thermal strain and extending endurance time, although there was a trend for the vest to be more effective when supplied with air at the lower dry bulb temperature. At 175 W, subjects maintained a constant body temperature; at 315 W, the vest's ability to extend endurance is limited to about 5 hours.

Adult↗
PubMed1985

Anthropometric changes at high altitude.

Eight white males (18-25 yr) were evaluated before, during and after 18-d residence on the summit of Pikes Peak, CO (4300 m; high altitude, HA) to describe the anthropometric changes associated with weight loss and to test the accuracy of a number of previously published prediction equations in assessing any alteration of the relative fat-to-lean tissue ratio during exposure to HA. Body weight (BW), 10 circumference (C), and 7 skinfold (SF) measurements were obtained preprandial at sea level (SL) and on days 2,4,6,9,12,16, and 18 at HA. Body density was estimated by hydrostatic weighing (HW) pre- and post-HA. BW differed from SL (p less than 0.01) after day 9 at HA. HW indicated that the pre- to post-HA weight loss was partitioned into a 2.06 kg loss in fat-free body mass (p less than 0.001) and an insignificant increase in fat wt (0.58 kg). Percent body fat (BF) increased from 16.6 to 17.7 (p less than 0.02). After day 9 of HA, the sum of SF and C measurements increased (p less than 0.02) and decreased (p less than 0.05) from SL, respectively. The largest changes occurred in the chest and scapula SF and in the C of the hip, neck, calf, and two abdominal sites. The alterations in triceps, waist, and total SF were related to the increase in fat weight and BF (r greater than 0.71).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Thermoregulatory responses to upper body exercise.

The purpose of this study was to compare thermoregulatory responses between upper body and lower body exercise. Nine male subjects performed 60 min of arm crank (AC) and cycle (CY) exercise at the same absolute intensity (oxygen uptake = 1.61 X min-1) and at the same relative intensity (60% of ergometer specific peak oxygen uptake) in a temperate (24 degrees C, 20% rh) environment. During the absolute intensity experiments, rectal temperature and sweating rate responses were essentially the same for both modes of exercise. In addition, no differences were found for chest, back, arm, or thigh skin temperatures, but calf skin temperature was significantly (P less than 0.05) lower during arm crank than cycle exercise. During the relative intensity experiments, thermoregulatory responses were lower during arm crank than cycle exercise. In addition, we found no difference between esophageal and rectal temperature values elicited by arm crank exercise. These results indicate that the examined thermoregulatory responses are independent of the skeletal muscle mass employed and dependent upon the absolute metabolic intensity.

Adult↗
PubMed1984

Differential ratings of perceived exertion and various physiological responses during prolonged upper and lower body exercise.

This study examined whether prolonged exercise employing upper or lower body muscle groups led to significant alterations in three differentiated ratings of perceived exertion (RPE). Multiple regression analyses were used to identify those physiological responses which accounted for the greatest variability in these three RPE. Nine volunteer males performed 60 min of arm crank and cycle exercise at similar absolute and at similar relative exercise intensities. There were no significant differences (P greater than 0.05) between arm and leg exercise for oxygen uptake (VO2) during the absolute tests (approximately 1.60 1 . min-1) or during the relative tests (approximately 60% peak VO2). The RPE included local RPE (muscle and joint exertion), central RPE (ventilatory and circulatory exertion), and overall RPE. During the absolute tests, the final means for all three RPE were lower (P less than 0.05) for leg than arm exercise. No differences (P greater than 0.05) were found during the relative tests between arm and leg exercise for any of the three RPE. Local RPE was generally higher than central RPE. The various physiological responses accounted for more (total) variance in all three RPE for arm than leg exercise (absolute and relative arm exercise: median R2 = 0.99; absolute and relative leg exercise: median R2 = 0.75). Lactate and the ventilatory equivalent of oxygen made the greatest contribution to R2. These data suggest that RPE may be more closely related to relative exercise intensity, and perceptual cues may be more readily monitored from smaller muscle masses such as the upper body. Further, steady-state RPE was not attained during prolonged upper body exercise.

Adult↗
PubMed1984

Hydration and vascular fluid shifts during exercise in the heat.

This study examined the effects of hypohydration on plasma volume and red cell volume during rest in a comfortable (20 degrees C, 40% relative humidity) and exercise in a hot-dry (49 degrees C, 20% relative humidity) environment. A group of six male and six female volunteers [matched for maximal O2 uptake (VO2 max)] completed two test sessions following a 10-day heat acclimation program. One test session was completed when subjects were euhydrated and the other when subjects were hypohydrated (-5% from base-line body wt). The test sessions consisted of rest for 30 min in a 20 degrees C antechamber, followed by two 25-min bouts of treadmill walking (approximately 30% of VO2 max) in the heat, interspersed by 10 min of rest. No significant differences were found between the genders for the examined variables. At rest, hypohydration elicited a 5% decrease in plasma volume with less than 1% change in red cell volume. During exercise, plasma volume increased by 4% when subjects were euhydrated and decreased by 4% when subjects were hypohydrated. These percent changes in plasma volume values were significantly (P less than 0.01) different between the euhydration and hypohydration tests. Although red cell volume remained fairly constant during the euhydration test, these values were significantly (P less than 0.01) lower when hypohydrated during exercise. We conclude that hydration level alters vascular fluid shifts during exercise in a hot environment; hemodilution occurs when euhydrated and hemoconcentration when hypohydrated during light intensity exercise for this group of fit men and women.

Adult↗
PubMed1984

Physiological responses to prolonged upper-body exercise.

To date, investigators have not examined physiological responses to prolonged upper-body exercise. Knowledge of the feasibility of performing this type of exercise and the elicited responses could have application in designing continuous training programs for upper-body muscle groups. Nine males, with a peak oxygen uptake (means +/- SD) of 49 +/- 7 for cycle (CY) and 35 +/- 6 ml X min-1 X kg-1 for arm crank (AC) exercise, completed four 60-min exercise tests. The subjects performed AC and CY exercise at the same absolute (ABS) oxygen uptake (1.6 1 X min-1) and at the same relative (REL) percent of ergometer-specific peak oxygen uptake (60%). During the ABS tests, AC exercise elicited significantly (P less than 0.05) greater heart rate (HR), ventilatory equivalent of oxygen (VE X VO2(-1), blood lactate (La), and percent decrease in plasma volume (PV) than CY exercise. During the REL tests, HR was lower and VE X VO2(-1) was higher for AC than CY exercise; there were no differences between AC and CY exercise in La or PV responses. These data demonstrate that upper-body exercise can be performed for 60 min at a relative intensity which might be sufficient to elicit a cardiovascular training effect. However, because heart rates are lower during upper-than lower-body exercise at the same relative intensity, exercise prescriptions based on heart rate alone may need to be modified for upper-body exercise.

Adult↗
PubMed1983

Determination of maximal aerobic power during upper-body exercise.

The purpose of this investigation was to evaluate four protocols for their effectiveness in eliciting maximal aerobic power (peak VO2) during arm-crank exercise. Comparisons were made 1) between a continuous (CON) and an intermittent (INT) protocol (both employed a crank rate of 50 rpm) and 2) among the CON protocols employing crank rates of 30, 50, or 70 rpm. For the first group of experiments no significant (P greater than 0.05) differences were found between the CON and INT protocols for peak VO2, maximal pulmonary ventilation (VEmax), maximal heart rate (HRmax), or maximal blood lactate (LAmax) responses. For the second group of experiments, the CON-50 was compared with the CON-30 and CON-70 protocols. In comparison to the CON-50, significantly higher peak VO2 (+10%) and VEmax (+14%) responses were elicited by the CON-70 protocol, whereas significantly lower peak VO2 (-11%), VEmax (-23%), HRmax (-8%), and LAmax (-29%) responses were elicited by the CON-30 protocol. Of the arm-crank protocols examined the combination of a continuous design and a crank rate of 70 rpm provided the most effective protocol to elicit peak VO2 values.

Adult↗
PubMed1980

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.

Acclimatization↗