Thermoregulation during rest and exercise in different postures in a hot humid environment

1980 ◽  
Vol 48 (6) ◽  
pp. 999-1007 ◽  
Author(s):  
K. Kabayashi ◽  
S. M. Horvath ◽  
F. J. Diaz ◽  
D. R. Bransford ◽  
B. L. Drinkwater
Keyword(s):  
Time Course ◽  
Work Load ◽  
Skin Surface ◽  
Bicycle Ergometer ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Humid Environment ◽  
Supine Posture ◽  
Three Body ◽  
Rest And Exercise

The time course of whole-body sweating and thermal regulation during rest and exercise in a hot humid environment was investigated in three body postures. After 45 min rest in the upright, low-sit, or supine posture, five unacclimatized men exercised for 45 min on a bicycle ergometer in the same posture in an environment of 49.5 degrees C, 28.9 Torr. Exercise was performed at two different work loads, corresponding to about 30 and 45% of VO2max. During exercise auditory canal temperature, rectal temperature, and mean skin temperature increased linearly being highest in the supine and lowest in the upright posture. Percentage of evaporated sweat from the skin to secreted sweat was 65% in upright, 52% in the low-sit, and only 46% in the supine posture during the last 20 min of exercise regardless of work load. The time course of the rate of body heat storage was different from predictions based on the thermal balance equation. Evaporative heat loss was not 100% effective in cooling the skin surface.

Effect of physical training on exercise-induced sweating in women

1981 ◽  
Vol 51 (6) ◽  
pp. 1526-1532 ◽  
Author(s):  
T. Araki ◽  
K. Matsushita ◽  
K. Umeno ◽  
A. Tsujino ◽  
Y. Toda
Keyword(s):  
Physical Training ◽  
Time Course ◽  
Sweat Rate ◽  
Work Load ◽  
Young Female ◽  
Bicycle Ergometer ◽  
Progressive Decrease ◽  
Trained Group ◽  
Hot Environment ◽  
Exercise Induced

The effect of physical training on the time course of sweat rate in women has been examined. Physically untrained and trained young female subjects pedaled a bicycle ergometer at work rates of 483 and 981 kgm.min-1, for 2 h in summer and winter in an ambient environment of 30 degrees C db and 60% rh. The trained women also worked at 1,070 kgm.min-1 and the untrained at 391 kgm.min-1. Rectal temperature was measured, and capsule sweat samples were collected from the back every 5 min. Sweating was initiated more rapidly in the trained group than in the untrained group. The trained group working at a load of 981 kgm.min-1 exhibited a progressive decrease in sweat rate. This was not observed at a work load of 483 kgm.min-1. Hidromeiosis was rarely seen in the untrained group. However, in the untrained women who underwent 60 days of physical training, initiation of sweating occurred more quickly and hidromeiosis was observed. It was concluded that previous physical training improved women's capacity for useful sweating during exercise in a hot environment.

Plasma volume changes during rest and exercise in different postures in a hot humid environment

1979 ◽  
Vol 47 (4) ◽  
pp. 798-803 ◽  
Author(s):  
F. J. Diaz ◽  
D. R. Bransford ◽  
K. Kobayashi ◽  
S. M. Horvath ◽  
R. G. McMurray
Keyword(s):  
Plasma Volume ◽  
Control Period ◽  
Weight Losses ◽  
Humid Environment ◽  
Supine Posture ◽  
Cool Environment ◽  
Exercise Period ◽  
Zero Reference ◽  
Plasma Volume Shifts ◽  
Rest And Exercise

Plasma volume shifts were investigated in five male subjects who rested and exercised in the upright, low-sit, and supine postures in a hot humid environment (49.5 degrees C, 28.9 Torr). The resting and exercise periods were each 45 min in duration. Weight losses during rest were 0.3% with an additional weight loss of 1.1% during exercise. During exercise subjects worked at either 360 or 540 kpm.min-1 in each of three postures. Each experiment was preceded by a 30-min control period in the supine posture at an ambient temperature of 22 degrees C. At rest plasma volume was reduced 17.3% in the upright, 9.0% in the low-sit, and 2.2% in the supine postures (using the end of the supine rest as the zero reference point). Supine exercise resulted in a plasma volume decrease of 11%, the low-sit 7.1%, and the upright 2.7%. The total reduction in plasma volume during the rest and exercise period was 20% in the upright, 16.1% in the low-sit, and 13.3% in the supine. No significant differences in plasma volume shifts were observed between the high and low work loads. The results indicate that the plasma volume shifts observed during rest and exercise in the heat are qualitatively similar to those observed in a cool environment.

The Effects of Whole Body Exercise on Choice-Reaction Time Performance

1974 ◽  
Vol 18 (4) ◽  
pp. 476-479
Author(s):  
Alan B. Dechovitz ◽  
Rodney K. Schutz ◽  
Thomas L. Sadosky
Keyword(s):  
Reaction Time ◽  
Physical Exercise ◽  
Cognitive Performance ◽  
Choice Reaction Time ◽  
Error Rate ◽  
Reaction Time Task ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Practical Significance ◽  
Whole Body

A study which investigates how cognitive performance is affected by simultaneous, physical exercise is reported. Whole body exercise on a bicycle ergometer at four work loads (30, 60, 120 and 180 watts) and four rates (30, 40, 60 and 90 rpm) for durations of from 5 to 25 minutes were investigated. A two-stage choice reaction time task was performed at one minute intervals prior to, during and after exercise. Psychomotor performance was measured by reaction time and error rate. Although the subjects were fully trained, very pronounced subject differences were noted. The psychomotor response did not vary with work load (watts) or work rate (rpm), and in addition, was not related to the physiological measurements recorded for heart rate and oxygen consumption. Nominal differences in reaction time and error rate were detected during and after exercise; but it was concluded that physical exercise, even if strenuous, does not cause a modification in cognitive performance of practical significance.

Respiratory quotient during exercise

1961 ◽  
Vol 16 (4) ◽  
pp. 606-610 ◽  
Author(s):  
B. Issekutz ◽  
K. Rodahl
Keyword(s):  
Time Course ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Minute Volume ◽  
Initial Increase ◽  
Maximal Aerobic Capacity ◽  
Co2 Output ◽  
Straight Line ◽  
Heavy Work ◽  
Secondary Drop

O2 uptake and CO2 output were determined during exercise on the bicycle ergometer. During moderate and heavy work three phases could be distinguished in the time course of RQ: a) initial increase, b) secondary drop followed by c) a continuous rise to a steady state which was reached after 3 ½12—4 min work. The rise of work RQ (ΔRQ) above an assumed metabolic RQ of 0.75 (or 0.83) showed an approximately logarithmic increase as work load increased. In the same subject there was a straight-line correlation between “nonmetabolic” excess CO2 (= total CO2 minus 0.75 x O2) and the increase of blood lactate level ( P < 0.001). In pooled calculations, a correlation coefficient γ = 0.92 was found. Whereas the respiratory minute volume plotted against O2 uptake or CO2 output showed a relative hyperventilation as the subject approached maximal aerobic capacity, excess CO2 increased with the ventilation in a straight-line fashion. It was concluded that the δRQ represents the percentual participation of anaerobic glycolysis in the total energy expenditure rather than the fuel used during exercise. Submitted on January 26, 1961

Catecholamine-fuel interrelationships during exercise in fasting men

1980 ◽  
Vol 48 (1) ◽  
pp. 109-113 ◽  
Author(s):  
J. M. Pequignot ◽  
L. Peyrin ◽  
G. Peres
Keyword(s):  
Maximal Oxygen Consumption ◽  
Plasma Catecholamines ◽  
Plasma Free Fatty Acid ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Plasma Norepinephrine ◽  
Plasma Catecholamine ◽  
Adrenergic Response ◽  
Response To Exercise

Adrenergic response to exercise and the relationships between plasma catecholamines and blood energetic substrates were studied in sedentary men after 15 h of fasting. Subjects pedaled a bicycle ergometer until exhaustion at a work load approximating 80% maximal oxygen consumption. Working ability was diminished by the fast (P less than 0.025). Resting plasma norepinephrine level was increased by fasting. During exercise plasma epinephrine (E) and norepinephrine (NE) concentrations were more elevated in fasting subjects than in fed subjects. Plasma catecholamine (CA) levels in fasting men correlated with blood glucose, blood lactate, and plasma glycerol concentrations. There was no significative correlation between CA and plasma free fatty acid (FFA) levels. The increased adrenergic activity in fasting subjects correlated with reduced endurance time. This study emphasizes the role of CA release, probably combined with other hormonal factors, in the mobilization of energy substrates during submaximal exercise.

Time course of insulin resistance associated with feeding dogs a high-fat diet

1997 ◽  
Vol 272 (1) ◽  
pp. E147-E154 ◽  
Author(s):  
A. P. Rocchini ◽  
P. Marker ◽  
T. Cervenka
Keyword(s):  
Insulin Resistance ◽  
Blood Pressure ◽  
Glucose Uptake ◽  
Dose Response ◽  
High Fat Diet ◽  
Time Course ◽  
Rapid Development ◽  
Diet Group ◽  
Whole Body ◽  
High Fat

The current study evaluated both the time course of insulin resistance associated with feeding dogs a high-fat diet and the relationship between the development of insulin resistance and the increase in blood pressure that also occurs. Twelve adult mongrel dogs were chronically instrumented and randomly assigned to either a control diet group (n = 4) or a high-fat diet group (n = 8). Insulin resistance was assessed by a weekly, single-dose (2 mU.kg-1.min-1) euglycemic-hyperinsulinemic clamp on all dogs. Feeding dogs a high-fat diet was associated with a 3.7 +/- 0.5 kg increase in body weight, a 20 +/- 4 mmHg increase in mean blood pressure, a reduction in insulin-mediated glucose uptake [(in mumol-kg-1.min-1) decreasing from 72 +/- 6 before to 49 +/- 7 at 1 wk, 29 +/- 3 at 3 wk, and 30 +/- 2 at 6 wk of the high-fat diet, P < 0.01]. and a reduced insulin-mediated increase in cardiac output. In eight dogs (4 high fat and 4 control), the dose-response relationship of insulin-induced glucose uptake also was studied. The whole body glucose uptake dose-response curve was shifted to the right, and the rate of maximal whole body glucose uptake was significantly decreased (P < 0.001). Finally, we observed a direct relationship between the high-fat diet-induced weekly increase in mean arterial pressure and the degree to which insulin resistance developed. In summary, the current study documents that feeding dogs a high-fat diet causes the rapid development of insulin resistance that is the result of both a reduced sensitivity and a reduced responsiveness to insulin.

Tuning of a Basic Coordination Pattern Constructs Straight-Ahead and Curved Walking in Humans

2004 ◽  
Vol 91 (4) ◽  
pp. 1524-1535 ◽  
Author(s):  
Grégoire Courtine ◽  
Marco Schieppati
Keyword(s):  
Principal Components ◽  
Lower Limb ◽  
Time Course ◽  
Body Movement ◽  
The Body ◽  
Whole Body ◽  
Coordination Pattern ◽  
Data Set ◽  
Coordination Patterns ◽  
Straight Ahead

We tested the hypothesis that common principles govern the production of the locomotor patterns for both straight-ahead and curved walking. Whole body movement recordings showed that continuous curved walking implies substantial, limb-specific changes in numerous gait descriptors. Principal component analysis (PCA) was used to uncover the spatiotemporal structure of coordination among lower limb segments. PCA revealed that the same kinematic law accounted for the coordination among lower limb segments during both straight-ahead and curved walking, in both the frontal and sagittal planes: turn-related changes in the complex behavior of the inner and outer limbs were captured in limb-specific adaptive tuning of coordination patterns. PCA was also performed on a data set including all elevation angles of limb segments and trunk, thus encompassing 13 degrees of freedom. The results showed that both straight-ahead and curved walking were low dimensional, given that 3 principal components accounted for more than 90% of data variance. Furthermore, the time course of the principal components was unchanged by curved walking, thereby indicating invariant coordination patterns among all body segments during straight-ahead and curved walking. Nevertheless, limb- and turn-dependent tuning of the coordination patterns encoded the adaptations of the limb kinematics to the actual direction of the walking body. Absence of vision had no significant effect on the intersegmental coordination during either straight-ahead or curved walking. Our findings indicate that kinematic laws, probably emerging from the interaction of spinal neural networks and mechanical oscillators, subserve the production of both straight-ahead and curved walking. During locomotion, the descending command tunes basic spinal networks so as to produce the changes in amplitude and phase relationships of the spinal output, sufficient to achieve the body turn.

Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura

1999 ◽  
Vol 202 (21) ◽  
pp. 3021-3028 ◽  
Author(s):  
T.C. Hoffman ◽  
G.E. Walsberg
Keyword(s):  
Skin Surface ◽  
The Body ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Zenaida Macroura ◽  
Ambient Temperatures ◽  
Rapid Adjustment ◽  
Mourning Doves ◽  
A Minor ◽  
Cutaneous Evaporation

We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 degrees C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 degrees C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand.

Use of respiratory quotients in assessment of aerobic work capacity

1962 ◽  
Vol 17 (1) ◽  
pp. 47-50 ◽  
Author(s):  
B. Issekutz ◽  
N. C. Birkhead ◽  
K. Rodahl
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Work Load ◽  
Work Capacity ◽  
Bicycle Ergometer ◽  
Carbon Dioxide Output ◽  
Ergometer Test ◽  
Aerobic Work Capacity ◽  
Bicycle Ergometer Test ◽  
Better Than

Oxygen uptake and carbon dioxide output were measured in 32 untrained subjects during exercise on the bicycle ergometer. It was shown that the work respiratory quotient (RQ) under standardized conditions can be used as a measure of physical fitness. ΔRQ (work RQ minus 0.75) increases logarithmically with the work load and maximal O2 uptake is reached at a ΔRQ value of 0.40. This observation offered the possibility of predicting the maximal O2 uptake of a person, based on the measurement of RQ during a single bicycle ergometer test at a submaximal load. For each work RQ between 0.95 and 1.15 a factor was presented, together with the aid of a simple equation, which gave a good approximation (generally better than ±10%) of the maximal O2 uptake.

scholarly journals Event-related potentials following exercise bouts of different intensity

2007 ◽  
Vol 60 (11-12) ◽  
pp. 531-535 ◽  
Author(s):  
Otto Barak ◽  
Vesna Ivetic ◽  
Danka Filipovic ◽  
Nada Naumovic ◽  
Damir Lukac ◽  
...  
Keyword(s):  
Physical Activity ◽  
Positive Impact ◽  
Event Related Potentials ◽  
Bicycle Ergometer ◽  
Whole Body ◽  
Functional Diagnostics ◽  
Ergometer Exercise ◽  
Related Potentials ◽  
The Impact ◽  
Bicycle Ergometer Exercise

Introduction. A number of articles on physical activity analyze the effects of acute bouts of physical exercise on the whole body. These experiments mainly include questionnaires and measurements of reaction time. The use of event-related potentials in laboratories for functional diagnostics is only of recent date. The aim of this experiment was to give insights into the impact of physical activity of different intensity on the amplitude and latency of P300 cognitive potentials. Material and methods. After recording cognitive event-related potentials in 17 young (21.6?1.07 yrs) healthy adults (at Fz and Cz), the participants underwent a controlled bicycle ergometer exercise. Each exercise lasted 10 minutes, with successive increase in the intensity to 60%, 75% and 90% of the maximum pulse rate and maintaining this level of intensity for six minutes. Immediately after each bout of exercise, event-related potentials were recorded. Results. The amplitude of the P300 wave, following exercise intensity at 75% of the maximum pulse (Pmax) (Fz 15.00?4.57; Cz 18.63?8.83 mV) was statistically higher (p<0.05) than the amplitude of the P300 at rest (Fz 11.21?4.15 mV; Cz 13.40?8.04 mV), at 60% (Fz 11.86?5.11 mV; Cz 14.54?8.06 mV) and at 90% of maximum pulse (Fz 13.26?4.73 mV; Cz 14.91?8.91 mV). There were no statistically significant differences (p>0.05) between amplitudes at 60% of Pmax and values obtained at rest and at 90% of Pmax. Also, no statistically significant differences were recorded (p>0.05) among the latencies of P300 recorded at rest (Fz 323.57?13.24 ms; Cz 323.57?13.24 ms) and at 60% of Pmax (Fz 321.14?22.38 ms; Cz 321.86?22.88 ms), at 75% of Pmax (Fz 321.50?16.67 ms; Cz 322.50?14.60 ms) and at 90% of Pmax (Fz 326.29?7.85 ms; Cz 325.43?7.63 ms). Discusssion and Conclusion. Physical activity has a positive impact on cognitive functions. At intermediate intensities, the amplitude of P300 increases, but at submaximal intensities it decreases to values obtained at rest. However, the latency of P300 did not show a statistically significant change after different intensities of exercise.

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