Exercise hyperpnea and hyperthermia in humans

1996 ◽  
Vol 81 (3) ◽  
pp. 1249-1254 ◽  
Author(s):  
M. D. White ◽  
M. Cabanac
Keyword(s):  
Work Capacity ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Brain Cooling ◽  
Supportive Evidence ◽  
Climatic Chamber ◽  
Selective Brain Cooling ◽  
Temperature Thresholds ◽  
Exercise Hyperpnea ◽  
Male Subjects

The problem of the relative hyperpnea occurring at high levels of exercise remains unresolved. This study examined whether the hyperpnea observed in humans during exercise at approximately 70% of maximal work capacity was related to cranial (tympanic) and thoracic (esophageal) temperatures. Six trained male subjects pedaled at approximately 60 revolutions/min on an electrically braked cycle ergometer in a climatic chamber at 25 degrees C and approximately 35% relative humidity in two sessions. The subjects pedaled until exhaustion in two sessions. In one session work rate was increased by 40 W every 2 min and in the other session by 20 W every 2 min. In both exercise sessions, core temperature thresholds for ventilation were evident and subsequently tympanic and esophageal temperatures diverged. This suggested that the hyperpnea in humans observed after approximately 70% of an individual's maximal work rate was determined, in part, by core temperatures and revealed supportive evidence for selective brain cooling in humans.

Panting in reindeer (Rangifer tarandus)

2000 ◽  
Vol 279 (4) ◽  
pp. R1190-R1195 ◽  
Author(s):  
Øyvind Aas-Hansen ◽  
Lars P. Folkow ◽  
Arnoldus Schytte Blix
Keyword(s):  
Heat Load ◽  
Rangifer Tarandus ◽  
Minute Volume ◽  
Respiratory Frequency ◽  
Brain Cooling ◽  
Climatic Chamber ◽  
Selective Brain Cooling ◽  
Open Mouth ◽  
Rangifer Tarandus Tarandus ◽  
Air Temperatures

Two winter-insulated Norwegian reindeer ( Rangifer tarandus tarandus) were exposed to air temperatures of 10, 20, 30, and 38°C while standing at rest in a climatic chamber. The direction of airflow through nose and mouth, and the total and the nasal minute volumes, respectively, were determined during both closed- and open-mouth panting. The animals alternated between closed- and open-mouth panting, but the proportion of open-mouth panting increased with increasing heat load. The shifts from closed- to open-mouth panting were abrupt and always associated with a rise in respiratory frequency and respiratory minute volume. During open-mouth panting, the direction of airflow was bidirectional in both nose and mouth, but only 2.4 ± (SD) 1.1% of the air was routed through the nose. Estimates suggest that the potential for selective brain cooling is markedly reduced during open-mouth panting in reindeer as a consequence of this airflow pattern.

Selective brain cooling is affected by wearing headgear during exercise

1993 ◽  
Vol 74 (3) ◽  
pp. 1229-1233 ◽  
Author(s):  
W. Rasch ◽  
M. Cabanac
Keyword(s):  
Heat Loss ◽  
Cycle Ergometer ◽  
Tympanic Temperature ◽  
Esophageal Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Exercise Load ◽  
Convective Heat Loss ◽  
The Face ◽  
Skin Temperatures

The purpose of this work is to relate the concept of selective brain cooling (SBC) during exercise to heat loss from the head while either bare or covered. During hyperthermia, SBC is considered to occur if tympanic temperature (Tty) is lower than esophageal temperature (Tes). In experiment I the head heat loss was measured with and without headgear. Each of four subjects took part in three sessions of exercise on a cycle ergometer. The face was cooled to simulate outdoor conditions. The first session (no headgear) served as control for the two following sessions in which a headband and a woolen cap were worn. Evaporative and radiative-convective heat loss were monitored from the head. Wearing a cap significantly reduced the heat loss from the head compared with the control condition. During the headband session the heat loss was not significantly lower than the control values. Tty, Tes, and head skin temperatures (T(sk)) were also recorded. Tty was significantly lower (-0.55 +/- 0.15 degrees C) than Tes at the end of exercise (150-W exercise load) when no headgear was worn. During headgear sessions, Tty was no longer significantly lower than Tes, either during the headband (-0.15 +/- 0.31 degrees C) or during the cap session (-0.30 +/- 0.13 degrees C). In experiment II the influence of wearing headgear on temperature regulation was studied. Hand skin blood flow, hand T(sk), and heat loss from the hand were recorded in addition to the variables monitored in experiment I. Wearing headgear elevated Tty and peripheral vasomotor responses, whereas Tes evolved in the opposite direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of gas exchange and ventilation in transitions from rest or prior exercise

1977 ◽  
Vol 43 (4) ◽  
pp. 704-708 ◽  
Author(s):  
L. B. Diamond ◽  
R. Casaburi ◽  
K. Wasserman ◽  
B. J. Whipp
Keyword(s):  
Normal Subjects ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Prior Exercise ◽  
Exercise Hyperpnea ◽  
The Mean ◽  
Highly Correlated ◽  
Co2 Flow ◽  
Kinetics Of ◽  
High Work

Seven normal subjects each performed three transitions to a subanaerobic threshold work rate on a cycle ergometer: 1) from rest, 2) from a low work rate (both at 60 rpm), and 3) from a low work rate at 40 rpm to the high work rate at 80 rpm. Oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) were computed breath-by-breath and response kinetics extracted. The mean half-times of VO2, VCO2, and VE were 32, 44, and 49 s, respectively, and were not appreciably affected by the prior exercise or by variation of pedal rate. The kinetics of VE was highly correlated with VCO2 (r = 0.94), with VCO2 leading VE, providing further description of the relation of the exercise hyperpnea to CO2 flow to the lungs.

Core temperature "null zone"

1991 ◽  
Vol 71 (4) ◽  
pp. 1289-1295 ◽  
Author(s):  
I. B. Mekjavic ◽  
C. J. Sundberg ◽  
D. Linnarsson
Keyword(s):  
Core Temperature ◽  
Recovery Period ◽  
Rest Period ◽  
Cycle Ergometer ◽  
Work Rate ◽  
The Core ◽  
Maximum Work ◽  
Male Subjects ◽  
Shivering Thermogenesis ◽  
Peak Value

An experimental protocol was designed to investigate whether human core temperature is regulated at a “set point” or whether there is a neutral zone between the core thresholds for shivering thermogenesis and sweating. Nine male subjects exercised on an underwater cycle ergometer at a work rate equivalent to 50% of their maximum work rate. Throughout an initial 2-min rest period, the 20-min exercise protocol, and the 100-min recovery period, subjects remained immersed to the chin in water maintained at 28 degrees C. On completion of the exercise, the rate of forehead sweating (Esw) decayed from a mean peak value of 7.7 +/- 4.2 (SD) to 0.6 +/- 0.3 g.m-2.min-1, which corresponds to the rate of passive transpiration, at core temperatures of 37.42 +/- 0.29 and 37.39 +/- 0.48 degrees C, as measured in the esophagus (Tes) and rectum (Tre), respectively. Oxygen uptake (VO2) decreased rapidly from an exercising level of 2.11 +/- 0.25 to 0.46 +/- 0.09 l/min within 4 min of the recovery period. Thereafter, VO2 remained stable for approximately 20 min, eventually increased with progressive cooling of the core region, and was elevated above the median resting values determined between 15 and 20 min at Tes = 36.84 +/- 0.38 degrees C and Tre = 36.80 +/- 0.39 degrees C. These results indicate that the core temperatures at which sweating ceases and shivering commences are significantly different (P less than 0.001) regardless of whether core temperature is measured within the esophagus or rectum.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscular efficiency during steady-rate exercise: effects of speed and work rate

1975 ◽  
Vol 38 (6) ◽  
pp. 1132-1139 ◽  
Author(s):  
G. A. Gaesser ◽  
G. A. Brooks
Keyword(s):  
Coupling Efficiency ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Base Line ◽  
Exponential Relationship ◽  
Steady Rate ◽  
Resting Metabolism ◽  
Traditional Mode ◽  
Delta G ◽  
Male Subjects

In a comparison of traditional and theoretical exercise efficiency calculations male subjects were studied during steady-rate cycle ergometer exercises of “0,” 200, 400, 600, and 800 kgm/min while pedaling at 40, 60, 80, and 100 rpm. Gross (no base-line correction), net (resting metabolism as base-line correction), work (unloading cycling as base-line correction), and delta (measurable work rate as base-line correction) efficiencies were computed. The result that gross (range 7.5–20.4%) and net (9.8–24.1%) efficiencies increased with increments in work rate was considered to be an artifact of calculation. A LINEAR OR SLIGHTLY EXPONENTIAL RELATIONSHIP BETWEEN CALORIC OUTPUT AND WORK RATE DICTATES EITHER CONSTANT OR DECREASING EFFICIENCY WITH INCREMENTS IN WORK. The delta efficiency (24.4–34.0%) definition produced this result. Due to the difficulty in obtaining 0 work equivalents, the work efficiency definition proved difficult to apply. All definitions yielded the result of decreasing efficiency with increments in speed. Since the theoretical-thermodynamic computation (assuming mitochondrial P/O = 3.0 and delta G = -11.0 kcal/mol for ATP) holds only for CHO, the traditional mode of computation (based upon VO2 and R) was judged to be superior since R less than 1.0. Assuming a constant phosphorylative-coupling efficiency of 60%, the mechanical contraction-coupling efficiency appears to vary between 41 and 57%.

Human temperature regulation during narcosis induced by inhalation of 30% nitrous oxide

1992 ◽  
Vol 73 (6) ◽  
pp. 2246-2254 ◽  
Author(s):  
I. B. Mekjavic ◽  
C. J. Sundberg
Keyword(s):  
Nitrous Oxide ◽  
Temperature Regulation ◽  
Recovery Period ◽  
Cycle Ergometer ◽  
Work Rate ◽  
O2 Uptake ◽  
The Core ◽  
Maximum Work ◽  
Male Subjects ◽  
Shivering Thermogenesis

The study investigated the effect of inhalation of 30% nitrous oxide (N2O) on temperature regulation in humans. Seven male subjects were immersed to the neck in 28 degrees C water on two separate occasions. They exercised at a rate equivalent to 50% of their maximum work rate on an underwater cycle ergometer for 20 min and remained immersed for an additional 100 min after the exercise. In one trial (AIR) the subjects inspired compressed air, and in the other trial (N2O) they inspired a gas mixture containing N2O (20.93% O2–30% N2O-49.07% N2). Sweating, measured at the forehead, and shivering thermogenesis, as reflected by O2 uptake, were monitored throughout the 100-min recovery period. The threshold core temperatures at which sweating was extinguished and shivering was initiated were established relative to resting preexercise levels. Neither the magnitude of the sweating response nor the core threshold at which it was extinguished was significantly affected by the inhalation of N2O. In contrast, shivering thermogenesis was both significantly reduced during the N2O condition and initiated at significantly lower core temperatures [change in esophageal temperature (delta T(es)) = -0.98 +/- 0.33 degrees C and change in rectal temperature (delta T(re)) = -1.26 degrees C] during the N2O than during the AIR condition (delta T(es) = -0.36 +/- 0.31 degrees C and delta T(re) = -0.44 +/- 0.22 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple Sclerosis: Treadmill Versus Cycle Ergometry Maximal Exercise Test Responses

2020 ◽  
Vol 9 (3) ◽  
pp. 113-117
Author(s):  
Garett Griffith ◽  
Badeia Saed ◽  
Tracy Baynard
Keyword(s):  
Multiple Sclerosis ◽  
Aerobic Capacity ◽  
Work Capacity ◽  
Cross Sectional Study ◽  
Cycle Ergometer ◽  
Cycle Ergometry ◽  
Cross Sectional ◽  
Complete Test ◽  
Peak Aerobic Capacity ◽  
Predicted Values

ABSTRACT Background: Multiple sclerosis (MS) is an autoimmune disease that impacts the central nervous system. MS generally results in decreased mobility and work capacity. Our objective was to determine exercise testing responses on both a treadmill and cycle ergometer among individuals with MS who were able to ambulate freely. Methods: Twenty-six individuals with MS participated in a cross-sectional study (44 ± 11 years; body mass index 26.8 ± 6.2 kg·m−2; expanded disability scale score 3.1 ± 0.9), with 24 individuals with complete test data for both treadmill and cycle ergometry tests. Peak aerobic capacity (VO2peak) for both treadmill and cycle ergometry tests were measured with indirect calorimetry. Results: Participants safely completed both treadmill and cycle ergometry tests, and treadmill testing yielded higher values (26.7 ± 6.4 mL·kg−1·min−1) compared with cycle ergometry (23.7 ± 5.7 mL·kg−1·min−1), with values ~12% greater for treadmill. When comparing tests to their respected predicted values within modality, treadmill tests were 8% lower and cycle ergometry tests were 10% lower than predicted. Conclusions: While peak aerobic capacity was very low for this population, treadmill tests were still higher than cycle ergometry data, with this difference between modes being similar to that observed in healthy adult populations. Additional research is required to determine if these findings are impacted by participation in physical activity or regular exercise.

scholarly journals Confinement, partial sleep deprivation and defined physical activity–influence on cardiorespiratory regulation and capacity

2021 ◽  
Author(s):  
Jessica Koschate ◽  
Uwe Drescher ◽  
Uwe Hoffmann
Keyword(s):  
Physical Activity ◽  
Cardiorespiratory Fitness ◽  
Space Mission ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Binary Sequences ◽  
Kinetics Parameters ◽  
Slow Heart Rate ◽  
Partial Sleep Deprivation ◽  
Sleep Schedule

Abstract Introduction Adequate cardiorespiratory fitness is of utmost importance during spaceflight and should be assessable via moderate work rate intensities, e.g., using kinetics parameters. The combination of restricted sleep, and defined physical exercise during a 45-day simulated space mission is expected to slow heart rate (HR) kinetics without changes in oxygen uptake ($${\dot{\text{V}}\text{O}}_{{2}}$$ V ˙ O 2 ) kinetics. Methods Overall, 14 crew members (9 males, 5 females, 37 ± 7 yrs, 23.4 ± 3.5 kg m−2) simulated a 45-d-mission to an asteroid. During the mission, the sleep schedule included 5 nights of 5 h and 2 nights of 8 h sleep. The crew members were tested on a cycle ergometer, using pseudo-random binary sequences, changing between 30 and 80 W on day 8 before (MD-8), day 22 (MD22) and 42 (MD42) after the beginning and day 4 (MD + 4) following the end of the mission. Kinetics information was assessed using the maxima of cross-correlation functions (CCFmax). Higher CCFmax indicates faster responses. Results CCFmax(HR) was significantly (p = 0.008) slower at MD-8 (0.30 ± 0.06) compared with MD22 (0.36 ± 0.06), MD42 (0.38 ± 0.06) and MD + 4 (0.35 ± 0.06). Mean HR values during the different work rate steps were higher at MD-8 and MD + 4 compared to MD22 and MD42 (p < 0.001). Discussion The physical training during the mission accelerated HR kinetics, but had no impact on mean HR values post mission. Thus, HR kinetics seem to be sensitive to changes in cardiorespiratory fitness and may be a valuable parameter to monitor fitness. Kinetics and capacities adapt independently in response to confinement in combination with defined physical activity and sleep.

scholarly journals The Influence of Maturation on the Oxygen Uptake Efficiency Slope

2012 ◽  
Vol 24 (3) ◽  
pp. 347-356 ◽  
Author(s):  
Michael P. Rogowski ◽  
Justin P. Guilkey ◽  
Brooke R. Stephens ◽  
Andrew S. Cole ◽  
Anthony D. Mahon
Keyword(s):  
Oxygen Uptake ◽  
Body Mass ◽  
Cycle Ergometer ◽  
Group Differences ◽  
Healthy Male ◽  
Uptake Efficiency ◽  
Graded Exercise ◽  
Oxygen Uptake Efficiency Slope ◽  
Male Subjects ◽  
One Way Anova

This study examined the influence of maturation on the oxygen uptake efficiency slope (OUES) in healthy male subjects. Seventy-six healthy male subjects (8–27 yr) were divided into groups based on maturation status: prepubertal (PP), midpubertal (MP), late-pubertal (LP), and young-adult (YA) males. Puberty status was determined by physical examination. Subjects performed a graded exercise test on a cycle ergometer to determine OUES. Group differences were assessed using a one-way ANOVA. OUES values (VO2L·min1/log10VEL·min−1) were lower in PP and MP compared with LP and YA (p < .05). When OUES was expressed relative to body mass (VO2mL·kg−1·min−1/log10VEmL·kg−1·min−1) differences between groups reversed whereby PP and MP had higher mass relative OUES values compared with LP and YA (p < .05). Adjusting OUES by measures of body mass failed to eliminate differences across maturational groups. This suggests that qualitative factors, perhaps related to oxidative metabolism, account for the responses observed in this study.

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