Ice ingestion with a long rest interval increases the endurance exercise capacity and reduces the core temperature in the heat

This study examined the effects of variations in air velocity on time to exhaustion and thermoregulatory and perceptual responses to exercise in a hot environment. Eight male volunteers completed stationary cycle exercise trials at 70% peak oxygen uptake until exhaustion in an environmental chamber maintained at 30 °C and 50% relative humidity. Four air velocity conditions, 30, 20, 10, and 0 km/h, were tested, and the headwind was directed at the frontal aspect of the subject by 2 industrial fans, with blade diameters of 1 m and 0.5 m, set in series and positioned 3 m from the subject’s chest. Mean ± SD time to exhaustion was 90 ± 17, 73 ± 16, 58 ± 13, and 41 ± 10 min in 30-, 20-, 10-, and 0-km/h trials, respectively, and was different between all trials (P < 0.05). There were progressive elevations in the rate of core temperature rise, mean skin temperature, and perceived thermal sensation as airflow decreases (P < 0.05). Core temperature, heart rate, cutaneous vascular conductance, and perceived exertion were higher and evaporative heat loss was lower without airflow than at any given airflow (P < 0.05). Dry heat loss and plasma volume were similar between trials (P > 0.05). The present study demonstrated a progressive reduction in time to exhaustion as air velocity decreases. This response is associated with a faster rate of core temperature rise and a higher skin temperature and perceived thermal stress with decreasing airflow. Moreover, airflow greater than 10 km/h (2.8 m/s) might contribute to enhancing endurance exercise capacity and reducing thermoregulatory, cardiovascular, and perceptual strain during exercise in a hot environment.

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Rising vs. falling phases of core temperature on endurance exercise capacity in the heat

European Journal of Applied Physiology ◽

10.1007/s00421-019-04292-6 ◽

2020 ◽

Vol 120 (2) ◽

pp. 481-491 ◽

Cited By ~ 1

Author(s):

Hidenori Otani ◽

Mitsuharu Kaya ◽

Heita Goto ◽

Akira Tamaki

Keyword(s):

Exercise Capacity ◽

Core Temperature ◽

Endurance Exercise

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Olive leaf extract prevents obesity, cognitive decline, and depression and improves exercise capacity in mice

Scientific Reports ◽

10.1038/s41598-021-90589-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Toshio Mikami ◽

Jimmy Kim ◽

Jonghyuk Park ◽

Hyowon Lee ◽

Pongson Yaicharoen ◽

...

Keyword(s):

Cognitive Decline ◽

Exercise Capacity ◽

Endurance Exercise ◽

Leaf Extract ◽

Metabolic Diseases ◽

Olive Leaf ◽

Olive Leaf Extract ◽

Hypoxic Conditions ◽

G Protein Coupled ◽

Antioxidant Effects

AbstractObesity is a risk factor for development of metabolic diseases and cognitive decline; therefore, obesity prevention is of paramount importance. Neuronal mitochondrial dysfunction induced by oxidative stress is an important mechanism underlying cognitive decline. Olive leaf extract contains large amounts of oleanolic acid, a transmembrane G protein-coupled receptor 5 (TGR5) agonist, and oleuropein, an antioxidant. Activation of TGR5 results in enhanced mitochondrial biogenesis, which suggests that olive leaf extract may help prevent cognitive decline through its mitochondrial and antioxidant effects. Therefore, we investigated olive leaf extract’s effects on obesity, cognitive decline, depression, and endurance exercise capacity in a mouse model. In physically inactive mice fed a high-fat diet, olive leaf extract administration suppressed increases in fat mass and body weight and prevented cognitive declines, specifically decreased working memory and depressive behaviors. Additionally, olive leaf extract increased endurance exercise capacity under atmospheric and hypoxic conditions. Our study suggests that these promising effects may be related to oleanolic acid’s improvement of mitochondrial function and oleuropein’s increase of antioxidant capacity.

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Temperature Monitoring and Perioperative Thermoregulation

Anesthesiology ◽

10.1097/aln.0b013e31817f6d76 ◽

2008 ◽

Vol 109 (2) ◽

pp. 318-338 ◽

Cited By ~ 341

Author(s):

Daniel I. Sessler ◽

David S. Warner ◽

Mark A. Warner

Keyword(s):

Body Temperature ◽

General Anesthesia ◽

Core Temperature ◽

Core Body Temperature ◽

Neuraxial Anesthesia ◽

General Anesthetics ◽

The Core ◽

Core Body ◽

Dose Dependent ◽

Body Heat

Most clinically available thermometers accurately report the temperature of whatever tissue is being measured. The difficulty is that no reliably core-temperature-measuring sites are completely noninvasive and easy to use-especially in patients not undergoing general anesthesia. Nonetheless, temperature can be reliably measured in most patients. Body temperature should be measured in patients undergoing general anesthesia exceeding 30 min in duration and in patients undergoing major operations during neuraxial anesthesia. Core body temperature is normally tightly regulated. All general anesthetics produce a profound dose-dependent reduction in the core temperature, triggering cold defenses, including arteriovenous shunt vasoconstriction and shivering. Anesthetic-induced impairment of normal thermoregulatory control, with the resulting core-to-peripheral redistribution of body heat, is the primary cause of hypothermia in most patients. Neuraxial anesthesia also impairs thermoregulatory control, although to a lesser extent than does general anesthesia. Prolonged epidural analgesia is associated with hyperthermia whose cause remains unknown.

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Abstract 10475: Heat Loss Augmented by Extracorporeal Circulation is Associated with Overcooling in Cardiac Arrest Survivors Who Underwent Targeted Temperature Management

Circulation ◽

10.1161/circ.144.suppl_2.10475 ◽

2021 ◽

Vol 144 (Suppl_2) ◽

Author(s):

Byungkook Lee ◽

Dong Hun Lee

Keyword(s):

Water Temperature ◽

Core Temperature ◽

Neurological Outcome ◽

Temperature Management ◽

Extracorporeal Circuit ◽

Matched Cohort ◽

Maintenance Period ◽

Neurological Outcomes ◽

The Core ◽

Poor Neurological Outcome

Introduction: Extracorporeal circuit-based salvage therapy can affect targeted temperature management (TTM) in comatose out-of-hospital cardiac arrest (OHCA) survivors. We investigated the association of patients with extracorporeal device with TTM and neurological outcome. Methods: We performed a retrospective analysis using prospectively collected data from adult comatose OHCA survivors who underwent TTM between October 2015 and December 2020. We defined patients with ECMO and/or CRRT as the extracorporeal group. We calculated the cooling rate during the induction period; the minimum, maximum, and mean time-weighted core temperatures (TWCT), and the standard deviation (SD) of the core temperature and water temperature during the maintenance period based on the temperature measured every minute. We defined the sum of TWCT more and less than 33°C as positive and negative TWCT, respectively. The primary outcome was a poor neurological outcome, defined as cerebral performance category 3-5. We used propensity score (PS) matching to adjust the characteristics of patients who required an extracorporeal circuit device. Results: Of the 223 included patients, 140 (62.8%) patients had poor neurological outcome and 40 (17.9%) patients were categorized into the extracorporeal group. The extracorporeal group had a rapid cooling rate (2.08°C/h [1.13-3.73] vs. 1.24°C/h [0.77-1.79]; p < 0.001). The extracorporeal group had lower mean core temperature; higher core temperature SD; lower positive TWCT; higher negative TWCT; and higher maximum, minimum, and mean water temperature than the no-extracorporeal group. In PS matched cohort, the extracorporeal group had a lower minimum core temperature, lower mean core temperature, higher core temperature SD, higher negative TWCT, higher maximum water temperature, and higher mean water temperature. The neurological outcomes were not different between the two groups, in either the whole or PS-matched cohort. Conclusions: The extracorporeal group achieved the target temperature earlier. The core temperature distribution during the maintenance period was further skewed below 33°C in the extracorporeal group. The extracorporeal group had similar neurological outcomes to the no-extracorporeal group.

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Simulating the action of zeitgebers on a coupled two-oscillator model of the human circadian system

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1984.247.3.r418 ◽

1984 ◽

Vol 247 (3) ◽

pp. R418-R426

Author(s):

P. H. Gander ◽

R. E. Kronauer ◽

C. A. Czeisler ◽

M. C. Moore-Ede

Keyword(s):

Core Temperature ◽

Activity Rhythm ◽

Human Subjects ◽

Model Performance ◽

The Other ◽

Oscillator Model ◽

Temporal Isolation ◽

The Core ◽

Temperature Rhythm ◽

Rest Activity

Our two-oscillator model was originally designed to describe the circadian rhythms of human subjects maintained in temporal isolation. The performance of this model in response to simulated environmental synchronizing cycles (zeitgebers) is examined here. Six distinct types of synchronization are demonstrated between the x oscillator (postulated to regulate the core temperature rhythm), the y oscillator (postulated to regulate the rest-activity rhythm), and z (the zeitgeber). Four types of synchronization are identifiable, if we consider only the periods of the three oscillators. Both x and y may be synchronized by z; either may synchronize with z while the other exhibits a different period; or x, y, and z may each show different periods. Two further classes of synchronization are discernible when phase criteria are taken into account. When either x or y is on the verge of desynchronizing from the other two oscillators, it undergoes periodic phase modulations while retaining the common overall period. The type of synchronization observed depends on the periods of x, y, and z and on the strength of the z drive. The effects of modifying each of these parameters have been systematically investigated by simulation, and model performance is summarized in terms of range of entrainment "maps." These constitute extensive sets of predictions about expected patterns of entrainment of the core temperature and rest-activity rhythms of human subjects exposed to various environmental zeitgebers. Experimental data are available against which model predictions can be tested.

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