Stability of Heart Rate at Physiological Thresholds Between Temperate and Heat Stress Environments in Endurance-Trained Males

2020 ◽  
pp. 1-4
Author(s):  
Ed Maunder ◽  
Daniel J. Plews ◽  
Fabrice Merien ◽  
Andrew E. Kilding
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Relative Humidity ◽  
Blood Lactate ◽  
Endurance Athletes ◽  
Heart Rates ◽  
Stress Environments ◽  
Positive Correlations ◽  
Hot Environments ◽  
Stress Training

Many endurance athletes perform specific blocks of training in hot environments in “heat stress training camps.” It is not known if physiological threshold heart rates measured in temperate conditions are reflective of those under moderate environmental heat stress. A total of 16 endurance-trained cyclists and triathletes performed incremental exercise assessments in 18°C and 35°C (both 60% relative humidity) to determine heart rates at absolute blood lactate and ventilatory thresholds. Heart rate at fixed blood lactate concentrations of 2, 3, and 4 mmol·L−1 and ventilatory thresholds were not significantly different between environments (P > .05), despite significant heat stress-induced reductions in power output of approximately 10% to 17% (P < .05, effect size = 0.65–1.15). The coefficient of variation for heart rate at these blood lactate concentrations (1.4%−2.9%) and ventilatory thresholds (2.3%−2.7%) between conditions was low, with significant strong positive correlations between measurements in the 2 environments (r = .92–.95, P < .05). These data indicate heart rates measured at physiological thresholds in temperate environments are reflective of measurements taken under moderate environmental heat stress. Therefore, endurance athletes embarking on heat stress training camps can use heart rate–based thresholds ascertained in temperate environments to prescribe training under moderate environmental heat stress.

Heat Stress Training Camps for Endurance Sport: A Descriptive Case Study of Successful Monitoring in 2 Ironman Triathletes

2020 ◽  
Vol 15 (1) ◽  
pp. 146-150
Author(s):  
Ed Maunder ◽  
Andrew E. Kilding ◽  
Christopher J. Stevens ◽  
Daniel J. Plews
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Heat Stress ◽  
Well Being ◽  
Self Report ◽  
Endurance Athletes ◽  
Resting Heart Rate ◽  
Resting Heart Rate Variability ◽  
Stress Training

A common practice among endurance athletes is to purposefully train in hot environments during a “heat stress camp.” However, combined exercise-heat stress poses threats to athlete well-being, and therefore, heat stress training has the potential to induce maladaptation. This case study describes the monitoring strategies used in a successful 3-week heat stress camp undertaken by 2 elite Ironman triathletes, namely resting heart rate variability, self-report well-being, and careful prescription of training based on previously collected physiological data. Despite the added heat stress, training volume very likely increased in both athletes, and training load very likely increased in one of the athletes, while resting heart rate variability and self-report well-being were maintained. There was also some evidence of favorable metabolic changes during routine laboratory testing following the camp. The authors therefore recommend that practitioners working with endurance athletes embarking on a heat stress training camp consider using the simple strategies employed in the present case study to reduce the risk of maladaptation and nonfunctional overreaching.

P4423Extreme bradycardia in athletes is due to intrinsic changes within the heart

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
M D Flannery ◽  
F Sully ◽  
K Janssens ◽  
G Morris ◽  
J Kalman ◽  
...  
Keyword(s):  
Heart Rate ◽  
Vagal Tone ◽  
Endurance Athletes ◽  
Valsalva Manoeuvre ◽  
Resting Heart Rate ◽  
Maximum Heart Rate ◽  
Vo2 Max ◽  
Heart Rates ◽  
Intrinsic Heart Rate ◽  
Autonomic Blockade

Abstract Background It is well known that athletes and in particular endurance athletes have lower resting heart rates than non-athletes. This has generally been considered a healthy adaptation. Traditionally this was thought be due to increased vagal tone. Several studies have shown that endurance athletes continue to have lower heart rates in the absence of autonomic influence suggesting bradycardia is due to intrinsic changes within the heart. A subset of endurance athletes have very low heart rates with Tour de France cyclists having described heart rates in the 30s. It is unclear whether in these elite athletes with very low heart rates the profound bradycardia is due to autonomic influence or intrinsic changes within the heart. Aim The aim of this study was to determine if extreme bradycardia in athletes is due to excess vagal tone or more profound intrinsic changes within the heart. Methods We recruited three cohorts for this study: non-athlete controls (NA), endurance athletes with a documented resting heart rate >40 (EA) and endurance athletes with a resting heart rate <40 (BA). All participants underwent baseline testing including ECG, echocardiography and VO2 max testing. All participants came back on a second occasion for treatment with dual autonomic blockade (DAB) to determine intrinsic heart rate in the following manner. After resting supine for five minutes resting heart rate was measured. Participants were then administered 0.04mg/kg of intravenous atropine. After five minutes participants were then administered 0.05mg/kg of intravenous metoprolol. This was repeated every five minutes until there was no further drop in heart rate or 0.2mg/kg had been administered. The resting heart rate at this stage was recorded as the intrinsic heart rate. Parasympathetic blockade was confirmed by lack of response to Valsalva manoeuvre and sympathetic blockade was confirmed by lack of response to metoprolol. VO2 max testing was then performed to determine maximum heart rate. Results 9 NA (7 male), 10 EA (8 male) and 5 BA (4 male) participated in this study. The average age was similar in all groups (NA 32.9y, EA 32.4y, BA 31.4y). The average resting heart rate was 71.7 in the NA group, 48.3 in the EA group and 41.6 in the BA group (p<0.05 for comparisons between all three groups). Following dual autonomic blockade resting heart rate was 86.0 in the NA group, 76.9 in the EA group and 64.4 in the BA group (p<0.05 for comparisons between all three groups). Maximum heart rate under DAB was 140.1 in the NA group, 138.0 in the EA group and 140.4 in the BA group. These differences were not significant. Conclusion In athletes with very low heart rates, bradycardia is due to more profound intrinsic changes within the heart. Acknowledgement/Funding NHMRC Project Grant

scholarly journals Do Elite Endurance Athletes Report Their Training Accurately?

2014 ◽  
Vol 9 (1) ◽  
pp. 85-92 ◽  
Author(s):  
Øystein Sylta ◽  
Espen Tønnessen ◽  
Stephen Seiler
Keyword(s):  
Heart Rate ◽  
Blood Lactate ◽  
Intensity Distribution ◽  
Gold Standard ◽  
Reporting Guidelines ◽  
Training Data ◽  
Endurance Athletes ◽  
Altitude Training ◽  
Expert Analysis ◽  
Cross Country

Purpose:The purpose of this study was to validate the accuracy of self-reported (SR) training duration and intensity distribution in elite endurance athletes.Methods:Twenty-four elite cross-country skiers (25 ± 4 y, 67.9 ± 9.88 kg, 75.9 ± 6.50 mL · min−1 · kg−1) SR all training sessions during an ~14-d altitude-training camp. Heart rate (HR) and some blood lactate measurements were collected during 466 training sessions. SR training was compared with recorded training duration from HR monitors, and SR intensity distribution was compared with expert analysis (EA) of all session data.Results:SR training was nearly perfectly correlated with recorded training duration (r = .99), but SR training was 1.7% lower than recorded training duration (P < .001). SR training duration was also nearly perfectly correlated (r = .95) with recorded training duration >55% HRmax, but SR training was 11.4% higher than recorded training duration >55% HRmax (P < .001) due to SR inclusion of time <55% HRmax. No significant differences were observed in intensity distribution in zones 1–2 between SR and EA comparisons, but small discrepancies were found in zones 3–4 (P < .001).Conclusions:This study provides evidence that elite endurance athletes report their training data accurately, although some small differences were observed due to lack of a SR “gold standard.” Daily SR training is a valid method of quantifying training duration and intensity distribution in elite endurance athletes. However, additional common reporting guidelines would further enhance accuracy.

Hepatic clearance of indocyanine green in man under thermal and exercise stresses

1965 ◽  
Vol 20 (3) ◽  
pp. 384-394 ◽  
Author(s):  
Loring B. Rowell ◽  
John R. Blackmon ◽  
Richard H. Martin ◽  
John A. Mazzarella ◽  
Robert A. Bruce
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Indocyanine Green ◽  
Blood Lactate ◽  
Hepatic Blood Flow ◽  
Rectal Temperature ◽  
Hepatic Clearance ◽  
Work Capacity ◽  
Heart Rates ◽  
Icg Clearance

At 78 and 110 F hepatic clearance of indocyanine green (ICG), O2 intake, heart rate, blood lactate, and rectal temperature were measure on nine men unacclimatized to heat during treadmill exercise, requiring 45–95% of maximal O2 intake (max Vo2). Percentage of resting ICG clearance was inversely proportional to percentage of maximal O2 intake at 78 F (ggr = -0.78) and 110 F (ggr = -0.81). Clearance of ICG was 20% less at 110 F than at 78 F at all metabolic rates above 26% of maximal Vo2. Measurements of hepatic blood flow in three men at 110 F validate these estimates of percentage decrements in hepatic blood flow. Submaximal and maximal Vo2 and maximal heart rates were unaltered by heat, but maximal heart rates were reached during submaximal work at 110 F. Decreased work capacity at 110 F was unrelated to rectal temperature or blood lactate; the latter was unaffected by temperature. The liver and the kidneys may divert to the skin sufficient blood to obviate the need for additional increments in cardiac output during work at high temperature. Maximal decrements in hepatic blood flow at lower work intensities may contribute to diminished work capacity at 110 F. hepatic blood flow during exercise; lactic acid and heat stress; rectal temperature; heart rate and temperature; maximal o2 intake, influence of temperature; temperature redistribution of blood flow; work capacity, effect of heat Submitted on October 30, 1964

Exercise and Heat Stress: Inflammation and the Iron Regulatory Response

2021 ◽  
pp. 1-6
Author(s):  
Alannah K.A. McKay ◽  
Rachel McCormick ◽  
Nicolin Tee ◽  
Peter Peeling
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Venous Blood ◽  
Treadmill Running ◽  
Maximum Heart Rate ◽  
Physiological Strain ◽  
Running Speed ◽  
Hot Environments ◽  
The Impact ◽  
Cool Conditions

This study determined the impact of heat stress on postexercise inflammation and hepcidin levels. Twelve moderately trained males completed three, 60-min treadmill running sessions under different conditions: (a) COOL, 18 °C with speed maintained at 80% maximum heart rate; (b) HOTHR, 35 °C with speed maintained at 80% maximum heart rate; and (c) HOTPACE, 35 °C completed at the average running speed from the COOL trial. Venous blood samples were collected pre-, post-, and 3-hr postexercise and analyzed for serum ferritin, interleukin-6 (IL-6), and hepcidin concentrations. Average HR was highest during HOTPACE compared with HOTHR and COOL (p < .001). Running speed was slowest in HOTHR compared with COOL and HOTPACE (p < .001). The postexercise increase in IL-6 was greatest during HOTPACE (295%; p = .003). No differences in the IL-6 response immediately postexercise between COOL (115%) and HOTHR (116%) were evident (p = .992). No differences in hepcidin concentrations between the three trials were evident at 3 hr postexercise (p = .407). Findings from this study suggest the IL-6 response to exercise is greatest in hot compared with cool conditions when the absolute running speed was matched. No differences in IL-6 between hot and cool conditions were evident when HR was matched, suggesting the increased physiological strain induced from training at higher intensities in hot environments, rather than the heat per se, is likely responsible for this elevated response. Environmental temperature had no impact on hepcidin levels, indicating that exercising in hot conditions is unlikely to further impact transient alterations in iron regulation, beyond that expected in temperate conditions.

EFFECTS OF INONIZING RADIATION CAUSED HEAT STRESS ON THE HUMAN BODY FOR STANDARD ISO 7243

2013 ◽  
pp. 47-57
Author(s):  
Van Trong Le ◽  
Thi Tuyet Mai Nguyen ◽  
Thi Xuan Duyen Nguyen ◽  
Ba Luan Nguyen ◽  
Tuyen Pham ◽  
...  
Keyword(s):  
Heat Stress ◽  
Risk Assessments ◽  
Management Systems ◽  
Temperature Index ◽  
Wet Bulb Globe Temperature ◽  
Simple Index ◽  
Simple Tool ◽  
Results Management ◽  
Globe Temperature ◽  
Hot Environments

Objectives: Presents heat stress Standard ISO 7243, which is based upon the wet bulb globe temperature index (WBGT), and considers its suitability for use worldwide. Materials and Methods: The WBGT index are considered and how it is used in ISO 7243 and across the world as a simple index for monitoring and assessing hot environments. Results: Management systems, involving risk assessments, that take account of context and culture, are required to ensure successful use of the standard and global applicability. For use outdoors, a WBGT equation that includes solar absorptivity is recommended. A ‘clothed WBGT’ is proposed to account for the effects of clothing. Conclusion: ISO 7243 is a simple tool to assess the heat stress and may be applicated worldwide.

scholarly journals The Effect Of Outside Corridor’s Orientation to Interior Thermal Condition at Lawang Sewu Semarang.

2018 ◽  
Vol 73 ◽  
pp. 01011
Author(s):  
Benediktus Yosef Arya Wastunimpuna ◽  
Wahyu Setia Budi ◽  
Erni Setyowati
Keyword(s):  
Heat Stress ◽  
Relative Humidity ◽  
Thermal Condition ◽  
Natural Ventilation ◽  
Thermal Conditions ◽  
Standard Theory ◽  
Hot Wire ◽  
Air Movement ◽  
Dutch Colonial

The outside corridor of Dutch Colonial Building in Indonesia was made to make the temperature of the room more comfortable. Lawang Sewu Building in Semarang is one example of a building that has an outside corridor along the building and until now still use natural ventilation. This study focuses on finding out whether there is a difference on the thermal conditions of each room’s orientation, so after that we know the effect of orientation of the outdoor corridor to the temperature of the interior. In this study the experiment based on measurement using Heat Stress WBGT Meter for Wet Bulb Temperature, Dry Bulb Temperature, Relative Humidity, and KW0600653 Hot Wire Anemometer for the air movement. The data will be analysed using thermal standard theory to find out which point has the most comfortable thermal conditions.. At the end of this study will be found the effect of corridor’s orientation to thermal condition of the interior in Lawang Sewu Semarang.

scholarly journals The tepary bean genome provides insight into evolution and domestication under heat stress

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Samira Mafi Moghaddam ◽  
Atena Oladzad ◽  
Chushin Koh ◽  
Larissa Ramsay ◽  
John P. Hart ◽  
...  
Keyword(s):  
Heat Stress ◽  
Common Bean ◽  
Sonoran Desert ◽  
Climate Adaptation ◽  
Human Consumption ◽  
Disease Resistance Gene ◽  
Gene Repertoire ◽  
Tepary Bean ◽  
Hot Environments ◽  
Insight Into

AbstractTepary bean (Phaseolus acutifolis A. Gray), native to the Sonoran Desert, is highly adapted to heat and drought. It is a sister species of common bean (Phaseolus vulgaris L.), the most important legume protein source for direct human consumption, and whose production is threatened by climate change. Here, we report on the tepary genome including exploration of possible mechanisms for resilience to moderate heat stress and a reduced disease resistance gene repertoire, consistent with adaptation to arid and hot environments. Extensive collinearity and shared gene content among these Phaseolus species will facilitate engineering climate adaptation in common bean, a key food security crop, and accelerate tepary bean improvement.

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