Reductions in cardiac output, central blood volume, and stroke volume with thermal stress in normal men during exercise.

Rowell, L. B.; Marx, Hellmut; Bruce, R A; Conn, Robert D.; Kusumi, Fusako

doi:10.1172/jci105484

Cited by 223 publications

(179 citation statements)

References 24 publications

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“…During physical exercise in the heat, the reduction of stro ke volume has been shown to be an important mechani sm limiting physical performance (29). In a hot environment at heavy work loads the lowered stroke volume seems to prevent any thermally induced rise in cardiac output (5,18,29,32), and increments in skin blood flow occur through redistribution of the blood flow from visceral organ s (27) and inactive muscles (14).…”

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confidence: 99%

“…In a hot environment at heavy work loads the lowered stroke volume seems to prevent any thermally induced rise in cardiac output (5,18,29,32), and increments in skin blood flow occur through redistribution of the blood flow from visceral organ s (27) and inactive muscles (14). Therefore, una cclimated subject s cannot reach a circulatory and ther mal steady sta te durin g heavy work in the heat, and the work period s tend to be short.…”

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confidence: 99%

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Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Smolander¹,

Ilmarinen²,

Korhonen³

et al. 1987

Scand J Work Environ Health

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(1987) 37 -46. Eight ph ysicalIy tra ined and eight untrained , una cclimated men walked on a treadmill at 30 010 of their maximum oxygen consumption up to 3.5 h in a the rmoneutral [20°C / 40 010 relative humid ity {RH) J, a warm hum id (30°C /8 0 % RH), and a hot dry (40°C I2 0 010 RH ) environment while wearing indu str ial work clothing. Their oxygen consumption, rectal and skin temperat ures, sweat ing, card iac output, hea rt rate, stroke volume, and peripheral blood pressure were measured du ring the tests . Thirteen of the 32 heat stress tests were prematurely stopped du e to high rectal temperature, high heart rate, subjective fa tigue, or heat syncope . The physiological str ain, as indicated by the rectal tempe ratur e and heart rate, was not significantl y different between th e warm humid and hot dr y environmen ts (wet bulb globe temperature -28°C). Th e rectal temp eratur e and heart rat e responses of the physicalIy train ed and untrained subjects did not diff er in any of the environments . In th e heat, the heart ra te was significa ntly higher than in the thermoneut ral environm ent , but becau se of the markedly redu ced stroke volume the average ca rdiac output was not differen t between the three environ ments. The impaired work perform an ce in the hea t seemed mainly to be related to the circulat ory instability accompanying the increased cuta neous circulation .Key terms: bod y temp erature, central circulation, heat stress indices, hot dry environment, peripheral circulati on , physical fitn ess, prol onged exercise, sweating, warm humid environment, work perform an ce.

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confidence: 99%

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confidence: 99%

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Smolander¹,

Ilmarinen²,

Korhonen³

et al. 1987

Scand J Work Environ Health

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“…However, while HR increases under these conditions, stroke volume is reduced, likely because of reduced ventricular filling time associated with tachycardia as well as peripheral displacement of blood volume (Rowell, 1974;González-Alonso et al, 2000, 2004Gonzalez-Alonso, 2003;Trinity et al, 2010). This may result in a 2-3 L·min -1 reduction in cardiac output (Rowell et al, 1966;González-Alonso et al, 1999;Périard et al, 2011), and this reduction becomes markedly more pronounced if hyperthermia is accompanied with dehydration , 1997). Lower cardiac output during high-intensity exercise in the heat leads to decreased leg blood flow, mean arterial pressure (MAP), and oxygen delivery, which ultimately impairs muscle aerobic capacity (Gonzalez-Alonso, 2003).…”

Section: Cardiovascular-related Factorsmentioning

confidence: 99%

Precooling and Warm-up Effects on Time Trial Cycling Performance During Heat Stress

Al-Horani

Wingo

2015

Medicine &Amp; Science in Sports &Amp; Exercise

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The aim of this study was to investigate the separate and combined effects of precooling and warm-up on a subsequent cycling time trial in a hot environment. Nine healthy men (mean±SD age=24±5 years; body mass=74.7±4.5 kg; height=171.4±7.7 cm; body fat=12.9±5.2%) completed 3 simulated 16.1-km time trials on a cycle ergometer in a hot environment (~33 °C, 45% relative humidity) after: 1) 20 min of fluid ingestion (10 °C ) followed by 30 min of ice-slurry ingestion (-1 °C ) coupled with ice-vest (PREC), 2) 30 min of ice-slurry ingestion coupled with ice-vest followed by 20 min of warm-up including ice-slurry and ice-vest (COMBO), 3) 30 min of fluid ingestion (10 °C) followed by 20 min of warm-up (WU). At baseline, rectal temperature (T re ), mean skin temperature ( sk ), and mean body temperature ( b ) were similar among treatments (all P>0.05). After treatment administration and before the start of the time trial, T re was lower in PREC (36.1±0.3) and COMBO (36.9±0.4) compared to WU (37.6±0.2) (all P<0.05). sk and b were all lower in PREC than COMBO and WU, and were lower in COMBO than WU (all P<0.05). T re remained lower in PREC than WU throughout exercise and was lower in PREC than COMBO for the first 12 km (all P<0.01), while T re in COMBO remained lower than WU for the first 4 km. sk during PREC was lower than COMBO at 4 and 8 km and lower than WU at 0 and 4 km, while during COMBO it was lower than WU at 0 and 4 km (all P<0.05). Heart rate (HR) at baseline was lower in PREC than COMBO and WU (68±10, 106±12, 101±13 beats/min, respectively; P<0.001). During exercise, HR increased similarly among all treatments throughout exercise (all P>0.05). Local sweat rate (SR) was lower in PREC than COMBO and WU for the first 4 km (P < iv ACKNOWLEDGMENTS All praise is due to Allah, the entirely merciful; I thank him and praise him. He is the one who protects and guards me in the days when I work, and in the nights when I sleep. He amply bestowed his favors and bounties upon me, and gave me from all I asked of him, and if I should count his favors, surely I could not enumerate.Then, I would like to express my deepest gratitude to my advisor Dr. Jonathan Wingo for his guidance, knowledge, patience, diligence, and dedication throughout this dissertation stages.He was very generous in teaching the procedures of research, from how to professionally use the laboratory equipment, to how to write a solid work of research. He has been sincere, respectful, and hardworking. I am also thankful to my dissertation committee, Dr. Philip Bishop, Dr. Mark Richardson, Dr. Edward Mansfield, and Dr. John Vincent. Their inputs, suggestions, and recommendations were very effective in directing the research into the right way. Also I thank them for their cooperation and sacrifices to finish this dissertation successfully.

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“…Fatigue was traditionally related to the metabolic occurrence of ending point during the exercise in which glycogen concentration within the muscle was depleted completely (Bergström, Hermansen, Hultman, & Saltin, 1967). Furthermore, cardiovascular (González-Alonso & Calbet, 2003;Rowell, Marx, Bruce, Conn, & Kusumi, 1966) and metabolic load, and temperature adjustment are likely peripheral candidates for the fatigue outbreak during long exercises (Hargreaves & Febbraio, 1998).…”

Section: Tablementioning

confidence: 99%

Role of Central Fatigue in Resistance and Endurance Exercises: An Emphasis on Mechanisms and Potential Sites

Sadri¹,

Khani²,

Sadri³

2014

sgia

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SUMMARYAn exercise-induced reduction in maximal force production, or the inability to continue an activity with enough force, is defined as fatigue. Although the etiology of fatigue is complex, it can be divided into two distinct components: central and peripheral. Central fatigue is the progressive exerciseinduced loss of the voluntary activation, or decrease in the neural stimulation, of the muscle, thereby reducing maximal force production. Considering the different mechanisms of strength and endurance activities as well as previous research, the authors suggest that there is peripheral fatigue in both kinds of activities. However, the mechanisms of fatigue and the rate of perceived exertion are distinct (mentally, endurance exercise is more difficult). An analysis of fatigue kinetics shows that peripheral fatigue occurs initially, and the central nervous system tries to prevent the disorder via output force through the perceptions of the metabolic condition of the muscle and the activation of additional motor units. Once peripheral fatigue surpasses a certain amount, the central nervous system reduces the number of activated motor units to prevent serious disorders in homeostasis and muscle damage, and protects the central governor. Still, in important and critical situations such as the final stages of running a marathon (when the last flight of runners is observed) and fight-or-flight situations in which someone faces a worse outcome if a task is abandoned, humans can choose one of worse or the worst alternatives to write their final destiny.

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Reductions in cardiac output, central blood volume, and stroke volume with thermal stress in normal men during exercise.

Cited by 223 publications

References 24 publications

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Precooling and Warm-up Effects on Time Trial Cycling Performance During Heat Stress

Role of Central Fatigue in Resistance and Endurance Exercises: An Emphasis on Mechanisms and Potential Sites

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