Exercise stroke volume relative to plasma-volume expansion

Hopper, Mari K.; Coggan, Andrew R.; Coyle, Edward F.

doi:10.1152/jappl.1988.64.1.404

Cited by 101 publications

(63 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus when fluid is not provided, cardiovascular stability is compromised such that exhaustion occurs at an earlier T re during weight-bearing activity. This observation is similar to the response observed between trained and untrained individuals 25) , where the untrained individuals experienced a greater cardiovascular strain at a given T re due to lower blood and stroke volumes 59) . In fact, fluid replacement during work in the heat has been deemed as important as hydration status prior to work 40) .…”

Section: Fluid Replacementsupporting

confidence: 83%

The Management of Heat Stress for the Firefighter: A Review of Work Conducted on Behalf of the Toronto Fire Service

McLellan

Selkirk

2006

Ind Health

View full text Add to dashboard Cite

This report provides a summary of research conducted through a grant provided by the Workplace Safety Insurance Board of Ontario. The research was divided into two phases; first, to define safe work limits for firefighters wearing their protective clothing and working in warm environments; and, the second, to examine strategies to reduce the thermal burden and extend the operational effectiveness of the firefighter. For the first phase, subjects wore their protective ensemble and carried their self-contained breathing apparatus (SCBA) and performed very light, light, moderate or heavy work at 25°C, 30°C or 35°C. Thermal and evaporative resistance coefficients were obtained from thermal manikin testing that allowed the human physiological responses to be compared with modeled data. Predicted continuous work times were then generated using a heat strain model that established limits for increases in body temperature to 38.0°C, 38.5°C and 39.0°C. Three experiments were conducted for the second phase of the project. The first study revealed that replacing the duty uniform pants that are worn under the bunker pants with shorts reduced the thermal strain for activities that lasted longer than 60 min. The second study examined the importance of fluid replacement. The data revealed that fluid replacement equivalent to at least 65% of the sweat lost increased exposure time by 15% compared with no fluid replacement. The last experiment compared active and passive cooling. Both the use of a mister or forearm and hand submersion in cool water significantly increased exposure time compared with passive cooling that involved only removing most of the protective clothing. Forearm and hand submersion proved to be most effective and produced dramatic increases in exposure time that approximated 65% compared with the passive cooling procedure. When the condition of no fluid replacement and passive cooling was compared with fluid replacement and forearm and hand submersion, exposure times were effectively doubled with the latter condition. The heat stress wheel that was generated can be used by Commanders to determine safe work limits for their firefighters during activities that involve wearing their protective clothing and carrying their SCBA.

show abstract

Section: Fluid Replacementsupporting

confidence: 83%

The Management of Heat Stress for the Firefighter: A Review of Work Conducted on Behalf of the Toronto Fire Service

McLellan

Selkirk

2006

Ind Health

View full text Add to dashboard Cite

show abstract

“…It is established that the control of S V during exercise possibly reflects extramyocardial factors of increased blood volume (Hopper et al 1988). It has previously been reported by Gonzalez-Alonso and colleagues ( .…”

Section: Adaptation To Repeated Heat Stressmentioning

confidence: 83%

“…Dehydration during prolonged exercise in the heat increases the response of the fluid-and stress-regulatory hormones aldosterone, AVP and cortisol, as well as thirst , such that hydration is regulated at a lower level until after exercise and/or heat stress (Brandenberger et al 1986;Brandenberger et al 1989). The osmolality and volume effects of hypohydration incur fluid-regulatory responses that could partially mediate the hypervolaemia and improved fluid-regulatory efficiency that is observed with training and heat acclimation adaptations and which helps attenuate cardiovascular strain in exercise (Hopper et al 1988). Further, there are two potential mechanisms explaining PV expansion during heat acclimation.…”

Section: Introductionmentioning

confidence: 99%

Induction and decay of short-term heat acclimation

et al. 2009

View full text Add to dashboard Cite

Abstract:Most advice for heat adaptation is to use long-term (>10 d) regimes, in which hydration status is maintained. We tested the hypothesis that short-term (5-day) heat acclimation would confer substantial improvements in physiological strain and exercise tolerance for exercise in the heat, and fluid regulatory strain provides a thermally-independent stimulus for such adaptations. Ten moderately-fit males were heat acclimated using controlled hyperthermia (rectal temperature 38.5°C) for 90 min on five consecutive days (T a = 40°C, 60% RH), on two occasions separated by a five-week washout, in a randomly assigned, cross-over design; one with euhydration (EUH) and one with dehydration (DEH) during acclimation bouts. One week before, then on the 2 nd day after each acclimation regime, a heat stress test (HST) was completed, comprising cycling at 40% peak power output for 90 min (T a = 35°C, 60% RH), before incrementing to exhaustion. Plasma volume (PV) at rest was measured using CO rebreathing. Acclimation exercise-induced response of[aldo] p became more pronounced across DEH (  178 pg . mL -1 ; 95%CI: 33 to 324) but not EUH (  -47 pg . mL -1 : -209 to 115) and this difference was significant (P=0.02).Compared to EUH, permissive DEH during acclimation bouts conferred larger acclimation-induced increases in resting PV (4.1%: -1.5 to 9.8%; P=0.06), F Q  (4.2: 0.7 to 7.8 ml . min -1. 100 ml -1 ; P=0.009), FVC (0.06: 0.02 to 0.10 ml . 100ml Tissue -1. min -1. mmHg -1 ; P=0.006) and decreased end-exercise c f by 17% (19: -29 to 9 b·min-1; P=0.05). In conclusion, short-term (5-day) heat acclimation was effective with several adaptations more pronounced after fluid-regulatory strain from a dehydration acclimation regime.

show abstract

“…30) Furthermore, in endurance-trained athletes an enhanced diastolic function allows for a more complete filling during the later stages of vigorous exercise. 12) This continuous increase in SV until exhaustion could be explained by a greater left ventricular filling in well-trained athletes, which allows them to increasingly use the Frank-Starling mechanism throughout incremental exercise.…”

Section: Discussionmentioning

confidence: 99%

Effects of Acute Hypoxia at Moderate Altitude on Stroke Volume and Cardiac Output During Exercise

et al. 2010

View full text Add to dashboard Cite

SummaryIt has been unclear how acute hypoxia at moderate altitude affects stroke volume (SV), an index of cardiac function, during exercise. The present study was conducted to reveal whether acute normobaric hypoxia might alter SV during exercise.Nine healthy male subjects performed maximal exercise testing under normobaric normoxic, and normobaric hypoxic conditions (O 2 : 14.4%) in a randomized order. A novel thoracic impedance method was used to continuously measure SV and cardiac output (CO) during exercise.Acute hypoxia decreased maximal work rate (hypoxia; 247 ± 6 [SE] versus normoxia; 267 ± 8 W, P < 0.005) and VO 2 max (hypoxia; 2761 ± 99 versus normoxia; 3039 ± 133 mL/min, P < 0.005). Under hypoxic conditions, SV and CO at maximal exercise decreased (SV: hypoxia; 145 ± 11 versus normoxia; 163 ± 11 mL, P < 0.05, CO: hypoxia; 26.7 ± 2.1 versus normoxia; 30.2 ± 1.8 L/min, P < 0.05). In acute hypoxia, SV during submaximal exercise at identical work rate decreased. Furthermore, in hypoxia, 4 of 9 subjects attained their highest SV at maximal exercise, while in normoxia, 8 of 9 subjects did.Acute normobaric hypoxia attenuated the increment of SV and CO during exercise, and SV reached a plateau earlier under hypoxia than in normoxia. Cardiac function during exercise at this level of acute normobaric hypoxia might be attenuated. (Int Heart J 2010; 51: 170-175) Key words: Normobaric hypoxia, Cardiac output, Oxygen uptake, Exercise testing D uring ascent to a moderate to high altitude, individuals are exposed to progressive decreases in atmospheric pressure that lead to a reduction in inspired, alveolar, and arterial oxygen pressures. Training at moderate altitude (corresponding to 2000 -3000 m) is associated with relatively severe hypoxemia during submaximal and maximal exercise, 1) and acute hypoxia of this level decreases VO 2 max as well as exercise capacity.2-4) Thus, hypoxia at moderate altitude limits training intensity, which leads to relative deconditioning in elite athletes, although endurance athletes often use hypoxic training to improve sea-level performance. 5) Because VO 2 is the product of cardiac output (CO) and the arterio-venous oxygen content difference (C(a-v)O 2 ), a decrease in VO 2 max at maximal exercise may be due to a decrease of either factor, or both.Acute hypoxia may induce abnormalities in cardiac function and redistribution of CO not only at rest but also during exercise. In an animal study, CO at rest increased during acute severe hypoxia (FiO 2 10% and 5%), and blood flow to all organs increased except for the skin and muscle.6) In humans under acute hypoxia, heart rate (HR) and CO increase while systemic vascular resistance decreases. 7)Echocardiography also reveals altered mitral flow patterns, suggestive of mild LV diastolic dysfunction.8) Subacute hypoxia (FiO 2 12%, simulating an altitude of approximately 4000 m) induced mild diastolic dysfunction in young healthy individuals. 9)Stroke volume (SV) increases as the work rate increases at low to moderate intensity exercise, ...

show abstract

Exercise stroke volume relative to plasma-volume expansion

Cited by 101 publications

References 22 publications

The Management of Heat Stress for the Firefighter: A Review of Work Conducted on Behalf of the Toronto Fire Service

The Management of Heat Stress for the Firefighter: A Review of Work Conducted on Behalf of the Toronto Fire Service

Induction and decay of short-term heat acclimation

Effects of Acute Hypoxia at Moderate Altitude on Stroke Volume and Cardiac Output During Exercise

Contact Info

Product

Resources

About