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Measurement of Cardiac Output in Children during Exercise: A Review

David J. Driscoll, Bruce A. Staats, and Kenneth C. Beck

Knowledge of cardiac output changes during exercise is helpful for understanding normal exercise physiology and the effect of disease upon exercise performance. There are four noninvasive techniques applicable to measurement of cardiac output in children: Indirect Fick, acetylene rebreathing, electrical bioimpedance, and Doppler. Each technique requires substantial operator experience to obtain reliable and reproducible results.

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Test-Retest Reproducibility of Submaximal and Maximal Cardiac Output by Doppler Echocardiography and CO2-Rebreathing in Prepubertal Children

Stéphane Nottin, Agnès Vinet, Anne-Marie Lecoq, Patrick Guenon, and Philippe Obert

The aim of this study was to examine the reproducibility of cardiac output (Q) measured by Doppler echocardiography and CO2-rebreathing in prepubertal children during exercise. Fourteen healthy children (8 girls and 6 boys aged 10.9 ± 0.9 years) underwent a progressive maximum upright cycle test until exhaustion on two separate occasions (1 week apart). Q was determined successively by the two methods at rest and during the final minutes of each workload. The reproducibility of the Doppler method was higher than the reproducibility of the CO2-rebreathing method, both at rest and during exercise. Moreover, this reproducibility was lower during high intensity exercise whatever the method used. On account of its high reproducibility, Doppler echocardiography should be preferentially used to detect changes in Q as a result of an exercise training intervention in prepubertal children.

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The Decremental Protocol as an Alternative Protocol to Measure Maximal Oxygen Consumption in Athletes

Katrina Taylor, Jeffrey Seegmiller, and Chantal A. Vella

Purpose:

To determine whether a decremental protocol could elicit a higher maximal oxygen consumption (VO2max) than an incremental protocol in trained participants. A secondary aim was to examine whether cardiac-output (Q) and stroke-volume (SV) responses differed between decremental and incremental protocols in this sample.

Methods:

Nineteen runners/triathletes were randomized to either the decremental or incremental group. All participants completed an initial incremental VO2max test on a treadmill, followed by a verification phase. The incremental group completed 2 further incremental tests. The decremental group completed a second VO2max test using the decremental protocol, based on their verification phase. The decremental group then completed a final incremental test. During each test, VO2, ventilation, and heart rate were measured, and cardiac variables were estimated with thoracic bioimpedance. Repeated-measures analysis of variance was conducted with an alpha level set at .05.

Results:

There were no significant main effects for group (P = .37) or interaction (P = .10) over time (P = .45). VO2max was similar between the incremental (57.29 ± 8.94 mL · kg–1 · min–1) and decremental (60.82 ± 8.49 mL · kg–1 · min–1) groups over time. Furthermore, Q and SV were similar between the incremental (Q 22.72 ± 5.85 L/min, SV 119.64 ± 33.02 mL/beat) and decremental groups (Q 20.36 ± 4.59 L/min, SV 109.03 ± 24.27 mL/beat) across all 3 trials.

Conclusions:

The findings suggest that the decremental protocol does not elicit higher VO2max than an incremental protocol but may be used as an alternative protocol to measure VO2max in runners and triathletes.

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Cardiovascular and Metabolic Responses to On-Water Upwind Sailing in Optimist Sailors

Santiago Lopez, Jan G. Bourgois, Enrico Tam, Paolo Bruseghini, and Carlo Capelli

Purpose:

To explore the cardiovascular and metabolic responses of 9 Optimist sailors (12.7 ± 0.8 y, 153 ± 9 cm, 41 ± 6 kg, sailing career 6.2 ± 1 y, peak oxygen uptake [V̇O2peak] 50.5 ± 4.5 mL · min−1 · kg−1) during on-water upwind sailing with various wind intensities (W).

Methods:

In a laboratory session, peak V̇O2, beat-by-beat cardiac output (Q̇), mean arterial blood pressure (MAP), and heart rate (f H) were measured using a progressive cycle ramp protocol. Steady-state V̇O2, Q̇, MAP, and f H at 4 submaximal workloads were also determined. During 2 on-water upwind sailing tests (constant course and with tacks), W, Q̇, MAP, and f H were measured for 15 min. On-water V̇O2 was estimated on the basis of steady-state f H measured on water and of the individual ΔV̇O2f H relationship obtained in the laboratory.

Results:

V̇O2, f H, and Q̇ expressed as percentage of the corresponding peak values were linearly related with W; exercise intensity during on-water sailing corresponded to 46–48% of V̇O2peak. MAP and total vascular peripheral resistance (TPR = MAP/Q̇) were larger (P < .005) during on-water tests (+39% and +50%, respectively) than during cycling, and they were correlated with W. These responses were responsible for larger values of the double (DP) and triple (TP) products of the heart during sailing than during cycling (P < .005) (+37% and +32%, respectively).

Conclusions:

These data indicate that the cardiovascular system was particularly stressed during upwind sailing even though the exercise intensity of this activity was not particularly high.

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High-Resolution Dynamics of Hemodilution After Exercise-Related Hemoconcentration

Zsolt Komka, Brigitta Szilágyi, Dóra Molnár, Bence Sipos, Miklós Tóth, János Elek, and Máté Szász

reserve for the body, this mechanism can also contribute to systemic hemoconcentration. 7 – 9 Hemoconcentration develops during exercise when the increased cardiac output is associated with a higher flow rate and a significant shear stress of the endothelium. Elevated hematocrit (Hct) and viscosity of

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Implication of Blood Rheology and Pulmonary Hemodynamics on Exercise-Induced Hypoxemia at Sea Level and Altitude in Athletes

Antoine Raberin, Elie Nader, Jorge Lopez Ayerbe, Patrick Mucci, Vincent Pialoux, Henri Meric, Philippe Connes, and Fabienne Durand

incomplete red blood cell (RBC) oxygenation caused by the decrease in RBC transit time in alveoli capillaries occurring with the rise in cardiac output ( Q ˙ c ) during exercise and/or to an inability of O 2 to diffuse across thickened alveolar-capillary membranes ( Hodges et al., 2006 ). The high elevation

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Bringing Light into the Dark: Effects of Compression Clothing on Performance and Recovery

Dennis-Peter Born, Billy Sperlich, and Hans-Christer Holmberg

To assess original research addressing the effect of the application of compression clothing on sport performance and recovery after exercise, a computer-based literature research was performed in July 2011 using the electronic databases PubMed, MEDLINE, SPORTDiscus, and Web of Science. Studies examining the effect of compression clothing on endurance, strength and power, motor control, and physiological, psychological, and biomechanical parameters during or after exercise were included, and means and measures of variability of the outcome measures were recorded to estimate the effect size (Hedges g) and associated 95% confidence intervals for comparisons of experimental (compression) and control trials (noncompression). The characteristics of the compression clothing, participants, and study design were also extracted. The original research from peer-reviewed journals was examined using the Physiotherapy Evidence Database (PEDro) Scale. Results indicated small effect sizes for the application of compression clothing during exercise for shortduration sprints (10–60 m), vertical-jump height, extending time to exhaustion (such as running at VO2max or during incremental tests), and time-trial performance (3–60 min). When compression clothing was applied for recovery purposes after exercise, small to moderate effect sizes were observed in recovery of maximal strength and power, especially vertical-jump exercise; reductions in muscle swelling and perceived muscle pain; blood lactate removal; and increases in body temperature. These results suggest that the application of compression clothing may assist athletic performance and recovery in given situations with consideration of the effects magnitude and practical relevance.

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No Effects of Different Doses of New Zealand Blackcurrant Extract on Cardiovascular Responses During Rest and Submaximal Exercise Across a Week in Trained Male Cyclists

Stefano Montanari, Mehmet A. Şahin, Ben J. Lee, Sam D. Blacker, and Mark E.T. Willems

During endurance exercise, the increment in oxygen consumption is predominantly dictated by the metabolic demand of skeletal muscles. Cardiac output (CO) increases to meet the oxygen demand during endurance exercise ( Hellsten & Nyberg, 2016 ). Elite athletes can sustain a high-intensity workload

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Individualizing Basketball-Specific Interval Training Using Anaerobic Speed Reserve: Effects on Physiological and Hormonal Adaptations

Chenhang Wang and Mingliang Ye

a graded exercise test to evaluate V ˙ O 2 max , MAS, V ˙ O 2 / HR (O 2 pulse), first (VT 1 ), and second (VT 2 ) ventilatory threshold. Stroke volume (SV) and cardiac output ( Q ˙ max ) were also evaluated during the graded exercise test. The lower-body Wingate test analyzed the individual

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Energy Cost of Running in Well-Trained Athletes: Toward Slope-Dependent Factors

Marcel Lemire, Romain Remetter, Thomas J. Hureau, Bernard Geny, Evelyne Lonsdorfer, Fabrice Favret, and Stéphane P. Dufour

ECR during level running (LR), 2 but the implication of the pulmonary (tidal volume and respiratory frequency) and cardiovascular determinants (heart rate [HR], stroke volume [SV], cardiac output [ Q ˙ ], arteriovenous O 2 difference [ a – v ¯ O 2 ]) of O 2 transport have never been investigated