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image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Applied Physiology N...arrow_drop_down
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
Applied Physiology Nutrition and Metabolism
Article . 2015
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Reply to “Discussion: ‘Cardiorespiratory alterations induced by low-intensity exercise performed in water or on land’ – What hemodynamic changes during cycling in water?”

Authors: Olivier, Gavarry; Guillaume, Chaumet; Alain, Boussuges;

Reply to “Discussion: ‘Cardiorespiratory alterations induced by low-intensity exercise performed in water or on land’ – What hemodynamic changes during cycling in water?”

Abstract

We thank Dr Gayda and colleagues (Gayda et al. 2015) for their comments on our article, which was recently published in Applied Physiology, Nutrition, and Metabolism (Ayme et al. 2015). Gayda et al. underline the problem of the assessment of the exercise intensity during cycling in water. The aim of our study was to compare the cardiorespiratory alterations induced by low-intensity exercise performed on land or in water. Our results reported similar hemodynamic status during the 2 sessions. In contrast, changes in breathing pattern were in favor of an increase in the work of breathing in water. These results contrasted with the recent findings of Garzon et al. (2015a). In their study, they reported a decrease in oxygen uptake and arterial-venous oxygen content difference and an increase in stroke volume and cardiac output during cycling in water when compared with cycling on land. Several factors could explain the discrepancies between these 2 studies, such as position of the volunteers, exercise modalities, methods of measurement of cardiac output, and assessment of exercise intensity. As underlined by Gayda et al. (2015), in their comment, the load induced by exercising in water is difficult to assess. The density of water is approximately 800 times that of air and the increase in resistance induced by the water leads to an increase in the workload when pedalling in water in comparison with on land. In our study, to adequately compare the 2 exercise bouts we have chosen to control the energy expenditure. The volunteers spent the 2 experimental sessions (on land or in head-out water immersion) in the same sitting position. The subjects sat in a tank containing a submersible mechanical ergometer designed by our team (Fig. 1) and used in a previous experiment (Boussuges et al. 2007). A same pedalling rate was used by the volunteers during the 2 exercise bouts (47 ± 4 revolutions per minute (r·min–1)). The level of energy expenditure was determined using a maximal incremental exercise previously performed and corresponded to 35%–40% of peak oxygen uptake. During the sessions, the volunteers began cycling without load and the external load was adjusted, during the first minutes, to reach the oxygen uptake (VO2) determined by the incremental exercise in absolute value (16.5 mL·kg–1·min–1 in mean). Thereafter, the VO2 was continuously monitored using breath-by-breath metabolic system to maintain constant the energy expenditure. Investigations were performed during steadystate exercise at 45 min after the beginning of the exercises. In the study performed by Garzon et al. (2015a), the exercise was incremental with a load increase every 1 min. Using this procedure, no steady-state in hemodynamic status could be expected. In the Brechat study (Brechat et al. 2013), cited by Gayda et al. (2015) in their letter to the Editor, hemodynamic variables reached steady-state 3 to 5min after the beginning of cycling exercise both on land and in water. Interestingly, their observations were similar to ours and disagreed with the results of Garzon et al. (2015a). Indeed, heart rate, stroke volume, cardiac index, and blood pressure recorded during 30-min cycling exercises performed at similar VO2 (60% of maximal oxygen uptake), were not significantly different in air or inwater. In the study of Garzon et al. (2015a), the pedalling rate was different in the 2 sessions on land and in water. An impact of the pedalling rate on VO2 has been demonstrated (Chavarren and Calbet 1999). To overcome this limit and estimate VO2 during cycling in water, the authors have used a prediction equation based on pedalling rate (Garzon et al. 2015a). It might be an interesting tool to prescribe for immersed exercise. Nevertheless, in the present form, its interest remains doubtful. Indeed, the authors have performed previous studies to elaborate and validate and used their equation (Garzon et al. 2015b; Leone et al. 2014). According to the Bland and Altman plot (Garzon et al. 2015a), their limits of agreement in the estimation of the workload vary from –32.7 W to +36 W. This discrepancy is considerable and impairs the interest of the prediction equation in physiological studies. Moreover, the use of the prediction equation in clinical practice can lead to the prescription of an unsuitable workload, which may be dangerous in some patients, such as patients suffering from cardiac disease. Finally, to assess the hemodynamic alterations induced by exercise, we have used Doppler echocardiography. Stroke volume was determined from the combination of the aortic crosssectional area measured by 2-dimensional echocardiography and the aortic blood flow recorded on the same site by continuouswave Doppler. The reliability of this method has been demonstrated (Rowland andObert 2002). In our work, stroke volumewas not significantly different during ergocycling in water and on land. Gas expiratory parameters analysis agreed with this result. Indeed, oxygen pulse, used as an index of stroke volume, was similar between the 2 sessions. To study hemodynamic changes induced by cycling, Garzon et al. (2015a) have used impedance cardiography. This method has been previously used to assess cardiac output in subjects at rest or during exercise on land. Nevertheless, the accuracy of impedance cardiography remains questioned by recent works (Bogui et al. 2013; de Waal et al. 2008; Taylor et al. 2012). Furthermore, the water content of various sectors (intravascular but also interstitial

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Subjects by Vocabulary

Microsoft Academic Graph classification: Cardiac output medicine.medical_specialty Oxygen pulse Incremental exercise Medicine medicine.diagnostic_test business.industry VO2 max Cardiorespiratory fitness Stroke volume Impedance cardiography Exercise intensity Physical therapy business

Keywords

Male, Physiology, Endocrinology, Diabetes and Metabolism, Respiratory System, Cardiovascular System, Physiology (medical), Humans, Exercise, Nutrition and Dietetics, General Medicine

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    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Average
    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
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