Effects of Moderate-intensity Aerobic Cycling and Swim Exercise on Post-exertional Blood ...

133 Pages·2012·2.29 MB·English

Effects of Moderate-Intensity Aerobic Cycling and Swim
Exercise on Post-Exertional Blood Pressure in Healthy,
Young Men and Women
by
Robert Alexander Lakin
A thesis submitted in conformity with the requirements
for the degree of Master of Science
Department of Exercise Sciences
University of Toronto
© Copyright by Robert Alexander Lakin 2012
Effects of Moderate-Intensity Aerobic Cycling and Swim Exercise
on Post-Exertional Blood Pressure in Healthy, Young Men and
Women
Robert Alexander Lakin
Master of Science
Department of Exercise Sciences
University of Toronto
2012
Abstract
Aerobic exercise such as cycling is known to elicit a post-exercise hypotensive (PEH) response.
However, it is not known if swim exercise produces a similar effect in normotensive individuals.
We tested the hypothesis that an acute bout of swimming would elicit a PEH response that is less
compared to an equivalent bout of cycling. 10 trained and 11 untrained normotensive (SBP/DBP
< 120/80 mmHg) individuals (23±1 years) underwent 30 min intensity-matched cycling and
swimming sessions to assess changes in BP and cardiovascular responses. While PEH was
similar between modalities within groups, the magnitude and temporality of change in BP
following swimming was significantly different (p < 0.01) between groups, with untrained
participants showing a significant PEH response. Attenuation of PEH in trained individuals was
reflective of a significant increase in sympathetic outflow and slower vagal reactivation,
suggesting training in an aquatic environment leads to alterations in post-exercise BP regulatory
mechanisms.
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Acknowledgments
I would like to acknowledge my supervisor Dr. Jack Goodman for his guidance and support
throughout the duration of my thesis work. I deeply appreciate his effort in helping me to
develop and apply the skills necessary to effectively carry out my research. To my committee
members, Dr. Scott Thomas and Dr. Cathy Notarius, whose valuable input, assistance and
collaboration was essential to the success of this project.
I would also like to thank my parents for their constant encouragement throughout. I would also
like to acknowledge all of the research help that I received from my lab mates and friends,
especially Sam Esfandiari, Sam Liu, Ryan Seeto, Sagar Rohailla, Graeme Wagner, and Mallory
Hood.
The financial funding from the Glen Carter Fellowship in Exercise Intervention and Disease
Prevention, Ontario Graduate Scholarship, and the Department of Exercise Sciences was
extremely helpful in the pursuit of my academic and research goals and I truly appreciate it.
Lastly, this research could not have been possible without the enthusiastic participants who gave
enormous time and effort and with whom I enjoyed working.
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Table of Contents
Acknowledgments .......................................................................................................................... iii
Table of Contents ........................................................................................................................... iv
List of Tables ............................................................................................................................... viii
List of Figures ................................................................................................................................ ix
List of Appendices .......................................................................................................................... x
Abbreviations ............................................................................................................................ xi

Chapter 1 Introduction ................................................................................................................. 1
1.1 Rationale ............................................................................................................................. 1
1.2 Primary Objective ............................................................................................................... 3
1.3 Secondary Objective ........................................................................................................... 3
1.4 Primary Hypotheses ............................................................................................................ 3

Chapter 2 Literature Review ....................................................................................................... 4
2.1 Blood Pressure Responses during Exercise ........................................................................ 4
2.2 Blood Pressure Response during Endurance Exercise ......................................................... 5
2.3 Acute Exercise and the Blood Pressure Response .............................................................. 6
2.3.1 Effect of Subject Characteristics on PEH ............................................................... 7
2.3.1.1 Gender ..................................................................................................................... 7
2.3.1.2 Training Status ........................................................................................................ 8
2.3.1.3 Age .......................................................................................................................... 8
2.3.1.4 Resting Blood Pressure ........................................................................................... 8
2.3.2 Acute Exercise Intensity, Duration, and PEH ......................................................... 9
2.3.3 Potential Factors Underlying the Observed Differences ...................................... 10
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2.3.4 Mechanisms of Post-Exercise Hypotension .......................................................... 11
2.3.5 Baroreceptor Sensitivity ........................................................................................ 20
2.3.6 Thermoregulation and the Blood Pressure Response ........................................... 24
2.4 Swimming as an Aerobic Exercise Modality .................................................................... 26
2.4.1 Swimming: Metabolic and Cardiorespiratory Responses ..................................... 27
2.4.2 Swimming Exercise and the Blood Pressure Response ........................................ 29
2.4.3 Hemodynamic Responses During and Following Swimming .............................. 32
2.4.4 Mechanisms of Post-Swimming Blood Pressure Response .................................. 35
2.4.5 Baroreceptors ........................................................................................................ 39
2.4.6 Thermoregulation .................................................................................................. 41

Chapter 3 Manuscript for Journal Submission ....................................................................... 43
3.1 Abstract ............................................................................................................................. 43
3.2 Introduction ....................................................................................................................... 43
3.3 Methods ............................................................................................................................. 45
3.3.1 Subjects ................................................................................................................. 45
3.3.2 Study Design ......................................................................................................... 45
3.3.3 Exercise Testing .................................................................................................... 47
3.3.4 Acute Cycling or Swimming Exercise Intervention ............................................. 47
3.4 Measurements ................................................................................................................... 48
3.4.1 Blood Pressure ...................................................................................................... 48
3.4.2 Cardiac Output, Stroke Volume, Total Peripheral Resistance .............................. 49
3.4.3 Skin and Core Body Temperature ......................................................................... 49
3.4.4 Autonomic Function ............................................................................................. 50
3.4.5 Baroreflex Sensitivity ........................................................................................... 50
3.4.6 Respiratory Frequency .......................................................................................... 50
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3.5 Statistical Analysis ............................................................................................................ 51
3.6 Results ............................................................................................................................... 51
3.6.1 Subjects ................................................................................................................. 51
3.6.2 Exercise Stress ...................................................................................................... 52
3.6.2 Post-Exercise Blood Pressure Response ............................................................... 53
3.6.3 Hemodynamics ..................................................................................................... 60
3.6.4 Baroreflex Sensitivity ........................................................................................... 61
3.6.5 Heart Rate Variability ........................................................................................... 63
3.6.6 Respiratory Frequency .......................................................................................... 63
3.6.7 Core and Skin Temperature .................................................................................. 63
3.7 Discussion ......................................................................................................................... 65
3.7.1 PEH response to Exercise in Untrained Subjects ................................................. 65
3.7.2 Influence of Exercise Training on PEH Responses .............................................. 67
3.7.3 Influence of Training Status on PEH Responses: Group Analysis ....................... 68
3.8 Limitations ........................................................................................................................ 70
3.9 Conclusion ........................................................................................................................ 70

Chapter 4 General Discussion, Future Directions, and Conclusions ..................................... 72
4.1 Subjects ............................................................................................................................. 72
4.2 Alternative Mechanisms, Limitations, and Future Directions .......................................... 72
4.2.1 Alternative Mechanisms ....................................................................................... 72
4.2.2 Limitations ............................................................................................................ 76
4.2.3 Future Directions .................................................................................................. 77
4.3 Conclusions ........................................................................................................................ 77

References ..................................................................................................................................... 79
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Appendix A: Supplementary Review ..................................................................................... 104
A.1 Review of the Finometer Measures ................................................................................. 104
A.2 Review of Baroreflex Sensitivity .................................................................................... 105
A.3 Review of Arterial Stiffness ............................................................................................ 106
A.4 Review of Water-Based Exercise Intensity Measures .................................................... 108
A.5 Review of Core and Skin Temperature Measurements ................................................... 109
Appendix B: Consent Form ................................................................................................... 111
Appendix C: Par-Q ................................................................................................................. 116
Appendix D: Recruitment Poster ........................................................................................... 118
Appendix E: Protocol for Acute Exercise Assessment .......................................................... 119
Copyright Acknowledgements ............................................................................................... 121

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List of Tables
Table 3.1: Baseline subject characteristics .................................................................................. 52
Table 3.2: Immediate post-exercise systolic and diastolic blood pressures……………………. 53
Table 3.3: Changes in systolic and diastolic blood pressure from pre-exercise throughout
recovery…………………………………………………………………………………………. 55
Table 3.4 Significant correlations between ∆SBP and predictor variables……………………...56
Table 3.5: Changes in hemodynamics from pre-exercise following acute exercise………...…..61
Table 3.6: Baroreflex sensitivity and heart rate variability following acute exercise...………... 62
Table 3.7: Core and skin temperature changes following acute exercise…...…………………. 64

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List of Figures

Figure 2.1 Schematic overview of hemodynamic changes during post-exercise hypotension in
comparison with the resting state……………………………………………………………...…12
Figure 2.2 Schematic overview of neural and local control of vascular tone related to post-
exercise hypotension…………………………………………………………………………..…18
Figure 2.3 A schematic illustration of the baroreflex stimulus-response curve…………………22
Figure 3.1 Timeline of pre- and post-exercise measurements during the acute cycle and swim
exercise protocols………………………………………………………………………………..46
Figure 3.2 Change in systolic blood pressure to acute cycling and swimming in untrained
individuals………………………………………………………………………………………. 57
Figure 3.3 Change in systolic blood pressure to acute cycling and swimming in trained
individuals………………………………………………………………………………………. 57
Figure 3.4 Change in systolic blood pressure from baseline following acute swimming exercise
in trained and untrained groups.………………………………………………………………….58
Figure 3.5 Changes in diastolic blood pressure from pre-exercise levels following acute
swimming exercise in trained and untrained groups.…………………………………………….58
Figure 3.6 Relationship between the magnitude of change in systolic blood pressure (SBP) after
acute swimming and aerobic fitness level (VO ) at 25 min post-exercise……………………59
2max
Figure 3.7 Relationship between the magnitude of change in systolic blood pressure (SBP) after
acute swimming and aerobic fitness level (VO ) at 50 min post-exercise…………………...59
2max
Figure 3.8 Relationship between the magnitude of change in systolic blood pressure (SBP) after
acute swimming and aerobic fitness level (VO ) at 75 min post-exercise…………………....60
2max
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List of Appendices
Appendix A: Supplementary Review ……………………………………………………..…..104
Appendix B: Consent Form …………………………………………………………………...111
Appendix C: Par-Q …………………………………………………………...……………… 116
Appendix D: Recruitment Poster ………………………………………………...…………... 118
Appendix E: Protocol for Acute Exercise Assessment ……………………...………………. 119

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