The effects of antioxidant supplementation on exercise-induced oxidative stress in cyclists

222 Pages·2017·2.19 MB·English

by  Matthew Soden

The effects of antioxidant supplementation on exercise-induced
oxidative stress in cyclists

by
Matthew Soden

A thesis submitted to
The University of Birmingham
For the degree of
DOCTOR OF PHILOSOPHY

School of Sport, Exercise & Rehabilitation Sciences
College of Life and Environmental Sciences
The University of Birmingham
March 2017
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Abstract
Exercise is inherently linked with the production of reactive oxygen and nitrogen
species (RONS), which are able to elicit an effect on cellular redox status and may augment
oxidative stress post-exercise. Antioxidant supplements have the potential to reduce exercise-
induced oxidative stress, and interact with redox status but in doing so they may have a
negative effect on exercise adaptations associated with RONS mediated signalling pathways.
This thesis presents novel findings on the consumption habits of antioxidant supplements in
amateur cyclists and the effect of habitual supplementation on exercise-induced oxidative
stress following a cycling sportive in recreational cyclists (chapters 2 and 3). The thesis goes
on to assess the effect of habitual supplementation on basal levels of endogenous antioxidant
proteins and the exercise-induced oxidative stress response to steady-state cycling in trained
cyclists (chapter 4), and the effects of polyphenol supplementation on cycling recovery and
subsequent day cycling performance, assessed via markers of oxidative stress, inflammation,
and a time-trial in trained cyclists (chapter 5). Consumption of antioxidant supplements was
reported in 40% of the participants sampled and was not associated with age, cycling
experience or weekly training hours. The main reasons given for antioxidant supplementation
were to: improve immunity; recovery; and performance. Upon completion of 100 km of
cycling, antioxidant supplementation did not attenuate exercise-induced oxidative markers
compared to a non-supplemented group. Both groups displayed augmented oxidative stress
after cycling 100 km. In trained cyclists, habitual supplementation did not result in any
differences in resting concentrations of the endogenous antioxidants superoxide dismutase-1
(SOD1), superoxide dismutase-2 (SOD2) or glutathione peroxidase-1 (GPx-1); nor the
oxidative stress response to steady-state cycling. Supplementation with a polyphenol based
drink had no effect on exercise-induced oxidative stress and inflammation markers at any
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time-point compared to a placebo control drink. Furthermore, supplementation during the
recovery period (24 hours) did not provide an ergogenic when undertaking a cycling time-
trial in trained cyclists. In conclusion, the results obtained in this thesis do not support a
beneficial role for the habitual consumption of commercially available antioxidant
supplements in cyclists. No attenuation in exercise-induced oxidative stress in a ‘real-world’
or laboratory setting was observed compared to non-supplemented individuals. Furthermore,
additional education may be required for cyclists to enhance their knowledge on the
interactions of antioxidant supplements. The reasons given by cyclists for antioxidant
consumption were not supported by the current research.

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Acknowledgements
Unlike the thesis, my acknowledgments will be short and sweet. This achievement
would not have been possible without the constant support from my loving family and
friends. It was never going to be an easy journey, but at the same time, who could have
conceptualised how difficult this was going to be. However, through the setbacks and
disappointments, this thesis has finally come to fruition.
Remarkable things are always achieved as a collective. And I would like to give a
special appreciation to the people behind the scenes who have made this possible. These
individuals deserve to be recognised because they have had to deal with the rollercoaster ride
over the last several years. On that note, I would like to give my sincerest thanks and
gratitude to my mother, Teresa Soden, for her eternal belief and constant support throughout
this process. You have experienced the highs and the lows, and it is impossible for me to put
into words how appreciative I am for the sacrifices you have made to help me obtain my
doctorate. Without your support, not just over the last few years, but throughout the whole of
my academic life I would not be where I am today. Additionally, a huge thank you goes to
Suzanne and Nolan Shinn. The two of you gave me the initial confidence to pursue a degree
and look where it has led! Thanks for helping turn my life around for the better, you are both
amazing friends whom I consider more like family.
To my supervisors, Sarah and Gareth thank you for your backing and advice. Sarah,
thank you for believing in me as an undergraduate and for providing me with this
opportunity. I will forever be grateful. Gareth, thank you for your support and encouragement
along the way, both inside and outside of the laboratory, and for always having your door
open for a chat. I hope in the near future we will have the opportunity to work with one
another again.
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I would like to thank members of the Exercise Metabolism Research Group for being
an amazing group of people, who would always be on hand to discuss and solve any
problems. It has been an immense pleasure working with each and every one of you. A big
appreciation goes out to my fellow postgraduates and staff members who have made this
experience extremely pleasurable. Additionally, thanks to every participant who volunteered
their time, blood, muscle and sweat to my research, the Marie Curie Hospice in Solihull, and
the organisers of the Wiggle Dragon Ride and the Tommy Godwin cycling sportive; without
your assistance this thesis would have never come to fruition.

I would like to dedicate this thesis to my Dad. I know you would be so
proud to share this accomplishment with me.

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List of Contents
Chapter One
General Introduction 1
1.1 Introduction 2
1.2 Oxidative Stress 5
1.2.1 Free Radicals 5
1.2.2 Reactive oxygen species and nitrogen species 7
1.3 Antioxidants 9
1.3.1 Overview 9
1.3.2 Endogenous antioxidants 9
1.3.3 Exogenous Antioxidants 10
1.4 Exercise and Oxidative Stress 13
1.4.1 Sources of RONS during skeletal muscle contractions 13
1.4.2 RONS are involved in exercise adaptations 14
1.4.3 Factors influencing oxidative stress post-exercise 15
1.4.4 Antioxidant response to exercise 18
1.4.5 Relationship between exercise-induced inflammation and oxidative stress 19
1.4.6 Methodological Limitations of Assessing Markers of Oxidative Stress 21
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1.5 Exercise and Antioxidant Supplementation 25
1.5.1 Impact of antioxidant supplementation on RONS mediated signalling post-
exercise 25
1.5.2 Polyphenol supplementation on exercise-induced oxidative stress and
inflammation 29
1.5.3 Polyphenol supplementation on exercise recovery and subsequent days
performance 34

1.6 Aims of the thesis 37

Chapter Two
The prevalence of antioxidant supplementation in amateur cyclists
undertaking the Wiggle Dragon Ride 39
2.1 Abstract 40
2.2 Introduction 41
2.3 Methods 45
2.4 Results 47
2.5 Discussion 54

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Chapter Three
Habitual antioxidant supplementation does not affect the oxidative stress
response after a 100 km cycling sportive 63
3.1 Abstract 64
3.2 Introduction 65
3.3 Methods 68
3.4 Results 74
3.5 Discussion 80

Chapter Four
Habitual antioxidant supplementation does not affect resting levels of
endogenous antioxidants or the oxidative stress response to steady-state
cycling 84
4.1 Abstract 85
4.2 Introduction 86
4.3 Methods 90
4.4 Results 100
4.5 Discussion 106

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Chapter Five
Supplementation with a Montmorency Tart Cherry drink in trained
cyclists does not reduce exercise-induced oxidative stress or improve
subsequent days cycling time-trial performance: a placebo crossover design
study 112
5.1 Abstract 113
5.2 Introduction 114
5.3 Methods 116
5.4 Results 126
5.5 Discussion 137

Chapter Six
General discussion 147
6.1 Summary 148
6.2 Habitual consumption of antioxidant supplements 148
6.3 Habitual antioxidant supplementation on exercise-induced oxidative stress 150
6.4 Impact of Montmorency Tart cherry supplementation on cycling recovery
and performance 151
6.5 Conclusions 152
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