303 List of Abbreviations ATP Adenosine triphosphate ART Assisted reproductive technologies CRH Corticotropin-releasing hormone ERK Extracellular-signal-regulated kinases FSH Follicle-stimulating hormone GnRH Gonadotropin-releasing hormone HPT Hypothalamus–pituitary–testis JNK C-Jun N-Terminal Kinases LH Luteinizing hormone MAPK Mitogen-activated protein Kinases MDA Malondialdehyde OS Oxidative stress PUFA Polyunsaturated fatty acids 18 Oxidative Stress and Infertility: A Possible Link to Exercise Pieter Johann Maartens, Jason Peng, Ashok Agarwal, Diana Vaamonde and Stefan S. du Plessis © Springer Science+Business Media New York 2016 D. Vaamonde et al. (eds.), Exercise and Human Reproduction, DOI 10.1007/978-1-4939-3402-7_18 S. S. du Plessis () Division of Medical Physiology, Department of Biomed- ical Sciences, Stellenbosch University, P.O. Box 19063, Tygerberg 7505, Cape Town, South Africa e-mail: ssdp@sun.ac.za P. J. Maartens Division of Medical Physiology, Faculty of Medicine and Health Sciences, Stellenbosh University, Cape Town, Tygerberg, South Africa J. Peng Center for Reproductive Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA A. Agarwal American Center for Reproductive Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA D. Vaamonde Department of Morphological Sciences, School of Medicine, Gynemed and Reproductive Care Center, University of Cordoba, International Network on Physical Exercise and Fertility (INPEF), Cordoba, Spain e-mail: fivresearch@yahoo.com RNS Reactive nitrogen species ROS Reactive oxygen species SHBG Sex-hormone-binding globulin Introduction Infertility can be defined as the reduction in or absence of the capacity of a man and/or a woman to reproduce [1]. The term is generally used to reference the reproductive state of a couple who are sexually active without the use of contracep- tives and yet are unable to achieve spontaneous natural pregnancy after a year of attempt. Both male and female reproductive impediments can contribute to infertility, and approximately 15 % of the population in high-income countries and between 9 and 30 % in low-income countries are affected [2–4]. One of the biggest issues remains that of the idiopathic component of infertility and the extent to which various lifestyle factors, such as exercise, possibly affect this phenomenon [5]. Oxidative stress (OS) is defined as an imbal- ance of reactive oxygen species (ROS) produc- tion and the detoxification of these molecules by antioxidative processes in the body. Antioxidants have a protective effect acting as scavengers of surplus ROS, and thus any external influence that can disturb this delicately balanced homeostasis is regarded a threat to the health of individuals [6–9]. ROS are free radicals that are natural by- products of energy production and cellular me- tabolism. Interestingly enough, they are required in physiological amounts as second messengers