# The Effect of Aromatherapy on Post-Exercise Hypotension: A Pilot Study
## 1 Introduction  
Hypertension, defined as persistently elevated blood pressure (BP), is a major global health concern that contributes significantly to the burden of cardiovascular diseases [1]. The global population with hypertension is steadily increasing, exceeding one billion individuals; thus, hypertension has become a critical public health challenge [2]. According to the United States Centers for Disease Control and Prevention [3], the prevalence of hypertension among adults aged 18 and older was 47.7% between August 2021 and August 2023. Furthermore, accumulated data have demonstrated that the prevalence of hypertension in young individuals is increasing [4]. It was reported that the prevalence of hypertension among adults aged 18-39 years is 30.0% in men and 16.4% in women [3]. [PERSON] et al. suggested that this increase can be attributed to unhealthy lifestyle habits and the obesity epidemic [5]. Regular exercise is the most effective non-pharmacological approach to managing BP [6]. Post-exercise hypotension (PEH) refers to a temporary reduction in BP below resting levels that occurs during the recovery period following acute exercise. Particularly for hypertensive individuals, the cumulative effects of repeated PEH induced by regular exercise, referred to as training effects, can eventually lead to sustained reductions in BP [7]. Studies have demonstrated that PEH lasts 10-170 min after 20-60 min of exercise, depending on the type, length, and intensity of the physical activity [8]. Specifically, aerobic exercise elicits a greater PEH effect than resistance exercise [9]. Moreover, moderate-intensity aerobic exercise at 60% maximum oxygen consumption (VO\({}_{2}\)max) induces a more pronounced PEH response than low-intensity aerobic exercise at 40% VO\({}_{2}\)max [9]. Aromatherapy, which involves the use of aromatic plant extracts for therapeutic purposes, has gained traction as a complementary approach to improve various aspects of health, particularly cardiovascular responses such as BP and heart rate (HR), through the inhalation of essential oil fragrances [10]. Aromatherapy for patients with hypertension has been demonstrated to reduce BP and stress [11], as well as blood epinephrine and cortisol levels [12]. The mechanism underlying these effects involves the absorption of inhaled aroma oil particles by the olfactory nerve cells through the cilia located on the ceiling of the nasal cavity. These stimulations can be transmitted to the brain through the limbic system of the cerebrum. From the limbic system, the signals are relayed to the hypothalamus, which then communicates with the autonomic nervous system (ANS) and pituitary gland to regulate hormones [13]. Consequently, the aromatherapy-induced reduction in sympathetic nerve activity (SNA) and increase in parasympathetic nerve activity (PNA) can impact BP [14]. Activation of the limbic system with essential oil inhalation may also increase dopamine release, which is associated with pleasure and relaxation, thereby affecting BP [15]. Moreover, studies have suggested that aromatherapy can assist in the treatment of physical ailments by modulating the endocrine and immune systems and directly affects vascular function [16; 17]. Given the previous studies demonstrating that aromatherapy alleviates BP, it can be speculated that aromatherapy can further enhance PEH, potentially influencing the magnitude and duration of the condition. However, the effect of aromatherapy on BP during the post-exercise period remains unexplored. Therefore, as a pilot study, we hypothesized that aromatherapy following exercise exaggerates the PEH response. The purpose of this study was not only to expand our understanding of the physiological effects of aromatherapy on BP but also to provide preliminary evidence for novel and integrative approaches to enhance the post-exercise reduction in BP.