Physiology & Biochemistry 768 Botek M et al. Vagal Threshold Determination … Int J Sports Med 2010; 31: 768–772 accepted after revision July 20, 2010 Bibliography DOI http://dx.doi.org/ 10.1055/s-0030-1263141 Published online: September 10, 2010 Int J Sports Med 2010; 31: 768–772 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Michal Botek, PhD Center for Kinanthropology Research Faculty of Physical Culture T ř . Míru 115 771 40 Olomouc Czech Republic Tel.: + 420/777/277 086 Fax: + 420/585/423 090 michal.botek@upol.cz Key words ● ▶ parasympathetic activity ● ▶ spectral analysis of heart rate variability ● ▶ exercise intensity Vagal Threshold Determination. Effect of Age and Gender entailed with elevated sympathoadrenal activity during exercise should perform exercise at inten- sity up to T VA to avoid the risk of sudden cardiac death. Unfortunately, there is no general consen- sus on its level [6, 8, 21]. Therefore, the primary aim of this study was to develop a new original algorithm for the T VA determination. Since at rest VA is affected among others by age [5] and gen- der [19], we also ascertained the effects of these variables on T VA level. Methods ▼ Participants 40 healthy and physically fit subjects volunteered to participate in this study. They were non-smok- ers and none of the participants were taking any medications. The volunteers were divided into 4 groups (G 1, 2, 3, 4 ) according to age and gender. Characteristics of the subjects are presented in ● ▶ Table 1. The study was performed in con- formity with the ethical guidelines [7] and was approved by the Ethics Committee of Faculty of Physical Culture Palacky University. The subjects submitted their written informed consent. Introduction ▼ A spectral analysis (SA) of the heart rate variabil- ity (HRV) has been shown to be a simple non- invasive method for assessing the autonomic nervous system (ANS) activity by the quantifica- tion of RR intervals variations [1]. A high-fre- quency (HF) peak, or respiratory sinus arrhythmia, has been known to result from respiratory- related vagal modulation of heart rate (HR) [20]. Physical exercise affects the balance between both branches of the ANS which predominantly regulates the HR. The rise in HR has been attrib- uted to vagal withdrawal at low to moderate exercise intensity (EI) [15]. The further incre- ment in HR is affected by the rise in sympathoad- renal activity [14]. Reduced cardiac vagal activity (VA) coupled with an elevated cardiac sympa- thetic activation has been associated with an increased risk of malignant ventricular arrhyth- mias, electrical instability of the heart, and sud- den cardiac death [2, 22]. HR at the point when a disappearance in vagal activity (VA) occurred during a growing EI is called the vagal threshold (T VA ) [17]. We assume that subjects who have the greatest propensity for health complications Authors M. Botek 1 , P. Stejskal 2 , J. Krejci 3 , A. Jakubec 2 , A. Gaba 2 Affiliations 1 Center for Kinanthropology Research, Faculty of Physical Culture, Palacky University Olomouc, Czech Republic 2 Department of Functional Anthropology and Physiology, Faculty of Physical Culture, Palacky University Olomouc, Czech Republic 3 Department of Biomechanics and Engineering Cybernetics, Faculty of Physical Culture, Palacky University Olomouc, Czech Republic Abstract ▼ Progressive increases in exercise intensity cause significant decreases in vagal activity (VA) until a critical point called the vagal threshold (T VA ) is reached. This is where further increases in exer- cise intensity cause negligible change in VA. This study was designed to develop the algorithm for the T VA determination and to assess the effects of age and gender on its level. The sample con- sisted of 40 subjects who were divided according to age and gender into 4 groups with 10 subjects each: G 1 -Men age 25–31, G 2 -Men age 40–57, G 3 - Women age 24–28, and G 4 -Women age 43–56. The vagal responses were assessed by spectral analysis of the heart rate variability method while walking on a treadmill in a steady-state at intensities of 20–70 % of the maximal heart rate reserve (MHRR). The mean intensity of 45 % MHRR was suggested as the T VA level which is related neither to age nor gender. Heart rate related to T VA (T VA-HR ) was affected by gender. High frequency power at T VA was influenced by age. The T VA-HR was considered to be a promising tool for the prescription of a safe level of physical activity for subjects with higher risks of health complications involving elevated sympathoadre- nal activity during exercise.