1
Orignal Article
Role of Waist-to-Height Ratio on Percent Recovery Heart Rate in Young Adult Males of Bijapur, Karnataka (India).
Haroonrashid M. Hattiwale, Shaheenkousar H. Hattiwale, Salim A. Dhundasi and
Kusal K. Das*
Department of Physiology, Al Ameen Medical College, Bijapur-586108, Karnataka, India
Running title: WHtR % Recovery Heart Rate Bijapur
*All Correspondence:
Prof.Kusal K.Das
Professor,
Department of Physiology,
Al-Ameen Medical College,
Bijapur-586108,
Karnataka state, India.
Tel: (W) 91-8352-272502
(R) 91-8352-272067
Fax: 91-8352-270184
Email:
Abstract
Objectives: This study was designed to evaluate the influence of body mass index and waist to height ratio which are known predictors of cardiovascular diseases, with % recovery heart rate in male adult subjects of Bijapur, Karnataka, India. Methods: 52 adult males belonging to mean age group of 24.16 + 8.12 were selected as subjects from the general population of north Karnataka, randomly for this study. The BMI, W/Ht and WHR were calculated. Subjects performed submaximal exercise test by using cycle ergometer. Heart rate and blood pressure were measured before exercise (pre-exercise), immediately after exercise (peak-exercise) and 2 minutes after cessation of exercise (post-exercise) and percent recovery of heart rate was calculated. Results: There was a statistically significant positive correlation between BMI, waist hip ratio, waist to height ratio with mean arterial pressure, and a significant negative correlation was found between waist to height ratio and percent recovery heart rate. Conclusions: Our study concludes that WHtR may be considered as an important anthropometrical tool which correlates with cardiovascular fitness among young male adults of Bijapur. This anthropometrical parameter may also be used to evaluate metabolic syndrome or insulin resistance diabetic status of an individual.
Key words: Heart rate recovery, mean arterial blood pressure, BMI, waist to hip ratio, waist to height ratio
1. Introduction
Obesity is a rapidly growing health problem across the globe. WHO warns that the greater future burden of obesity and diabetes will affect developing and tropical countries, within the next 2 decades. The body mass index (BMI), or Quetelet index, the best proxy for body fat percentage among ratios of weight and height. Elevated body mass index (BMI) is a well-established etiological factor of cardiovascular disease [1]. Some studies have shown that measures of abdominal obesity, principally, waist circumference (WC), waist-to-hip ratio (WHR), and more recently, waist-to-height ratio (WHtR), are better correlated with cardiovascular disease morbidity and mortality than BMI [2-4]. Several studies have examined the association between waist- to -height ratio and diabetes mellitus, high fasting plasma glucose, dyslipidemia and metabolic syndrome [5-7]. Despite a growing burden of obesity and hypertension in developing countries, there is limited information on the contribution of body mass index (BMI) and waist-to-height ratio to blood pressure in these populations. The relationship between waist-to-height ratio and BP has long been the subject of epidemiological research. Positive associations between body mass and BP have been documented in Caucasian populations [8].This relationship, however, is not sufficiently explored among lean populations in India. Heart rate recovery is an independent risk factor for cardiovascular disease and mortality [9, 10]. Heart rate recovery is mainly thought to be a function of vagal reactivation, with a delayed decrease in heart rate recovery reflecting a reduction in vagal tone [11]. Abnormal heart rate recovery after exercise is therefore considered to be a measure of autonomic dysfunction [12]. Cardiac parasympathetic activity (vagal tone) increases with weight loss [13, 14]. The burden of cardiovascular risk associated with obesity disproportionately affects African Americans and little is known about ethnic/racial differences in the relationship of obesity to cardiometabolic risk [15]. Hence this study was design to evaluate the influence of body mass index and waist to height ratio which are known predictors of cardiovascular diseases, with % recovery heart rate in male adult subjects of Bijapur, Karnataka, India.
2. Materials and Methods
Adult males (n=52) belonging to mean age group of 24.16 + 8.12 were selected as subjects from the general population of north Karnataka, randomly for this study. The entire protocol was explained to all the subjects and written consent was obtained from volunteers. The experimental protocol was approved by Institutional Ethical Committee as per the ICMR guidelines 2006 on human subjects [16]. No prior history of cardiovascular, respiratory disease, musculoskeletal lesions was considered before inclusion of all the subjects in this study. All the selected subjects were non-smokers, non-alcoholics, non-diabetics and they were not under any medications which could affect their sub maximal aerobic fitness. Body weight was measured to the nearest 0.1 kg while the subjects were dressed in light clothing, height was measured to the nearest 0.1 cm and BMI was calculated on the basis of these measurements. Waist circumference was measured at the umbilical level, with subjects standing and breathing normally during the physical examination [17], after which W/Ht and WHR were calculated. All the subjects were asked to take rest in recumbent position for half an hour. The exercise tests were carried out in a well-ventilated room, using cycle ergometer (AFTON-ST-2488R). They were also properly instructed on how to perform the exercise test with prior demonstrations. Pre-exercise heart rate (HR) was measured before exercise by ECG. The testing protocol was comprised of an initial two-minute warm up exercise at a work load of 20 Watts, followed by a linear increase in workload every minute until the subject reached a targeted 70% of age–predicted maximum HR. The age–predicted maximum HR (HRmax) was determined as [HRmax = 208 minus (0.7 x age) [18]. The peak exercise HR was the highest value achieved at the termination of exercise test, after the subject has reached his predetermined HR. The post exercise HR rate was obtained 2 minutes after cessation of exercise. Electrocardiogram (ECG) was monitored by Ambulatory ECG Recorder (CARDIART-6108 BPL Electronic Company, Limited). Relative decrease of heart rate immediately after exercise was calculated as a percentage of peak HR: (peak HR–post HR) / peak HR x 100. Pre-exercise blood pressure (SBP and DBP) were measured when sitting on the cycle ergometer without pedaling by electronic blood pressure meter (EW 280W Japan). The peak exercise SBP and DBP were recorded immediately after exercise and post-exercise blood pressure were recorded 2 minutes after the cessation of exercise by using the following equation: (peak BP – post BP) / peak BP x100, [19-21]. All the values are expressed as mean + SD and range values. The relationships between the various variables were calculated using Pearson’s correlation coefficients,
3. Results & Discussion
The mean + SD and range values of anthropometric and physiological parameters of all the subjects are shown Table 1 and Table 2 respectively. Various anthropometric indices of obesity have been suggested to predict cardiovascular diseases. According to the classification of obesity BMI reflects overall obesity whereas waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) indicate abdominal and visceral adiposity [22]. There was a statistically significant positive correlation between BMI, waist hip ratio, waist to height ratio with mean arterial pressure (Table 3). Increase in body weight produces an increment in total blood volume and cardiac output that is caused in part by the increased metabolic demand induced by excess body weight. The increase in blood volume in turn increases venous return to the heart, increasing filling pressures in the ventricles and wall tension [23]. Increased body weight is also linked with increase in peripheral vascular resistance: endothelial dysfunction, insulin resistance, increased sympathetic activity and serum angiotensin II levels [24]. Though WHR is not significantly correlated with percent recovery heart rate, it is strongly correlated with WHtR. In this study a significant negative correlation was found between BMI and waist to height ratio with percent recovery heart rate (Table 3). Less waist circumference with normal average height and its ratio may have greater endurance as indicated by greater percent recovery heart rate as compared to greater waist circumference with greater height because proportion of the body must be taken into an account while considering cardiovascular fitness. As greater waist circumference alters body proportion, hence it makes an impact on percent recovery heart rate. Recovery of the heart rate immediately after exercise is a function of vagal reactivation [8]. Weight loss also improves autonomic function [25]. Lifestyle modification includes changes in diet and physical activity, increases in parasympathetic and decreases in sympathetic nerve activity, and improved HR recovery have been seen after weight loss achieved by dieting in obese individuals [11, 25]. In the present study there is significant negative corelation between mean arterial pressure and percent recovery heart rate. Heart rate recovery after submaximal reflects autonomic activity. Decrease heart rate recovery may be due to a defect in sympathetic withdrawal, vagal reactivation, or both. When sympathetic activity is amplified, the increased cardiovascular workload and hemodynamic stress result in endothelial dysfunction, coronary artery spasm, left ventricular hypertrophy, arrhythmias, stroke, and increased cardiac mortality. However, increased parasympathetic activity is protective against ischemia related dysrhythmias, and also reduces heart rate and blood pressure [27, 28]. An abnormal heart rate recovery response may be due to autonomic dysfunction and that the mechanism of increased mortality associated with this finding might be more related to autonomic dysfunction [29]. Hence to evaluate the cardiovascular fitness and also to screen metabolic syndrome, WHR ratio is routinely used by clinicians in tropical countries, but in our study WHtR was found to be a better predictor of cardiovascular fitness (% recovery heart rate) than WHR. Hence a correlation between WHtR and % recovery heart rate may also be used to interpret various cardiovascular problems linked to insulin resistance or metabolic syndrome.
4. Conclusion:
Our study concludes that WHt.R may be considered as an important anthropometrical tool which correlates with cardiovascular fitness among young male adults of Bijapur. This anthropometrical parameter may also be used to evaluate metabolic syndrome or insulin resistance diabetic status of an individual.
Conflict of interest statement
We declare that we have no conflict of interest.
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