|Year : 2017 | Volume
| Issue : 2 | Page : 62-65
Correlation of waist circumference and waist-to-height ratio with maximal aerobic capacity in young adults
Himel Mondal, Snigdha Prava Mishra
Department of Physiology, MKCG Medical College, Ganjam, Odisha, India
|Date of Submission||05-Jan-2017|
|Date of Acceptance||30-Jan-2017|
|Date of Web Publication||15-Jun-2017|
Department of Physiology, MKCG Medical College, Ganjam - 760 004, Odisha
Source of Support: None, Conflict of Interest: None
Background: Central obesity or abdominal obesity doubles the risk of cardiovascular disease when compared to gynoid pattern of fat distribution. Maximal oxygen consumption (V.O2max) is an index of aerobic capacity and low level of V.O2maxis an established risk factor for cardiovascular diseases. Aim: This study aimed to evaluate the effect of central obesity on V.O2maxin young adults. Materials and Methods: A cross-sectional study with 133 apparently healthy subjects (male = 83, female = 50) in the age group of 17–25 years was carried out. Waist circumference (WC) was measured by fiberglass measuring tape to nearest 0.1 cm. V.O2maxwas measured by submaximal treadmill exercise test by first two stages of Bruce protocol. Data were analyzed using unpaired t-test and Pearson correlation according to necessity.
Results: Male subjects (n = 83) had statistically significant (P < 0.0001) higher V.O2max(mean ± standard deviation) (38.024 ± 6.243) than the female subjects (n = 50) (33.611 ± 3.470). WC showed negative correlation with V.O2max(r = −0.629, P < 0.0001). Waist-to-height ratio (WHtR) showed more negative correlation (r = −0.728, P < 0.0001) with V.O2max. Conclusions: Male has more aerobic capacity than female. Increase in WC and WHtR are associated with decreases in V.O2max. When compared to WC, WHtR is better predictor variable for V.O2max.
Keywords: Abdominal fat, cardiorespiratory fitness, central obesity, maximal oxygen consumption, waist-to-stature ratio
|How to cite this article:|
Mondal H, Mishra SP. Correlation of waist circumference and waist-to-height ratio with maximal aerobic capacity in young adults. J Health Res Rev 2017;4:62-5
|How to cite this URL:|
Mondal H, Mishra SP. Correlation of waist circumference and waist-to-height ratio with maximal aerobic capacity in young adults. J Health Res Rev [serial online] 2017 [cited 2017 Jun 22];4:62-5. Available from: http://www.jhrr.org/text.asp?2017/4/2/62/208119
| Introduction|| |
Risk of cardiovascular diseases increases with increasing degree of obesity. Weight gain in the abdominal area or central obesity doubles the risk of obesity-related health problems when compared with gynoid pattern of fat distribution. Waist circumference (WC) alone has been shown to correlate more strongly to direct measures of abdominal fat accumulation.,, Waist-to-height ratio (WHtR) is another simple anthropometric parameter which showed better association with cardiovascular health risks when compared to WC., For a given height, WHtR reflects the amount of fat stored in upper portion of body.
Maximal oxygen consumption (V.O2max) is an index of aerobic capacity and it is the best measure of fitness for continuous exercise. It is used diversely in clinical science as an indicator of population-based cardiorespiratory fitness. A low level of V.O2max has been established as an independent risk factor for cardiovascular diseases. With this background, we carried out this study to find any correlation between central obesity parameters and maximal aerobic capacity.
| Materials And Methods|| |
After designing the study protocol, clearance from Institutional Ethics Committee was obtained. The study was carried out in the postgraduate research laboratory of Department of Physiology, MKCG Medical College, Ganjam, Odisha from October 2015 to December 2016.
Sample size calculation: We reviewed similar research work and found the study by Dagan et al. to take as a reference. They found a correlation of WC and V.O2max for male as r = −0.377 and female as r = −0.49. We assumed that we would get correlation coefficient like their study. So with a = 0.05 and power of the study as 90%, we calculated the minimum sample size for the study. Estimated minimum sample size was male = 73 and female = 40 (total = 113). With consideration of chance of high dropout rate, we multiplied the minimum sample size with 1.25 and included 142 first year medical students of 17–25 age group as a convenience sample. The aim of this study was described verbally and only volunteer students were included in the study after written consent. Students with any acute or chronic diseases, deformities, on any medication or addiction were excluded from the study. The final number of subjects completed both anthropometric measurements and submaximal exercise test was 133 (male = 83, female 50).
Weight was measured by digital weighing scale to nearest 0.1 kg. Height was measured by stadiometer to nearest 0.1 cm. Body mass index (BMI) was calculated according to Quetelet's equation. WC and hip circumference were measured with stretch resistant fiberglass measuring tape according to the guidelines by the World Health Organization. Measurements were taken in erect posture with hands by sides and feet positioned closed together. WC measurements were taken between 9 a.m. and 10 a.m. with students in fasting overnight. WC of male students was taken without upper body clothing and female with light clothing in front of female attendant. At the end of a normal respiration, the measurements were taken at the approximate midpoint between lower palpable rib and upper border of iliac crest with a measuring tape placed horizontal to the floor. Two measurements were taken and the average was taken as final measurement whereas the difference in two measurements was not >1 cm.
Test to determine maximal oxygen consumption
We used submaximal treadmill exercise test with first two stages of Bruce protocol. Before the exercise test, subjects were familiarized with the instruments and a trial of test was performed. Computerized treadmill (RMS, Vega 201 Stress Test System) program was set according to the first two stages of the Bruce treadmill protocol (1.7 mph at 10% Grade for 3 min and 2.5 mph at 12% Grade for 3 min) with a warm up stage of 2 min at gravitational level. Subjects walked on the treadmill for the stages, and steady state heart rate (HR) for each stage was obtained by Claritymed Cardiac Monitor. V.O2max was calculated from the age, HR of first and second stage of exercise, speed, and grade of the treadmill data by a Spreadsheet calculator made according to the formula by the American College of Sports Medicine health-related physical fitness assessment manual as shown in [Figure 1].
|Figure 1: Maximal oxygen consumption calculator in Spreadsheet software – Microsoft Excel® 2010|
Click here to view
Anthropometric parameters and V.O2max of male and female were expressed in mean and standard deviation (SD) and compared statistically by unpaired t-test with 95% confidence interval. Correlation between V.O2max and anthropometric parameters was obtained by Pearson correlation coefficient (r) with 95% confidence interval. Two-tailed P < 0.05 was considered statistically significant. Statistical analyses were carried out in Microsoft Excel ® 2010 and GraphPad Prism 6.01 (GraphPad Software, Inc., CA, USA) for windows software.
| Results|| |
The mean age of participants was 19.406 ± 1.101 (male = 19.578 ± 1.159, female = 19.120 ± 0.939) years. V.O2max(in ml/kg/min) in male subjects (n = 83) was higher (mean ± SD) (38.024 ± 6.243) than the female (n = 50) subjects (33.611 ± 3.470) and the difference was statistically significant (P < 0.0001). WC of male (75.558 ± 9.639) was higher than female (73.638 ± 7.134) but the difference was not statistically significant (P = 0.224). The difference of WHtR of male (0.449 ± 0.059) and female (0.467 ± 0.049) was not significant (P = 0.081). The anthropometric parameters of male and female and respective P value of unpaired t-test are shown in [Table 1]. When we carried out Pearson's correlation, V.O2max showed a negative correlation with WC (r = −0.629, P < 0.0001). The correlation coefficient of V.O2max and WC for male was r = −0.745, P < 0.0001, and female was r = −0.663, P < 0.0001. Correlation coefficient of V.O2max and WHtR (r = −0.728, P < 0.0001) showed stronger negative correlation compared to WC quantitatively. The correlation coefficient of V.O2max and WHtR for male was r = −0.749, P < 0.0001 and female was r = −0.711, P < 0.0001. Correlation of V.O2max and anthropometric parameters are shown in [Table 2]. Linear regression of V.O2max with WC is shown in [Figure 2] and V.O2max with WHtR is shown in [Figure 3].
|Table 2: Correlation of maximal oxygen consumption with body mass index, waist circumference, waist-to-height ratio and waist-to-hip ratio|
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|Figure 2: Linear regression scatterplot of maximal oxygen consumption (ml/kg/min) and waist circumference (cm) with trend line (R2 = 0.3955; P < 0.0001; Equation: Y = -0.9595*X + 109.7)|
Click here to view
|Figure 3: Linear regression scatterplot of maximal oxygen consumption (ml/kg/min) and waist-to-height ratio with trend line (R2 = 0.5295; P < 0.0001; Equation: Y = –0.007129*X +0.7152)|
Click here to view
| Discussion|| |
Abdominal fat is more easily mobilized into the bloodstream and increases risk of cardiovascular diseases. Men tend to gain more fat in the abdominal area whereas women tend to store more fat in buttocks and thigh. However, any person with central obesity carries increased health risks. In this study, male (75.558 ± 9.639) had more WC than female (73.638 ± 7.134), but statistically insignificant difference in WC predisposes both male and female equally for central obesity-related health risks. Finding of statistically significant increased WHR in male subjects supports the gynoid pattern of fat distribution in female.
Maximal aerobic capacity in male subjects was 38.024 ± 6.243 ml/kg/min, and female subjects were 33.611 ± 3.470 ml/kg/min, and both of the levels was in poor category according to the Cooper Institute centile values. The result of this study showed that male has more aerobic capacity than female and this gender difference is concordant with the finding of Zebrowska et al., Sharma et al., and Loe et al.
WC showed a negative correlation with V.O2max(r = −0.629, P < 0.0001). Hence increase in WC may predispose to decreased aerobic capacity. Negative correlation of aerobic capacity and WC was also reported by Dagan et al. Hence, WC can be used as a tool for an assumption about the aerobic capacity of healthy young adult person. Male showed more strong negative correlation between V.O2max and WC (r = −0.745, P < 0.0001) than female (r = −0.663, P < 0.0001). So, increased central obesity in males may be considered more disadvantageous for aerobic capacity than female.
It is established that WHtR is a simpler and more predictive indicator of central obesity-related health risks and it is better than BMI and WC for measuring adiposity in adolescents., WHtR was more negatively (r = −0.728, P < 0.0001) correlated with V.O2max than WC. The difference between the correlation coefficient between male (r = −0.749, P < 0.0001) and female (r = −0.711, P < 0.0001) was not so distinct as found with WC. Hence, WHtR can be considered as a better parameter for early detection of lower V.O2max irrespective of sex.
BMI (r = −0.352, P < 0.0001) and WHR (r = −0.206, P = 0.018) also showed negative correlation with V.O2max but the correlation coefficients do not indicate a strong negative correlation. BMI does not differentiate between the body fat and muscle mass; rather, it uses whole body weight. Hence, this may be underlying reason for a weak correlation when compared to WC and WHtR which are more accepted parameters to measure body fat indirectly. Study by Joshi et al. found a significant effect of BMI on aerobic fitness, but in contrast, Nikolaïdis found insignificant correlation between BMI and aerobic fitness level. This diverse result may be due to difference in physical activity level of individual subject, ratio of Type I and Type II muscle fiber, different methods used to quantify maximal aerobic capacity and different age group of subjects.
This study was carried out on a convenience sample from medical students who lead a sedentary lifestyle. The lack of regular physical exercise increases the risk of body fat accumulation. The relative amount of muscle mass also decreases due to increased body fat burden on total body weight. This may be contributing factor for low cardiorespiratory fitness in sedentary young adults. Theoretically, maximal aerobic capacity depends on the cardiovascular and pulmonary system which helps to carry oxygen from the environment to exercising muscle. It is well documented that pulmonary ventilation can be increased even after the maximum cardiac output has been reached. Cardiac output can also be increased to such a level that is surplus than the ability of the muscles to receive it. In this study, subjects with any cardiovascular or pulmonary diseases were excluded, so it was assumed that the cardiovascular and pulmonary system were optimum in their activity. Hence, the contribution of exercising muscle was ample for V.O2max of individual. Increase in body fat increases the load the worker when compared to individual with less body fat. This is the underlying reason why endurance contestants reduce body fat content to a minimum level. Central obesity not only increase the total body fat contents, it also contributes to increase obesity related morbidity., From this study, it is evident that increase in central obesity is an indicator of low level of aerobic capacity in young adults.
We measured the central obesity indirectly. Direct measure of abdominal fat and V.O2max measurement by maximal exercise test with simultaneous gas analysis would reflect more accurate result. Further studies with large sample size of different age groups may provide more information about the relation of central obesity and V.O2max in general population.
| Conclusions|| |
Male has more aerobic capacity in comparison to female. Central obesity measured by WC and WHtR has a negative effect on maximal aerobic capacity. WHtR may be considered better predictor variable than BMI, WC, and WHR for maximal aerobic capacity.
We would like to thank Dr. Debasish Das, Senior Resident, Department of Physiology, MKCG Medical College for his substantial help during this research work. We acknowledge the active participation of 1st year medical students of 2015–2016 and 2016–2017 batches.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]