The role of anthropometrics in predicting the maximum oxygen consumption in emergency medicine students

1 Introduction

Fitness of job with individuals’ capabilities and limitations is one of the important issues in Ergonomics. Each type of work requires a certain amount of energy. On the other hand, each human has a certain amount of energy for work based on the cardiovascular and physical capacity. Therefore, the fitness between these two features (required energy for work and capacity of energy production) is essential in order to increase effectiveness and efficiency in the working systems [1].

People who work in emergency medicine are exposed to many risks, which can affect adversely on their health and casualties. Emergency medicine personnel provide pre-hospital care and deal with complicated and vulnerable cases [2, 3]. Given the unique nature of the job, emergency medicine staff are more likely to suffer from psychological disorders than the general population [4]. According to previous studies, various factors can result in tension in the Emergency Medical Service (EMS) healthy staff including care-related tension, inappropriate rest time, lack of equipment, lack of tools for evaluation of job pattern, lack of personnel, exposure to pollutants, and type of job [5]. It is important to select people based on physical and psychological abilities [6, 7].

The maximum oxygen consumption is defined as the maximum capability of oxygen delivery and consumption during physical activity. It is calculated in terms of millimeter oxygen per kilogram of body weight per minute [8–10]. High level of this figure can lead to higher capacity for work and endurance and lower level of fatigue [7, 11].

Anthropometry including body structure, dimensions and compositions is one of the factors contributing to the maximum oxygen consumption [12]. People have various anthropometrics dimensions and body size; consequently, maximum oxygen consumption is different. For example, people with a wider chest hold much more volume of oxygen in the lungs, and more oxygen is provided to the muscle fibers and other cells. Thus, availability of more oxygen to the muscle cells increases the rate of aerobic metabolism and reduces glycolytic metabolism and production of lactate and consequently fatigue [13–15]. Oxygenation to the cells also depends on optimal function of oxygen transfer (function of the cardiovascular system) and health [16, 17].

Body composition is measured by percentage of body fat. Many studies have shown a strong relationship between anthropometrics characteristics and body composition with exercise [14, 18]. Results of other studies indicate that percentage of the body fat had a significant negative relationship with aerobic capacity [18, 19]. Many studies have also shown that high percentage of the body fat not only increases weight but also decreases oxygen in the muscles; consequently, it results in decrease of the cardiorespiratory endurance [18, 20]. This study aimed to predict the maximum oxygen consumption based on anthropometrics in the emergency medicine students.

2 Methods

This cross-sectional study was conducted on the total male emergency medicine students (n = 56) at Qazvin University of Medical Sciences in 2018. In Iran, only men are employed for emergency medical service. Exclusion criteria were history of cardiovascular, respiratory, and musculoskeletal diseases, taking analgesic medications and job with a high level of physical activity.

After explaining the study to the participants, they completed the consent form and Physical Activity Readiness Questionnaire (PAR-Q) [21]. According to this questionnaire, the risk of cardiovascular diseases during exercise is classified into three levels of low, moderate, and high. If a participant reported one of the signs and symptoms of cardiovascular diseases, he was considered in the high-risk level and was excluded from the study [22]. In order to provide equal condition in measurement, investigators used equipment of ergonomic lab in all measurement. Then, people with light cloth performed Gerkin treadmill test to measure the maximum oxygen consumption and anthropometrics (dimensions and compositions).

3 Results

The mean age of participants was 21.69 years. Other demographic characteristics are presented in Table 2.

The mean and standard deviation of maximum oxygen consumption by Gerkin treadmill test was 4.17±0.39 in the emergency medicine students. The mean and standard deviation of the abdomen circumference was 87.42±9.34. The mean and standard deviation of other anthropometric characteristics are presented in Table 3.

There was a significant positive association between the maximum oxygen consumption and anthropometric dimensions (Table 4).

According to the results of this study, the body fat, the waist-to-hip ratio and the body mass index had a significant relationship with the maximum oxygen consumption (Table 5).

According to Table 6, adjusted ratio R² was 0.721, which indicates 72.1% of change in the maximum oxygen consumption in the emergency medicine students is dependent to leg length, body fat and BMI. In other words, independent variables predict two-third variance in maximum oxygen consumption.

Of the anthropometric dimensions, leg length has the most effect in predicting maximum oxygen consumption. As effect of the waist to buttocks was non-significant in relation to other variables predicting maximum oxygen consumption, it was not used in the equation.

Linear equation of estimating Maximum oxygen consumption was calculated based on constant of regression and coefficients of independent variables as the following:

Maximum oxygen consumption = - 1 . 9 0 - ( 0 . 27 × percentage of body fat ) + ( 0 . 49 × leg length ) + ( 0 . 79 × BMI )(1)

Humans are different in terms of physical and spiritual aspects, anthropometrics, and consequently oxygen consumption [29, 30]. The results of this study indicate that the mean of maximum oxygen consumption is 4.17 l/min, which is consistent with studies conducted by Rafieepour et al. on students (38.2 ml/Kg.min) in Hamedan [29], Tierny et al. on firefighters (4.85 lit/min) [24] and Vandersmissen et al (37.3 ml/Kg.min) [31]. Condition of the study setting affects maximum oxygen consumption; therefore, lack of control of these conditions can contribute to differences in figure in different studies. In addition, people with different descents have varying BMI and body structure and composition. Age and life style could explain difference in estimating maximum oxygen consumption in research on different societies.

In this study, the means of anthropometrics depth, width and height of the chest are contradicted with the mean of these three dimensions in a study conducted by Rafieepour et al. [29] and mean waist circumference in the study by Ali Nejad et al. [32]. This difference could be explained by different age range of participants and gender differences in the waist circumference.

This study showed a significant relationship between all anthropometric dimensions and maximum oxygen consumption, which is consistent with results of the study conducted by Rafieepour et al. on 160 students and anthropometrics dimensions of depth, height and width of the chest effect on maximum oxygen consumption [29]. Big chest and cardiovascular and respiratory systems result in absorbing more oxygen in the lungs and transferring to the muscles cells. Wientzek et al. reported a significant relationship between anthropometrics dimensions and maximum oxygen consumption [33]. Furthermore, the results of this study are consistent with the study conducted by Sekeljik et al. [34], which showed a significant relationship between anthropometrics dimensions and maximum oxygen consumption. The increase of anthropometrics dimensions result in increasing the oxygen consumption in the dependent extremities and improvement of cardio-respiratory status. Since the leg length affects distance of walking, it could increase oxygen consumption [35].

One of the finding of this study is significant relationships between maximum oxygen consumption with fat percentage, waist to hip ratio, and BMI, which is consistent with studies conducted by Mondal et al. [18], Wientzek et al. [33], Sharma et al. [36], Ranson et al. [37], Goran et al. [38]. Increased body fat leads to lower waist-to-hip ratio and body mass index, which reduces cardiopulmonary function and ultimately reduces oxygen consumption [18].

One of the limitations of this study is small number of emergency medicine students at Qazvin University of Medical Sciences, limited anthropometrics parameters, and lack of equipment for indirect measurement of oxygen. In this study, Gerkin treadmill test was used, which is one of the sub-optimal indirect tests. Therefore, future studies should be conducted using optimal direct and indirect tests and further anthropometrics parameters in order to obtain more accurate results.

5 Conclusion

The results of this study indicate that anthropometrics is one of the contributing factors to maximum oxygen consumption, which can affect providing required energy for activities for daily living and capabilities in various jobs, particularly emergency medicine. Therefore, it is necessary to consider body dimensions and compositions to select students and match their capabilities with required energy for the job.