Table of Contents  

Davison, Fawad, Nevill, Boreham, McClean, and Petherbridge: Effects of physical activity in an overweight Emirati school-based male population – a preliminary investigation

Introduction

A strong body of evidence, comprising both observational and experimental research, indicates that regular participation in physical activity among young people can provide immediate and long-term benefits for both physical and psychological well-being. The benefits of regular physical activity are widely documented; for example, in adults, engaging in 30 minutes of moderate-intensity physical activity at least 5 days a week can prevent and manage over 20 chronic conditions, including coronary heart disease, stroke, type 2 diabetes mellitus, cancer, obesity, mental health problems and musculoskeletal conditions.1 Physical inactivity, in contrast, is the fourth leading risk factor for global mortality, accounting for 6% of deaths globally and ranking before being overweight and obese (5%) and after high blood pressure (BP) (13%), tobacco use (9%) and high blood glucose levels (6%).1

The Gulf Co-operation Council countries, including the United Arab Emirates (UAE), have witnessed significant lifestyle changes due to rapid urbanization, dominance of the automobile for personal travel, availability of high-fat and high-calorie foods, increased reliance on computer and telecommunication technology as well as reduced occupational work demands.2 These lifestyle changes have had a considerable impact on reducing the physical requirements of daily life and have encouraged sedentary lifestyles among both young people and adults. Consequently, these remarkable lifestyle transformations are thought to be largely responsible for the epidemic of non-communicable diseases in the Arab region.3,4 A study by Al-Sarraj et al.5 in 2010 reported that approximately 41% of the UAE population were suffering from metabolic syndromes, predisposing this population to an increased risk of developing diabetes and cardiovascular disease. It has recently been reported that only 7% of Emiratis in the age group 40–59 years are achieving the correct level of exercise to remain healthy,6 and it is estimated that only 14% of the UAE population engage in physical activity. This statistic contributes towards the 19.2% of the population currently suffering from diabetes mellitus, placing the UAE amongst the highest prevalence of diabetes mellitus worldwide.7

The rise in childhood and adolescent obesity has been deemed as one of the most serious public health issues facing society today.8 It has been highlighted that cardiovascular disease originates in childhood, yet it may not become evident until adulthood.9 Although childhood obesity has been observed and widely reported in developed countries in recent years, there is an ever-increasing prevalence in developing countries. This prevalence of childhood obesity is high in the Middle East and central and eastern Europe.10 Studies of physical activity interventions in obese Emirati populations are to date non-existent. Moreover, it has been recently stated that there is an urgent need for public health involvement and well-controlled studies that take into consideration exercise intervention programmes among Emirati citizens.5

Integrating a physical activity interventional programme into a school-based environment offers a novel approach to increasing physical activity throughout the day, coupled with the potential to reduce some of major risk factors associated with chronic disease, such as type 2 diabetes mellitus. Thus, the major aim of this study is to explore the effects of a chronic physical activity intervention and risk factors associated with disease in an overweight Emirati school-based population. It is envisaged that the findings from this regional study will provide data on the importance of physical activity in order to reduce susceptibility to disease in an overweight Emirati population. This study will also provide essential data for developing additional intervention strategies for preventing and controlling non-communicable diseases.

Methodology

Participants

A total of 23 (n = 23) overweight school-based male individuals (mean ± standard deviation: age 14 ± 3 years, stature 157 ± 17 cm, body weight 69 ± 26 kg, body mass index (BMI) 28 ± 6 kg/m2 and VO2peak 33 ± 7 ml/kg/min), living in the region of Dubai, UAE, volunteered to take part in this study following institutional ethics approval and written informed consent. Participants included were male, native Emiratis and had a BMI > 25%; those participants reporting cardiovascular-related problems, suffering from illness or infection, or with a muscle or bone injury were excluded.

Participant recruitment

Recruitment of children was carried out in collaboration with the staff at the American International School in Dubai. Parents of children in Grades 5–8 (age 14 years ± 3 years) were contacted by letter and informed of the study. The letter was followed up by a series of phone calls and emails to ascertain willingness for their child's participation. Participant information sheets were distributed to each family household and subsequent written informed consent from both parent and child was obtained prior to study participation. All documentation was made available in English and translated into Arabic by a representative of the American International School in Dubai. Participation was voluntary with the opportunity to drop out at any time without explanation.

Study design

Following recruitment, medical history questionnaires were distributed and each child was required to participate in a structured 12-week physical activity school-based intervention programme. Both prior to and following the 12-week intervention programme, each participant completed a series of physiological and biochemical test profiles.

Physical activity intervention programme

The intervention programme consisted of 60 minutes a day, over 5 days a week, of physical activity and was implemented over 12 weeks. The 60 minutes did not include time for changing clothes prior to or after physical activity. Five minutes were used providing explanations, organizing the children and other low-intensity activities. For the remaining 55 minutes, a physical education teacher carried out moderate- to vigorous-intensity physical activity, resulting in the children sweating and being out of breath. The vigorous physical activity component was accomplished by selecting a variety of activities such as running, relay racing, obstacles courses and various forms of high-intensity active play. These activities were interspersed and routinely performed alongside game sports such as football and basketball. Each lesson was planned so the activities were varied, enjoyable, exciting and pleasurable. All activities were non-competitive and adherence was excellent (100% over the 12-week period).

Physiological and biochemical measurements

All measurements were carried out in accordance to ethical approval and taken by the school doctor and physiologist at each time point (pre and post intervention) over the course of the 12 weeks.

Body mass index

Body weight was measured to the nearest 100 g using Seca weight scales (Seca Ltd, Hamburg, Germany). Participants were weighed barefooted and without excess outer clothing. Height was measured to the nearest 0.5 cm using a Seca portable height measure (Seca Ltd, Hamburg, Germany). BMI was calculated using the formula weight (kg)/height (m2) and was classified according to the International Obesity Task Force criteria.11

Blood pressure

Diastolic and systolic BP was measured using an Omron M5-1 fully automated BP monitor (Omron, Surrey, UK). BP was measured on the upper right arm using an appropriate child-sized cuff.

Arterial stiffness

A Pulse Trace PCA2 (Micro Medical, Basingstoke, UK) device was utilized to measure arterial stiffness. The Pulse Trace PCA2 estimates large-artery stiffness from the pulse waveform obtained in the finger (digital volume pulse) with an infrared sensor (photo-plethysmography) from the index finger of the right hand. The procedure requires a probe to be placed on the index finger while a measurement of time is recorded for the pulse waves to travel through the arterial system, thus, providing a simple but accurate way of measuring arterial stiffness.12

Predicted cardiovascular fitness

A predication of cardiorespiratory fitness was confirmed using the standardized bleep running test until volitional exhaustion.13 This test involved each child running for approximately 7–10 minutes. This test is regarded as progressive and incremental; therefore, as exercise duration increased, so did exercise intensity, until the subject decided to stop exercising. Aerobic fitness is defined as peak oxygen intake (VO2peak).

Blood sampling

All blood sampling was carried out in a sterile room that was appropriate for the withdrawal of blood in accordance with normal blood sample extraction regulation and procedures. Venous blood samples were collected between 8 and 10 am, following a 10-hour standardized overnight fast. The blood was analysed for total levels of cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides and glucose.

Blood biochemistry analysis

Total cholesterol, triglycerides and HDL cholesterol were ascertained using enzyme assay kits, using the Aeroset™ analyser (Abbott Laboratories, Illinois, IL, USA). Estimates of LDL cholesterol were calculated using the Friedewald formula.14 Plasma glucose concentration was ascertained by an immobilized enzyme membrane method in conjunction with a Clarke electrode on an YSI 2300 analyser (YSI Life Sciences, Yellow Springs, OH, USA). The coefficient of variation for total cholesterol, HDL, triglycerides and glucose was 0.7%, 3%, 2.3% and 0.9%, respectively.

Strength endurance

Strength endurance was measured using the 30-second press-up and sit-up motion (using counts) until volitional exhaustion and failure. Elastic leg strength was ascertained using a standing board jump test.15

Statistical techniques and analysis

Prospective subject number was calculated using Minitab (Minitab Ltd, Coventry, UK). Assuming a standard deviation of a difference of 4.5 ml/kg/min (obtained from the peak VO2 delta standard error of the mean of 0.4 in Resaland et al.16), a sample size of > 20 was required to detect an increase of 3.5 ml/kg/min (7%) in cardiovascular fitness (80% power and alpha = 0.05) from pre to post intervention.

Statistical analysis

All statistical analyses were performed using SPSS version 20 (SPSS Inc. Chicago, IL, USA). Normal data distribution was confirmed using a Shapiro–Wilks test. Parametric independent-sample t-tests were used to ascertain the difference between pre and post intervention time points and a confidence interval of 95% confirmed statistical significance (P < 0.05) between pre and post intervention data. All data were expressed as mean ± standard deviation.

Results

Physiological and fitness parameters

Table 1 demonstrates the data prior to, and immediately following, the exercise training programme. Although systolic and diastolic BP scores are clinically normal (i.e.120/80 mmHg), the resting arterial stiffness is slightly raised over normal values. There was a significant change in body weight and fitness as a function of exercise (Table 1 and Figure 1). The difference between the baseline and the post intervention was statistically significant at P < 0.05.

TABLE 1

Physiological and fitness indices at baseline and following 12 weeks of physical activity (n = 23)

Variable Baseline Post intervention
Body weight (kg) 69 ± 19 56 ±18a
Arterial stiffness 6.3 ± 0.7 6.0 ± 0.9
Systolic BP (mmHg) 110 ± 11 108 ± 14
Diastolic BP (mmHg) 70 ± 8 69 ± 10
Sit-ups (30 seconds) 20 ± 7 22 ± 6
Press ups (30 seconds) 16 ± 10 17 ± 7
Standing broad jump (feet) 5 ± 1 5 ± 1

a A difference between the baseline and post intervention.

FIGURE 1

Cardiorespiratory fitness at baseline and following 12 weeks of physical activity (n = 23). *A difference between baseline and post intervention.

6-3-13-fig1.jpg

Blood biochemistry

Table 2 shows the average blood concentration prior to, and following, exercise. Although all baseline average values were within a normal clinical reference range, a number of individual biochemical values were disturbing. For example, assuming normal clinical reference values (blood glucose > 100 mg/dl, total cholesterol > 200 mg/dl, HDL cholesterol < 40 mg/dl, LDL cholesterol > 130 mg/dl, triglycerides > 200 mg/dl), four subjects had a blood glucose concentration of > 105 mg/dl, three subjects had a total cholesterol concentration of > 200 mg/dl, two subjects had a triglycerides > 200 mg/dl, 10 subjects had a HDL of < 40 mg/dl and five subjects had a LDL concentration of ≥ 130 mg/dl (up to 168 mg/dl). Although most indices follow a trend for improvement post intervention, with the exception of HDL cholesterol (at a baseline of 44 ± 10 mg/dl vs. 44 ± 9 mg/dl post intervention, P > 0.05) the differences were not significant (P > 0.05 vs. baseline).

TABLE 2

Biochemical indices at baseline and following 12 weeks of physical activity (n = 23)

Variable Baseline Post intervention
Glucose (mg/dl) 93 ± 4 91 ± 5
Cholesterol (mg/dl) 160 ± 29 157 ± 27
Triglycerides (mg/dl) 90 ± 50 89 ± 31
LDL cholesterol (mg/dl) 101 ± 23 96 ± 23

There was no significant difference between baseline and post-intervention for any metabolite (P > 0.05).

DISCUSSION

The main finding of this study indicates that a structured 12-week exercise intervention in a random selection of overweight Emirati males can improve overall cardiorespiratory fitness and body composition. To our knowledge, this is the first UAE-based study to report that consistent exercise training per se can positively target diabetes risk in a school-based population. Although there was a trend for change in BMI, blood biochemical indices, arterial stiffness, blood pressure and strength, no statistical changes were observed from baseline to post intervention.

The improvement in cardiorespiratory fitness is consistent with published literature. For example, Resaland et al.17 observed a change in peak fitness in children from Norway following a 2-year school-based physical activity intervention. In addition, Baquet et al.18 suggests that exercise training in children and adolescents can improve cardiorespiratory fitness by as much as 6%. A plausible explanation for the change in fitness following exercise training in the current study could be related to a change in body mass observed in this overweight population. Another reason for the improvement observed in fitness may be due to adaptation at the basic muscle cellular level and/or significant cardiovascular structural changes. These structural changes would allow for a greater exercise output and performance.16

In contrast, a number of studies have observed no change in cardiorespiratory fitness following a pattern of physical activity. In Germany, children participated in a 4-year programme in which they completed one extra health education class per week, which lasted a total of 30 minutes, but no statistical change was found in the 6-minute running test.19 A similar finding was observed in the Copenhagen school child intervention study, in which twice-weekly physical activity was doubled to 90 minutes of exercise over 3 years and no change in fitness was found.20 Resaland et al.16 suggests that the volume and frequency of physical activity needs to be consistently high in order for cardiovascular improvement to occur. One of the strengths of our study is that the physical activity was performed for 60 minutes per day, at a moderate to high intensity, over 5 days a week. We claim that this rigorous approach may partially explain the positive changes in cardiovascular fitness observed in the present study.

Although body weight changed as a function of physical activity, there were no differences observed in BMI across the group. It is likely that the lack of change in BMI could be due to the small sample size. However, it is also possible that exercise training may have altered body composition. Carrel et al.21 reported a significantly greater loss of body weight despite no change to BMI in a randomized control trial involving school children. Moreover, it is known that for significant and long-term changes to be made to BMI, manipulation of diet is also paramount, and Resaland et al.16 claim that dietary modification in combination with physical activity can have a greater influence on body weight than exercise alone.

It is now accepted that a strong association exists between low cardiorespiratory fitness and mortality;22 however, our data support the notion that enhanced cardiovascular fitness can hypothetically reduce the risk of type 2 diabetes and cardiovascular disease in this school-based population.23 Generally, physical activity and improved fitness (or vice versa) is positively related to a healthier metabolic profile, e.g. there are beneficial changes to insulin resistance and glucose intolerance. The literature suggests that metabolic benefits can be enjoyed by young people, especially by those most at risk.23 Data from Raitakari et al.24 demonstrate that young male individuals consistently categorized as physically active had lower fasting insulin levels than their sedentary peers. In a comparison of 10-week physical activity programmes for obese African-American children up to 11 years old, there was a reduction in glycosylated haemoglobin and an improvement in the level of fasting glucose was observed.25

It is postulated that, because of low subject numbers, there was no overall statistical change in fasting biochemical indices following 12 weeks of exercise activity. However, there was a trend towards an improvement in fasting peripheral glucose, triglycerides and cholesterol, and further work with a much larger sample size is warranted to follow up on this observation. Moreover, as this was a heterogeneous group of overweight school children, it is important in this instance to examine the biochemical data from an individual perspective. In our cohort population, it was observed that a number of subjects had a baseline biochemical value above the clinical norm (raised blood glucose and lipids); thus, they are predisposed to an increased risk of type 2 diabetes mellitus and cardiovascular disease. Obesity is known to increase lipids within the peripheral circulation and increased exposure of the liver to fatty acids can increase hepatic glucose production and outputs of LDL cholesterol, which, in turn, results in glucose intolerance and hypertriglyceridaemia,26 and the latter is commonly associated with insulin resistance.27 Our individualized approach clearly highlights an increased risk of developing diabetes in a number of Emirati school-based students and immediate intervention is required to reduce the likelihood of contracting a metabolic-related disease later in life.

It is acknowledged that this study has several limitations, e.g. this was a preliminary investigation and only boys participated. There is an obvious lack of a control group, such as an aged-matched cohort of students not participating in the 12-week physical exercise programme. Although this approach would support the experimental data, the primary aim of this study was to confirm the changes from baseline to post intervention on cardiorespiratory and metabolic fitness and health in Emirati students. The methodological approach adopted allowed our hypothesis-driven work to be meaningful. It is advised that future experiments within this area of investigation should include a greater number of subjects and careful consideration should be given to the use of a non-exercising control group.

Conclusions

Physical activity and its relationship with changing body weight and fitness, as outlined in this study, demonstrates the potential value of a structured school-based exercise training programme to reduce the susceptibility of type 2 diabetes and cardiovascular disease in young Emirati males. However, based on selective pre intervention data (predominantly blood biochemistry data), there is clear evidence that Emirati school-based individuals are highly susceptibility to type 2 diabetes mellitus and other related clinical conditions, such as heart disease, later in life. If these baseline clinical values are left untreated, premature death is inevitable in this young Emirati population. For any biochemical statistical change to occur as a function of exercise within this UAE population, a larger sample size may be required along with an increase in the intervention period. In our opinion, this preliminary study is important with regard to enhancing awareness and emphasizing the value of increased physical activity in a UAE school-based setting. The present study is in agreement with Al-Sarraj et al.5 in that there is an urgent need for public health involvement and large-scale studies that take into consideration exercise and nutrition intervention programmes among Emirati citizens.

Future perspectives

This preliminary study provides a brief insight into the health and fitness of a UAE school-based population. It is recommend that all stakeholders involved in promoting sport and physical activity within the UAE utilize this research to make a positive impact on decreasing the susceptibility of weight-related diseases within the UAE.

It is imperative that public bodies within the UAE use the findings of this study to support large-scale studies to examine the role of physical activity in a plethora of populations, such as overweight adults, type 2 diabetic adults, type 2 diabetic children and other adult and children ‘at-risk’ groups.

This study contributes towards developing the evidence base for health and physical activity for a school population within the UAE; however, it is important that the development of a market segmentation profile be implemented so that effective strategies can be put in place to reach those who do not engage in sport or physical activity.

It is expected that the findings from this regional study will provide data for public health authorities and policy-makers in the UAE to develop additional intervention strategies for preventing and controlling non-communicable diseases in a school-based population.

There is an immediate need to assess parental attitudes to health, sport and exercise in the UAE. Furthermore, diet and exercise advice needs to be highlighted in overweight UAE nationals.

Acknowledgements

The authors are grateful to Dr Mohammed Bin Sulayem, Dubai, for sponsoring the research.

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