Physical Activity Program as a Fitness Tool for Workers Exposed to Electromagnetic Field

Electromagnetic field (EMF) exposure at low frequencies may cause some health problems. The present study was designed to test the effect of a comprehensive physical activity program on some fitness aspects of exposed workers with emphasis on cardio-autonomic control. A pre-test post-test experimental design was adopted. A representative sample of 30 workers exposed to low frequency EMF from Abou Qir electrical power station, Alexandria, were included in the study after fulfilling eligible criteria. Each one of the workers was subjected to a predesigned questionnaire including inquiries about sleep pattern subjective symptoms, and work and health satisfaction. Measurements of anthropometric indices, resting heart rate and blood pressure were done. Resting 12 lead ECG and R-R variability test during deep breathing were performed. A venous blood sample was taken for serum cholesterol and complete blood count determination. All these parameters were measured for the participants before and after implementation of a standardized physical activity program (PAP) for 12 weeks. Results revealed significant improvement of some subjective and general complaints, and work and health satisfaction (p<0.05 for all). Heart rate, systolic blood pressure and R-R variability indices showed significant favorable effect of the PAP in the direction of augmenting the protective parasympathetic tone. In conclusion, PAP for workers exposed to EMF seems to be a good tool to improve their fitness and to ameliorate some health risks, emphasizing its importance in preventive implications. INTRODUCTION Electromagnetic field (EMF) is determined by the force effect due to summation of electric and magnetic fields. It comprises a broad spectrum of non-ionizing radiation.(1,2) Extremely low frequency EMF is existing whenever electric wiring, electric 100 Bull High Inst Public Health Vol.39 No.1 [2009] motors and electric devices are found. Exposure may occur at home, at job and in electric vehicles. Workers in electric utilities and nearby power lines are at great risk.(1) the magnetic component of exposure is the suspicious part of low frequency EMF especially among electric utility workers.(3) On the other hand, high frequency EMF is another issue expressed as radiofrequency radiation which is present in many fields including mobile phones and their base stations.(4,5) Since the late part of the 20th century there is increasing interest in the health effects of low frequency EMF especially in the form of subjective complaints including neurasthenic symptoms and sleep troubles, disturbances in cardiovascular and gastrointestinal functions and transient hematologic changes.(6) There are also, some existing concerns about childhood leukemias and certain types of cancer.(7) Metabolic parameters including cholesterol may be adversely affected due to exposure to low frequency EMF.(8) Cardiovascular diseases among electric utility workers were studied.(3,9-11) Indices of magnetic field exposure were consistently related to mortality from arrhythmia.(3,11) Heart rate and heart rate variability may be affected by this exposure in a pattern suggesting the domination of sympathetic activity and imposing further cardiovascular risk.(12,13) Most of the reported health findings due to exposure to low frequency EMF seems to be related to workers' fitness and autonomic nervous control.(6) According to the latest guidelines,(14) all healthy adults aged 18-65 should be getting at least 30 minutes of moderate intensity activity five days of the week. Implementation of a physical activity program was shown to raise fitness, increase productivity and damp many health problems among workers.(15) The outcome of a physical fitness program for workers will be increased if properly designed with its different physical components by a


INTRODUCTION
Electromagnetic field (EMF) is determined by the force effect due to summation of electric and magnetic fields.It comprises a broad spectrum of non-ionizing radiation. (1,2)Extremely low frequency EMF is existing whenever electric wiring, electric Bull High Inst Public Health Vol.39 No. 1 [2009]   motors and electric devices are found.
Exposure may occur at home, at job and in electric vehicles.Workers in electric utilities and nearby power lines are at great risk. (1)e magnetic component of exposure is the suspicious part of low frequency EMF especially among electric utility workers.(3) On the other hand, high frequency EMF is another issue expressed as radiofrequency radiation which is present in many fields including mobile phones and their base stations.(4,5) Since the late part of the 20 th century there is increasing interest in the health effects of low frequency EMF especially in the form of subjective complaints including neurasthenic symptoms and sleep troubles, disturbances in cardiovascular and gastrointestinal functions and transient hematologic changes.(6) There are also, some existing concerns about childhood leukemias and certain types of cancer.(7) Metabolic parameters including cholesterol may be adversely affected due to exposure to low frequency EMF.(10)(11) Indices of magnetic field exposure were consistently related to mortality from arrhythmia.(3,11) Heart rate and heart rate variability may be affected by this exposure in a pattern suggesting the domination of sympathetic activity and imposing further cardiovascular risk.(12,13) Most of the reported health findings due to exposure to low frequency EMF seems to be related to workers' fitness and autonomic nervous control.(6) According to the latest guidelines, (14)   The level of significance of p was considered at 0.05.

Characteristics of the studied sample:
The There was significant reduction in total WBCs, basophils neutrophils, lymphocytes and monocytes after PAP compared to before (p= 0.041, 0.039, 0.000, 0.000 and 0.0013 respectively).Esionophils was the only significant parameter that showed an increase after PAP (p= 0.000).There were no significant differences for serum cholesterol level and other hematologic parameters.(Table 5) @ score from 0-10, where zero is no satisfaction at all and 10 is full satisfaction.

Discussion
The study sample was representative for workers exposed to low frequency EMF in an electrical utility.The exposure level was within the permissible limits. (22)The subjective symptoms reported by the studied sample before the PAP were high regarding sleep difficulties, headache and sense of easy fatigability.Answers ranged from yes to sometimes in almost more than half of the studied sample for all the tested parameters; meanwhile, cardiovascular and gastrointestinal symptoms were less frequently complained.However, subjective findings have been criticized for the lack of precision and the difficulty to establish a causeeffect relationship. (2,5) may be related to psychological aspect due to phobia from threats of exposure.It has been previously reported that low frequency EMF may increase the action of sympathetic nervous system on cardiovascular responses. (12,13,23) Bsed on our results, a PAP could be considered as a counteracting mechanism to the deleterious effects of low frequency EMF on cardiac autonomic control.This finding could be considered advantageous for the overall fitness of the worker, (16) as well as to reduce cardiovascular risk. (3)her risk factors that were studied in the present research were, SBP which showed significant reduction with the PAP;

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inspiration and expiration for 5 seconds each) to produce maximal R-R interval variation at a constant respiratory frequency.The ECG machine was operated at the standard rate of 25 mm/second.The intervals of the tracings were measured by a digitizer.The maximum R-R interval (R-R max) and the minimum R-R interval (R-R min) were identified in one minute.Sokolo-Lyon voltage (S-V1+ R-V5-6) was calculated as an index for left ventricular mass (LVM). (19)Venous blood sample was taken for analysis of total cholesterol by the standard methods.Another part of the sample, was kept unclotted (by adding EDTA) for complete blood count according to conventional methods, to include hemoglobin concentration (Hb), red blood cell count (RBC), packed cell volume (PCV), platelet count, total white blood cell count (WBC).Differential WBC count included percent basophils, esinophils, neutrophils, lymphocytes and monocytes.Physical activity program (PAP): A standardized program was designed by the experts in physical training according to the recommended guidelines. (16)The program time was 12 weeks, with a unit each week composed of 3 sessions.Each session is about 45 to 60 min and entails, warm-up, main part and cool-down.The main part of the physical activity program was directed for all body groups of muscles including neck, shoulders, arms, chest, trunk, abdomen, pelvis, back and lower limbs.Details of this program is mentioned elsewhere. (21)After program measurements: All data and investigations collected before were gathered again, including questionnaire, physiological and laboratory tests for comparison.Statistical analysis: Data was analyzed by SPSS package version 11.Mean quantitative values of before and after measurements were tested by t-test for difference in one group.Difference in qualitative variables was tested by X 2 test.Calculation of % change was done by the equation: % change =  −    X 100 The outcome of the PAP was for the favor of reduction of the frequently complained subjective symptoms.This may be attributed to the beneficial effect of physical activity on fitness, morals and general health.Similar results were found in other studies evaluating the possible effects of interventions with physical activity in health problems.(15, 16) The significant reporting of increase in health and work satisfaction after the PAP in our study is elucidating the general positive effects of physical activity.Workers exposed to EMF in the present study were overweight and obese according to their baseline mean BMI (above 25 kg/m2)(17)  and the PAP contributed significantly for their weight reduction.In the current study, a standardized PAP was administered to the workers and objective fitness outcomes were observed specially in the form of significant reduction in heat rate and increase in both R-R max and R-R min.These measures of heart rate variability pointed out to the favorable effect of this