Cardiovascular Strain of Bricklayers in Southwestern Nigeria

Transcription

1 Proceedings of the 2012 International Conference on Industrial Engineering and Operations Management Istanbul, Turkey, July 3 6, 2012 Cardiovascular Strain of Bricklayers in Southwestern Nigeria Olasunkanmi S. Ismaila Department of Mechanical Engineering Federal University of Agriculture P. M. B 2440, Abeokuta, Ogun State, Nigeria Kolawole T. Oriolowo Department of Mechanical Engineering The Polytechnic, Ibadan, Oyo State, Nigeria Olusegun G. Akanbi Department of Industrial Engineering University of Ibadan Ibadan, Oyo State, Nigeria Abstract The heart rate is commonly used to estimate the energy expenditure or physical strain in physically demanding job. The aim of this study was to assess the cardiovascular strain of bricklaying in South Western Nigeria using heart rate. Eighty Nine (89) Bricklayers with ages ranging from 16 to 60 years (mean = 33.7 years, SD = ±8.4 years) working on different building sites in Ibadan and Eruwa towns in Oyo State participated in the study. The resting heart rate ( H ) and working heart rate ( H W ) were measured with the use of a digital sphygmomanometer (POLYGON YS796). Cardiovascular strain was calculated. The results showed that the mean CVS was 57.4 % and since the average lies in the moderate range, bricklaying job required that action should be taken within the next few months. It was concluded that bricklaying could lead to cardiovascular strain on the workers, which may be reduced by redesigning the working system. It was recommended that lifting and motorized positioning devices should be provided in order to reduce strain due to carrying loads. Keywords Cardiovascular strain, Heart rate, bricklaying, Nigeria 1. Introduction Kumar (1991) observed that the fourth highest rate of lost-time claims due to sprains and strains was in the construction industry. Because bricklaying requires working above the shoulder and below the knee height, it has been considered to have ergonomic problem (Schneider and Susi, 1994). Samuelsson and Lundholm (2006) noted that the ergonomic problem in the construction industry could be because of heavy lifting, working on one side, and strenuous work postures. The job of the bricklayers involves the picking up of bricks (blocks) and places them in the wall, together with mortar (Luijsterb et al., 2005). The bricklayers lay between 800 and 1000 bricks (blocks), which are positioned between the place in which the bricks (blocks) are set out and the wall that is being built each workday. They also undertake other tasks such as setting out material, transportation, and communication. The bricks (blocks) are usually set out at ground level behind the bricklayers, which requires the bricklayers to bend and rotate their back about 800 times a day (Vink et al., 2002). Frequent bending and rotation of the trunk and lifting at work carries a high risk for back pain while disorders of the neck and shoulders can result from frequent bending of the neck and work with the arms elevated (Ariens et al., 2002). Boschman et al. (2011) listed the physical requirements of bricklayers job to include standing, lifting and carrying, repetitive movements, working above shoulders, working with a bent back, squatting and kneeling. The high level of 2022

2 manual handling, bending and rotation of the trunk, which is involved in bricklaying operations, exposed workers to higher levels of risks and high physical workload. In fact, Boschman et al. (2011) noted that the literature supports the perception that a bricklayer has a physically demanding occupation. Gogh (1990) found that excessive physical workload and heat stress were factors that could result in sudden unexplained death syndrome. Jung and Jung (2001) noted that from ergonomics perspective, occupational injuries and incidents are the result of poor task and work place design, which lead to errors, accidents and lower productivity. Larcher and Sohail (1999) noted that there are huge financial cost and human agonies associated with construction industry. There are efforts in both developed and industrially developing nations to investigate the impact of manual materials handling jobs on workers with a view to making such tasks bearable for workers, taking into consideration such parameters as energy intake, energy expenditure and physiological costs (Chung et al., 2005; Abe et al., 2004). Workers in most Nigerian establishments are recruited based on their performance at series of interviews coupled with aptitude tests. However, aptitude tests and interviews only cannot be appropriate to assess qualified manual workers to be employed for the manual tasks. The only major criterion for qualification for manual tasks is a minimum literacy level, and some technical know- how and some physical capabilities for their tasks. Industrial developments have resulted in a decreasing number of occupations that are physically strenuous in the traditional sense i.e. demanding intensive dynamic work with large muscle groups. At the same time, many jobs are stationary and use only one side of the body thus imposing static, combined static/dynamic and symmetric loads, especially on the arm-shoulder area. In Nigeria as in most developing countries, labour cost is cheap and most tasks are done manually such that physical demands of the task often exceed the physical capabilities of the worker (Scott & Christie, 2004). For a work to be compatible with the worker and enhance productivity, factors such as physical capabilities, health status, absence of accidents, absence of sickness and task performance are required (Sluiter and Frings-Dresen, 2007). Onethird of industrial back injuries could be reduced by designing the job to fit the worker (Snook, 1978). It is essential therefore to evaluate the physiological workload of bricklaying operations. Many ways have been adopted in measuring workers, responses to manual tasks in order to appraise the incompatibility of work demands to the capabilities of the workers. Heart rate is commonly used to estimate the energy expenditure or physical strain during sports, work or daily activities (McArdle et al., 2001; Bot and Hollander, 2000; Haskell et al., 1992). Past researchers have used elative Heart ate (Ismaila et al., 2012; Wu and Wang, 2002; Kirk and Sullman, 2001) and elative Cardiovascular Load (Intaranont and Vanwonterghem, 1993; Yoopat et al., 2002) as indicators of physical workload that is related to muscular activities. The present study proposes the use of Cardiovascular Strain for the assessment of bricklaying jobs in terms of physical workload using the heart rate. 2. Methodology The field study was conducted at building sites in Ibadan and Eruwa in Oyo state of Nigeria. Eighty Nine (89) bricklayers with ages ranging from 16 to 60 years (mean = 33.7 years, SD = ±8.4 years) working on different building sites participated in the study. The Heart ates (H) of each worker were measured with the use of a digital sphygmomanometer (POLYGON YS796). The resting heart rate was measured by asking the subject to sit down quietly for five minutes and then measuring the resultant heart rate. Working heart rate was measured while the bricklayers were working over a one-hour period that did not include breaks. The cardiovascular strain was determined using the following relationship: Cardiovascular Strain (CVS) = Change in heart rates (1) Original heart rate This is premised on the fact that Strain = Change in length (Shigley and Misschke, 2005) (2) Original length The cardiovascular strain (CVS) was therefore determined as the ratio of change in heart rates to the initial (resting heart rate) as stated in (3) HW H CVS = 100 (3) H Where H W = working heart rate and H = resting heart rate 2023

3 In the determination of the classification of CVS, the Heaviness of work (Kroemer et al., 2000) and work intensity by Astrand and odahl (1986) were considered. (Kroemer et al., 2000) defined heaviness of work as: Light work: 90 beats per minute; Medium work: 100 beats per minute; Heavy work: 120 beats per minute; Very heavy work: 140 beats per minute; Extremely heavy work: 160 beats per minute. Astrand and odahl (1986) classified work intensity as light (H W <90); moderate (90 H W <110); heavy (110 H W <130), very heavy (130 H W <150) and extremely heavy (150 H W < 170). The averages of CVS using both the categorizations of Kroemer et al. (2000), Astrand, and odahl (1986) were used for the classification of CVS as follows: (i) 0-33%: Acceptable range and there is no action required (ii) 34-63%: Acceptable range and there is no action required (iii) 64-93%: Moderate range and action is required within the next few months (iv) %: High range and action is required within the next few weeks (v) %: Very high range and action is required within the next few days (vi) : Too high range and action is required immediately 3. esults Table 1 shows the anthropometric characteristics of the bricklayers. The mean height of the bricklayers that were studied was 1.6m while their mean age was 33.7 years. The mean Body Mass Index (BMI), a measure of obesity and defined as weight in kilograms divided by height in metres squared was 22.7 Kg/m 2.with a range of 17 and 33.1 Kg/m 2. Using the criteria for obesity that for non-obese, the BMI should lie between 18.5 and 24.9 kg/m 2, 35 and 39.9 kg/m 2 for moderately obese and more than 40 kg/m 2 for extremely obese (Singh et al., 2009), some of the workers were underweight while none was obese. Table 1: Summary of Anthropometric Characteristics of the bricklayers Percentiles 5 th 50 th 95 th Min Max Mean SD Height (m) ± 0.1 Age (Years) ± 8.4 Weight (Kg) ± 6.1 BMI (Kg/m 2 ) ± 3.4 H est (bpm) ± 8.3 H Work (bpm) ± 15.7 CVS ± 32.3 The mean resting heart rate was 68.6 beats per minute and it ranged between 53 and 92 beats per minute while the mean work heart rate was beats per minute ranging from 94 to 157 beats per minute. The mean heart rate (120.8 bpm) needed to do bricklaying work in the present study was above the recommended limit of 110 bpm for an 8-hour work shift (Sanders and McCormick, 1993; Saha et al, 1979). The result of the present study differs from the work of Astrand (1967) which found a mean heart rate for 10 bricklayers as 97.9 bpm (SD = ± 9.5 bpm). The difference in the two studies may be because of the number of subjects involved as the present study used 89 bricklayers. The mean CVS was 78.6 % with a range of between 11.1 and %. With the categorization earlier mentioned, bricklaying job on the average lies in the moderate range and action is required within the next few months. This is in contrast with the study of Jørgensen et al. (1991) which, described bricklaying as heavy work. The difference in the conclusions of the two studies could be due to the experience of the bricklayers involved. Bricklayers usually work in places where their freedom of movement is restricted which forced them to adopt awkward, twisting movements when lifting and laying blocks resulting in increases of the risk of musculoskeletal 2024

4 injury. They also work against gravity in awkward posture, which further results in high musculoskeletal loads and reduces blood flow to muscle and other tissue. These activities require high-energy expenditure with resultant increase in cardiovascular strain. As noted by Ismaila et al. (2011), bricklayers require high resting period to reduce muscular fatigue that could set in and the resultant pain after the day s job. There would be the need to redesign the work methods to reduce the incidence of muscular discomfort associated with this workload. The use mechanical of equipment is necessary to reduce the force needed to lift, carry, move, hold or restrain material and tools. In fact, van der Molen et al. (2004) proposed the use of mechanised transport to reduce the frequency of handling objects. Some other recommended job-specific interventions for bricklayers were the use of a scaffolding console to reduce the frequency and duration of trunk flexion during bricklaying (van der Molen et al., 2004; Vink et al., 2002). There is also the need to change work practices or equipment to avoid repetitive actions or prolonged tasks. 4. Conclusions The work contents of bricklaying are above the recommended value and could lead to cardiovascular strain on the workers, which may be reduced by redesigning the work system. There is therefore the need to redesign the workplace and work method to reduce the work stress factor. It is recommended that lifting and motorized positioning devices should be provided in order to reduce strain due to carrying loads. Manual workers should be tested and evaluated for their fitness for a particular task, and their working time optimized without discomfort, to harness maximum efficiency of the worker for the designated operation, which will increase output. eferences 1. Abe, D., Yanagawa, K..., and Nihata, S., Effects of load carriage, load position and walking speed on energy cost of walking. Applied Ergonomics, vol. 35, pp , Ariens, G. A. M., Bongers, P. M., Hoogendoorn, W. E., van der Wal, G., van Mechelen, W., High physical and psychosocial load at work and sickness absence due to neck pain. Scandinavian Journal of Work, Environment and Health, vol. 28, no. 4, pp , Astrand, P. O., and odahl, K., Textbook of Work Physiology: Physiological Bases of Exercise. 3rd Edition. New York: McGraw-Hill Book Company, Boschman, J. S., van der Molen, H. F., Sluiter, J. K., Frings-Dresen, M. H., Occupational demands and health effects for bricklayers and construction supervisors: A systematic review. American Journal of Industrial Medicine, vol. 54, pp , Bot, S. D. M., and Hollander, A. P., The relationship between heart rate and oxygen uptake during nonsteady state exercise. Ergonomics, vol.43, no. 10,pp , Chung, M. K., Yue, J. L., Inseok, L., and Kyung, I. C., Physiological workload evaluation of carrying soft drink beverage boxes on the back. Applied Ergonomics, vol.36, pp , Gogh, K. T., Sudden unexplained death syndrome among Thai workers in Singapore. Paper presented at the National Epidemiology Seminar, Bangkok, Thailand, Haskell, W. L., Yee, M. C., Evans, A. and Irby, P. J., Simultaneous measurement of heart rate and body motion to quantitate physical activity. Medical Science Sports Exercise, vol. 25, , Intaranont, K., and Vanwonterghem, K., Study of the exposure limits in constraining climatic conditions for strenuous tasks: An ergonomic approach. Unpublished manuscript, European Commission (DGXII TD), Brussels, Belgium Ismaila, S. O., Oriolowo, K. T., and Akanbi, O. G., Work capacity assessment of Nigerian bricklayers, Management Science Letters, vol. 2, pp , Ismaila, S. O., Oriolowo, K. T., and Akanbi, O. G., Energy Expenditure equirements of Bricklaying in South Western Nigeria. Proceedings of Human Factors in Organizational Design and Management-X, Grahamstown, South Africa 4-6 April, 2011, M. Gobel, C.J. Christie, S. Zschernack, A.I. Todd and M. Mattison (Eds.) II. Published by Department of Human Kinetics and Ergonomics, hodes University, Grahamstown, South Africa, pp , Jørgensen, K., Jensen, B.., and Kato, M., Fatigue development in the lumbar paravertebral muscles of bricklayers during the working day. International Journal of Industrial Ergonomics, vol. 8, pp , Jung, H. S., and Jung, H., Establishment of overall workload assessment technique for various tasks and workplaces. International Journal of Industrial Ergonomics, vol. 28, pp ,

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