Interactions of personal and occupational risk factors on hand grip strength of winter pruners
Introduction
Agriculture is a labour-intense working area and the working conditions are challenging in every step from seedbed preparation to post-harvest process. Agricultural workers are vital components in the process of agricultural production. High yield, high quality and sustainable production depends on the abilities of agricultural workers, their organization capability and handiness in operating various agricultural tools. During agricultural production, agricultural workers use various hand tools. Among these tools, hand-operated tools have an important place and are frequently used. These hand-operated tools imparts hand and forearm injuries and work-related problems (Sperling et al., 1993). Working with hand tools cause biomechanical stress and tension on upper extremities of the workers. Various studies conducted on this subject revealed a significant relationship between trauma-induced disorders and forceful exertions. This effect of the exertions manifests if they become more frequent and performed at awkward postures (Putz-Anderson, 1988). Agricultural production is one occupation where the forceful exertions are frequently used at improper postures.
Agricultural production usually involves outdoor activities; therefore, workers are directly affected by atmospheric conditions and work environments. Particularly, viticulture is an outdoor area of agricultural production activity with a high commercial value. One of the important processes that determine the productivity and quality of the vineyards is pruning. Winter pruning is the most prevalent pruning type and should take place during the period in which vine is in the dormant (sleep) period, in other words, between autumn, when leaves are shed, and spring, when buds are about to bloom (Yüksel et al., 2006). Timely and appropriate pruning directly affects the yield (Clingeleffer, 1984). Pruning time is regulated by the producers with consideration of the local conditions. Pruning should be performed by experienced workers; otherwise, product yield and quality will suffer. Expert pruners labouring in winter pruning work in teams. The teams investigate the vineyards in the working fields and pre-determine the pruning time and plan. On average, an experienced pruner works six hours a day and prunes approximately an area of 1000 m2 area.
Different hand tools are used in pruning, among these hand tools, the most important and common is pruning shears. Pruning shears is a human-powered hand tool and usually used unilaterally. Hand-friendly pruning shears and the working efficiency of blades are important in the productivity of pruners. The importance of the hand tool design in musculoskeletal and hand and forearm disorders was reported in a previous study (Mital, 1991).
When workers use non-ergonomic hand tools, they apply unnecessary force and/or adopt awkward postures for hands, wrists. If the upper extremities are repeatedly applied for the use of hand tools, an increase occurs in the risk of upper extremity musculoskeletal disorders (MSDs) such as, carpal tunnel syndrome, stenosing tenosynovitis, tendinitis etc. (Brickbeck and Beer, 1975; Masear et al., 1986; Silverstein et al., 1987; Kim, 2012; Fernandez and Marley, 2014). Thus, designing the proper hand tools for users is of great importance to reduce the risk of work-related MSDs. Along with repetition, awkward postures, vibrations, and forceful exertion were considered critical factors that caused MSDs resulting from the use of hand tools (Armstrong et al., 1990; Nazari et al., 2012; Dianat and Salimi, 2014).
Cumulative Trauma Disorders (repetitive motion injuries or work-related musculoskeletal disorders) are injuries to the musculoskeletal system that develop gradually as a result of repeated micro trauma due to poor design and the excessive use of hand tools such as pruning shears and other equipment. This naturally compels the pruner to choose the most comfortable shear during working. Therefore, different pruners use pruning shears of different brands and properties. It is essential for product designers to use anthropometric and hand grip strength data that are relevant and up to date when designing and developing products for pruners.
Grip force is applied to operate tools in many occupations that involve the hand/palm. It is a finger-flexion function that is activated by the finger flexors and forearms as well as intrinsic hand muscles (Maier and Hepp-Reymond, 1995). The GS is a reliable indicator of the muscle strength (Syddall et al., 2003). Hand GS can be measured with calibrated analog or digital dynamometers (Massy-Westropp et al., 2011). Since the GS measurements do not require any physical exertion, they are suited for measurements during pruning and allow monitoring the physical performance of the workers during the day (Samson et al., 2000).
Vineyard pruning is a relatively simple work of which growers seem to grasp fairly quickly. But the main target of pruning is to maintain a balance between vegetative growth and fruiting. Hence, the pruning should be done by professional pruners. The pruning work performs in different postures of pruners on continuous standing out position. Grip strength (GS) is applied to pruning shears in order to produce work. The hand/palm should press the upper-handle of the shear and finger flexion (Paivinen et al., 2000) should activate and clench the lower-handle of the shear (Fig. 1). This process is repeated many times during the work day. As a result of repetitive physical load (Roquelaure et al., 2001) and wrist movements (Roquelaure et al., 2002) at varying intensities, using pruning shears increase the risk of musculoskeletal discomfort. This leads the pruner to apply different GS, and consequently, show different pruning performances during the day.
Hand grip strength is associated with various factors. Age and gender of the workers were viewed as the primary factors that affect the GS, regardless of race and nationality (Ekşioğlu, 2016). Beside this, hand grip strength was determined to be in a strong correlation with some anthropometric properties, such as the weight, height and hand-length of the workers (Nicolay and Walker, 2005; Jurimae et al., 2009; Koley and Yadav, 2009; Dewangan et al., 2010; Gnaneswaran and Bishu, 2011; Ekşioğlu, 2016; Shurrab et al., 2017).
In the previous studies, the relationship between muscle strength and height, weight, age (Pascucci Sande et al., 2001; Nicolay and Walker, 2005; Kenny et al., 2008; Jurimae et al., 2009; Koley and Yadav, 2009; Dewangan et al., 2010; Tsubaki et al., 2010; Wimer et al., 2010; Kim et al., 2016; Ekşioğlu, 2016; Shurrab et al., 2017) and body-mass index (Corish and Kennedy, 2003; Kenny et al., 2008; Jurimae et al., 2009; Koley and Yadav, 2009; Ekşioğlu, 2016; Shurrab et al., 2017) of the workers were investigated. It was found that the muscle strength decreased with the increasing age. Decreasing-muscle measurements and GS values showed a positive correlation. Metter et al. (2002) found that the muscle strength started decreasing at the age of 50 and escalated after the age of 65.
This study focused on personal, physical (occupational), and environmental risk factors and their effect(s) on grip strength in an occupational cohort of Winter Pruners. Thus in this study to evaluate the effects of commonly used type of pruning shears, working ambient temperatures, work experiences of pruners, working hours, body mass index and some anthropometric values on total grip strength of professional pruners, and to suggest guidelines, based on this study, for the grip spans of combination pliers to hand tool users or designers, or both.
Section snippets
Participants
The study was conducted during the winter pruning in Sultanas’ vineyards located in Salihli/Manisa. In the experiment 18 healthy and professional pruners who had different years of pruning experience were selected at random to participate in the study and were monitored over eighteen workdays (December 2015–January 2016). The measurements were collected during the working hours. All of the pruners were male and their dominant hand was the right hand. Prior to the study, the pruners were
Results
The GS data of the pruners was measured for an 18-day period during winter pruning and evaluated for both hands. Descriptive statistics for the professional pruners were given in Table 3.
Discussion
In this study based on occupational cohort, it was shown that the effects of personally and occupational risks on hand grip strength of winter pruners.
Conclusion
The followings were concluded from the study conducted:
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GS of both hand decreases with increasing age of pruners.
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GS of the dominant hand had a greater value than that of the non-dominant hand.
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Although the correlation between anthropometric data and GS values was found not high enough, Anthropometric data and GS values from the pruners were found to be statistically significant.
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The type of the pruning shear affected the GS of the dominant hand.
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Ambient temperature and GS values of both hands
Acknowledgment
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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