Linkage between machine power utilization and ergonomics,with reference to reducing exertions at work

Abstract

BACKGROUND:

Despite mechanization development, leafy vegetable cultivation (LVC), as a labor-intensive activity in both developed and developing countries, still suffers from heavy physical activities.

OBJECTIVE:

The present study evaluated the human physiological strains of LVC’s workers to identify relationships among contributing factors affecting human physiological strains.

METHODS:

Thirty male workers were included in this study. Working heart rate (HR) was measured using a heart rate sensor during various operations. The time taken to treat a known area was measured using a stopwatch to calculate work speed (or field capacity (FC)) for each operation. Pearson correlation coefficient and linear regression were used to investigate the relationships among HR, heart rate ratio, FC and mechanization status (MS), and human energy expenditure rate and total energy expenditure per unit area.

RESULTS:

The highest HR was at seedbed preparing (120.1 beats/min) and lowest at manual harvesting (87.8 beats/min). Manual hoe-used operations (seedbed preparing, manure application and irrigating) were demonstrated as the critical operations concerning physiological strains. The operations performed by machine power corresponded to a high FC.

CONCLUSIONS:

Variables influencing the area treating speed (i.e. MS and FC) are negatively linked to the human energy consumed per unit area and variable changed in time unit (i.e. HR) was positively linked to the human energy expenditure speed.

Keywords

Agricultural mechanization leafy vegetable cultivation field capacity worker human energy expenditure

1 Introduction

Small scale farming is a common activity even in developed countries [1]. Leafy vegetable cultivation (LVC) on small scale is frequently observed in Iran, whereas official statistics are not available in this case. About thirty percent of fruit and vegetable export tonnage of Iran owes to the vegetables, with considering fruit and vegetable trade income of about 1300 million US dollars [2]. However, farmers’ migration to urban areas is growing. Because of this, the improvement or even saving the current status of agricultural production and trade suffers from problems specially LVC production in Iran [3].

To deal with a part of problems in agriculture, mechanization has been employed in the last decades. Agricultural mechanization has functions such as the improvement of product yield and work speed (for example, the speed of treating field area) and reduction in costs as well as considering worker’s occupational health and safety [3, 4]. Mechanization has been successful in surmounting many difficulties in agricultural sectors related to yield, work speed and costs. For example, mechanized milking methods have a higher cow milked per man-hour and a lower costs per one kg extracted milk than manual method about 250% and 32% respectively [5]. The productivity for the new motorized fresh oil palm fruit bunch cutter was 39.4% better than the manual cutting [6]. Mechanization has brought a wide range of occupational health and safety outcomes. For example, in the mentioned study [6] motorized cutter reduced the weight of the harvesting pole from 7.5 kg to 6.5 kg which subsequently decreased the fatigue on the manual labors, whereas they suffered from high vibration of these tools [7]. An ergonomic study investigated the anthropometric data of Iranian tractor drivers and revealed that the numbers of steps of tractors are low and their heights from the ground surface are high. Besides, the seat depth of some tractors was great for drivers in the 5th percentile value [8] which may cause the body discomfort. Tractor drivers also suffer from psychoacoustic annoyance due to tractor sound [9]. The energy expenditure was lower with mechanized date fruit stripping methods in comparison with the traditional method, although, neck discomfort was created when using mechanized methods [10]. Although there are the advantages and disadvantages of mechanization concerning worker’s occupational health and safety, addressing the health and safety principles in the design of mechanized tools has been advised and mechanization has been considered as a cause of reducing the occurrence of occupational risk factors [11, 12].

Occupational risk factors due to labor-intensive and high physically demanding activities are prevalent in agricultural sectors [13 –15]. These activities are often associated with workloads and unsuitable positions for workers [16 –19] that may hurt workers’ health [20]. Poorly designed manually operated hand tools and equipment are utilized in awkward postures [21]. Workers have to do physical effort [22] which demands excessive energy [23]. Thus, the workers get fatigued which results in body pain, musculoskeletal disorders and physiological strains [24]. Excessive stooped and squatting postures as the most common awkward postures in traditional sesame seed and saffron harvesting increase the risk of low back disorders [17, 25]. Laborers have to experience high physiological efforts to do hand cow milking [26]. Pineapple cultivation consists of high numbers of manual operations that expose workers to a great number of risk factors such as snack attacks [27].

Vegetable cultivation in both developed and developing countries is connected with hazardous works, awkward postures and heavy physical efforts [28]. Frequently working tasks at ground level in harvesting radish caused the prevalence of low back and knee complaints [29]. Workplace at the ground level is sometimes associated with stooping posture as is a common manual agricultural activity during sickle weeding in developing countries [30]. Frequently performing these activities exposes workers to the development of musculoskeletal disorders [31]. Women workers face severe health hazards in picking vegetables in terms of cuts and wounds in hands [23]. Generally, about half of vegetable workers suffer from occupational injuries [32].

The vegetable production chain had a low level of mechanization. The improvement of the mechanization level may have an important role in the increase in vegetable production and keeping the health of employed workers. To gain it, we must initially understand which activities demand high physical efforts. Heart rate and human energy expenditure are the appropriate methods to identify physical efforts [33, 34]. Therefore, LVC’s activities that are physiologically critical onerous should be identified. We need an understanding of causal linkages between risk factors and outcomes of human physiological strains in LVC. Then, we can decide to introduce improved methods such as mechanization and ergonomic interventions.

Studies [16 , 35] have shown the excessive physiological strains measured using cardiorespiratory stresses and human energy expenditure in agricultural works, such as weeding at vegetable farms and cow milking, in which human power is extensively used. Researches [29, 36] reported that the level of mechanization and intensity of operation affects the physiological demand of agricultural workers in rice cultivation and vegetable farms. Therefore, a better mechanization level may affect the mitigation of the human physical effort, encourage the laborers and farmers to withdraw from migration and the increase in vegetable production. Some agricultural tools and ergonomic interventions are designed and employed for vegetable cultivation in the world [14 , 28], but there is no completely suitable suggestion for workers of LVC in Iran. Maybe there would be some reasons such as non-coverage of all the LVC tasks, cost of interventions, problems around adoption and cultural conflicts. The present study was undertaken to physiologically evaluate the LVC tasks to identify the human effort required to do them and causally investigate predictor and outcome factors.

2 Material and methods

2.1 Leafy vegetable cultivation

Some of the leafy vegetables were fenugreek (Trigonella foenum-graecum L.), parsley (Apium petroselinum L.), chard (Beta vulgaris var cicla L.), dill (Anethum gravealens L.), and spinach (Spinacia oleracea L.) which are cultivated in Iran from September to March. The operations to cultivate these crops are moldboard plowing (using tractor), disking (as the second plowing using tractor), seedbed preparing (using manual hoe), manure application (using manual hoe and wheelbarrow), chemical fertilizer broadcasting (using hands), seed broadcasting (using hands), irrigating (using manual hoe), spraying (using lever-operated knapsack sprayer), and manual harvesting (using manual sickle). Table 1 shows the work details of LVC operations and their mechanization status (MS). Operations performed using machines were considered as mechanized operations, and operations performed using hands and/or manual tools were considered as manual operations. Being mechanized or manual was introduced as MS of an operation. The lever-operated knapsack was accounted as a manual tool [37] and consequently, its relative operation (spraying) was allocated in manually performed operations. During spraying, the weight borne by workers decreased through spending time from 20 kg (fully-loaded sprayer) to at least 3 kg (empty sprayer). The study was conducted in the southwest of Iran and participants were selected among workers of LVC in the southwest of Iran.

Table 1
Most common jobs and work elements in operations of leafy vegetable cultivation

Operation Most common jobs Most common work elements

Moldboard plowing^* Driving the tractor Sitting on the tractor’s seat, arm and foot movements to use levers and pedals

Disking^* Driving the tractor Sitting on the tractor’s seat, arm and foot movements to use levers and pedals

Seedbed preparing^ Cutting the soil and reversing it Standing; using force (on the soil) using manual hoe; lifting the load (soil) and reversing it using a manual hoe

Manure application^ Transferring a wheelbarrow full of manure to the field; distributing the manure on the plot Loading manure into wheelbarrow using manual hoe; lifting wheelbarrow handles; moving loaded wheelbarrow; strewing a load (manure) in the plot using a manual hoe

Chemical broadcasting^ Distributing the chemical granules throughout the plot Stooping with walking and strewing load (chemical granules) less or up to 1.5 kg

Seed broadcasting^ Distributing the seed throughout the plot Stooping with walking and strewing load (seeds) less or up to 1.5 kg

Irrigating^ Closing and opening the water channels Standing; using force (on the soil) using manual hoe; lifting a load (soil) using manual hoe; carrying the load (soil) using a manual hoe to another place

Spraying^ Herbicide application on the vegetable plots Walking with lifting and carrying the load (lever-operated knapsack sprayer) throughout the vegetable plot

Manual harvesting^** Mowing the vegetables Crouching with squatting; cutting the vegetables using a manual sickle

Operation	Most common jobs	Most common work elements
Moldboard plowing^*	Driving the tractor	Sitting on the tractor’s seat, arm and foot movements to use levers and pedals
Disking^*	Driving the tractor	Sitting on the tractor’s seat, arm and foot movements to use levers and pedals
Seedbed preparing^**	Cutting the soil and reversing it	Standing; using force (on the soil) using manual hoe; lifting the load (soil) and reversing it using a manual hoe
Manure application^**	Transferring a wheelbarrow full of manure to the field; distributing the manure on the plot	Loading manure into wheelbarrow using manual hoe; lifting wheelbarrow handles; moving loaded wheelbarrow; strewing a load (manure) in the plot using a manual hoe
Chemical broadcasting^**	Distributing the chemical granules throughout the plot	Stooping with walking and strewing load (chemical granules) less or up to 1.5 kg
Seed broadcasting^**	Distributing the seed throughout the plot	Stooping with walking and strewing load (seeds) less or up to 1.5 kg
Irrigating^**	Closing and opening the water channels	Standing; using force (on the soil) using manual hoe; lifting a load (soil) using manual hoe; carrying the load (soil) using a manual hoe to another place
Spraying^**	Herbicide application on the vegetable plots	Walking with lifting and carrying the load (lever-operated knapsack sprayer) throughout the vegetable plot
Manual harvesting^**	Mowing the vegetables	Crouching with squatting; cutting the vegetables using a manual sickle

^*Refer to process performed using machine power. ^**Refer to process performed manually.

2.2 Participants

Thirty male workers were recruited for this study (Table 2). Among thirty workers, eight were tractor drivers and twenty-two performed various tasks with manual tools. All the workers regularly worked in the cultivation of leafy vegetables and had at least ten years of work experience in LVC. Their body build was “normal” based on body mass index classification [38]. The workers were right-handed and free of medication. Consent from the workers was obtained and the experimental protocol was explained before the experiments.

Table 2
Background of workers of leafy vegetable cultivation

Operations Tractor drivers Manual workers

No. 8 22

Age (years) 46 (±3) 25 (±5)

Weight (kg) 62 (±8) 70 (±6)

Height (cm) 168 (±9) 177 (±12)

Body mass index (kg/m²) 22 (±4) 22 (±3)

HRrest (beats/min) 68 (±7) 60 (±4)

Operations	Tractor drivers	Manual workers
No.	8	22
Age (years)	46 (±3)	25 (±5)
Weight (kg)	62 (±8)	70 (±6)
Height (cm)	168 (±9)	177 (±12)
Body mass index (kg/m²)	22 (±4)	22 (±3)
HRrest (beats/min)	68 (±7)	60 (±4)

2.3 Measurements

Working heart rate (HR) and heart rate ratio (HRR) were considered as physiological indexes. Heart rate was measured using a Beurer PM 45 (Beurer, Germany). The heart rate signals were transferred from the transmitter put on the chest to the monitor put on the worker’s wrist. Heart rate was recorded during various operations. Heart rate at rest (HRrest) was measured for 5 min while the worker was resting in the supine position [39]. Maximal heart rate (HRmax) was calculated as [40]: $HR max = 205.8 - 0.685 \times Age$

HRR was calculated with the following equation [41]: $HRR = 100 \times (HR - HRrest) / (HRmax - HRrest)$

The human energy expenditure rate (EE) during works was obtained using the following equation for males in kJ per min [42]: $\begin{matrix} EE = 55 . 0969 + 0 . 6309 \times HR + 0 . 1988 \times Weight + 0 . 2017 \times Age \end{matrix}$

Total energy expenditure per unit area (TEE) in MJ per hectare (MJ/ha) was calculated as follows: $TEE = (EE / FC \times 60) / 1000$

Where FC (field capacity) is the speed of field treated for various operations and is often presented in hectare per hour (ha/h). To calculate FC for each operation, the time taken to treat a known area was measured using a stopwatch. TEE was calculated disregarding the number of repetitions for an operation. Seasonal energy expenditure for each operation (SEE) was calculated with multiplying TEE by the number of repetitions of that operation [36]. All the measurements were performed at temperatures varied between 16°C and 39°C in the morning.

2.4 Statistical analysis

To identify human physiological-based critical operations and casual relationships between factors taking part in human physiological indexes, some statistical analysis was conducted. Analysis of variance (ANOVA) and Duncan’s multiple range tests were used to statistically compare means. A value of p < 0.05 (two-tailed) was considered as the statistical significance level. Linear regressions were calculated by considering predictor and outcome factors in LVC concerning human physiological strains. MS of mechanized and manual operations was entered in regression as 1 and zero respectively. Before the establishment of regressions, correlations between predictors and outcomes were investigated to identify significant correlations. Only predictors that had a significant correlation with outcomes were entered in regression. If both HR and HRR variables had a significant correlation with outcome simultaneously, the variable that had a higher correlation coefficient was entered in regression [36]. Pearson correlation coefficient was used to investigate the correlations. Statistical analysis was conducted using IBM SPSS Statistics 24 (IBM Corporation, USA).

3 Results

As shown in Table 3, FC in machine-powered operations was significantly higher than manual operations. HR, HRR, EE and TEE of seedbed preparation were highest compared with their corresponding values in other operations at the 0.05 level of significance. Manure application and irrigation were respectively after the seedbed preparing, concerning HR, HRR, and EE. Considering the number of repetitions of operations in one cultivation season, it showed that the highest human energy expenditure in hectare during one season belonged to manual harvesting which took 67.5% of the total human energy required in one season (Table 4).

Table 3
Physiological strains of workers in different operations of wintry leafy vegetable cultivation¹

Processes FC (ha/h) HR (beats/min) HRR (%) EE (kJ/min) TEE (MJ/ha)

Moldboard plowing 0.6404^b 92.6^de 20.6^f 23.7^de 2.2^d

Disking 0.9610^a 93.0^d 19.6^f 22.9^de 1.4^d

Seedbed preparing 0.0033^e 120.1^a 47.6^a 40.7^a 743.2^a

Manure application 0.0042^e 114.6^b 41.9^b 36.3^b 514.1^c

Chemical broadcasting 0.3574^c 95.2^d 29.0^d 25.1^d 4.3^d

Seed broadcasting 0.3615^c 93.5^d 26.8^de 23.3^de 3.9^d

Irrigating 0.0288^e 107.2^c 37.3^c 32.5^c 71.9^d

Spraying 0.2464^d 96.1^d 28.6^d 25.2^d 6.2^d

Manual harvesting 0.0022^e 87.8^e 22.7^ef 20.2^e 591.8^b

Processes	FC (ha/h)	HR (beats/min)	HRR (%)	EE (kJ/min)	TEE (MJ/ha)
Moldboard plowing	0.6404^b	92.6^de	20.6^f	23.7^de	2.2^d
Disking	0.9610^a	93.0^d	19.6^f	22.9^de	1.4^d
Seedbed preparing	0.0033^e	120.1^a	47.6^a	40.7^a	743.2^a
Manure application	0.0042^e	114.6^b	41.9^b	36.3^b	514.1^c
Chemical broadcasting	0.3574^c	95.2^d	29.0^d	25.1^d	4.3^d
Seed broadcasting	0.3615^c	93.5^d	26.8^de	23.3^de	3.9^d
Irrigating	0.0288^e	107.2^c	37.3^c	32.5^c	71.9^d
Spraying	0.2464^d	96.1^d	28.6^d	25.2^d	6.2^d
Manual harvesting	0.0022^e	87.8^e	22.7^ef	20.2^e	591.8^b

¹In each column, values followed by the same letters are not significantly different at the 0.05 level of significance.

Table 4

Physiological strains of workers in different operations of wintry leafy vegetable cultivation

Processes	Number of repetitions during the season	TEE (MJ/ha)	SEE (MJ/ha)	The proportion of SEE (%)
Moldboard plowing	1	2.2	2.2	0.0362
Disking	1	1.4	1.4	0.0233
Seedbed preparing	1	743.2	743.2	12.0362
Manure application	1	514.1	514.1	8.3444
Chemical broadcasting	3	4.3	12.8	0.2070
Seed broadcasting	1	3.9	3.9	0.0626
Irrigating	10	71.9	718.5	11.6629
Spraying	1	6.2	6.2	0.1011
Manual harvesting	8	591.8	4158.4	67.4992
Total			6160.7	100.0000

According to the regression analysis shown in Table 5, HR variations could explain EE variations, but MS was unable to do it. Based on results (Table 3), the variation of HR from one operation to another is often associated with variation of EE in the same direction, but this order didn’t establish between MS and EE variations. For example, manual harvesting had a lower HR and EE in comparison with seedbed preparing, but it was the same as seedbed preparing, concerning MS. Table 5 showed that with a 1% variation of HR, EE varied 2.4608% in the same direction (HR’s Elasticity = 2.4608).

Table 5

Estimated regression coefficients for EE

Variables	β	Standardized coefficients β	T	Sig.	Elasticity
Constant	–37.374		–23.688	0.000
HR	0.651	0.976	42.380	0.000	2.4608
MS	0.285	0.014	0.618	0.538

Model summary: R² = 0.944; Adjusted R² = 0.943; F = 980.432; Sig.: 0.000

In addition to already mentioned independent variables, the other variables that may scientifically affect the dependent variable should be entered through estimating regression. Therefore, to estimate a regression to determine the significant independent variables capable of explaining the TEE variations, the effect of MS on FC (MS×FC) was considered due to the reports of agricultural mechanization studies [3]. Results of regression estimated for TEE showed that HR variations could not explain TEE variations, but MS, FC, and MS×FC could do it (Table 6). Regression estimation showed the negative link between MS and FC (as independent variables) and TEE variations. MS×FC had the highest effect on the TEE among other independent variables (Standardized β= 1.442).

Table 6

Estimated regression coefficients for TEE

Variables	β	Standardized β	T	Sig.	Elasticity
Constant	229.180		1.209	0.229
HR	2.067	0.084	1.169	0.245
MS	–1307.008	–1.378	–8.969	0.000	–157.2000
FC	–411.435	–0.554	–2.101	0.038	–47.9401
MS×FC	1297.357	1.442	4.684	0.000

Model summary: R² = 0.552; Adjusted R² = 0.537; F = 35.438; sig.: 0.000.

4 Discussion

In the present study, each operation was considered as a whole, because the outcome of the operation was important for us. In a study performed on the rice cultivation, each operation had been broken down into subtasks when expressing the results, for example, straight driving and cornering were considered for the first plowing [36]. Moreover, an operation may be changed wholly by introducing a suggested tool or an ergonomic intervention. The results of physiological stresses showed that LVC is a moderate activity according to a classification based on heart rate [43] and all its operations have a higher EE in comparison with domestic operations ranged from 8.2 to 12.0 kJ/min [36].

At the operations of moldboard plowing and disking, performing light work elements (i.e. sitting on the tractor’s seat, and arm and foot movements to use levers and pedals respectively) could explain the low value of time-based human physiological strains (HR, HRR, and EE). Also, the high value of FC for these two operations could explain the low value of area-based human energy expenditure (TEE). Therefore, the utilization of a machine (tractor) caused the low value of human physiological strains. The use of animal-powered plowing resulted in a lower EE 12.3 kJ/min [44] compared with the present study. However, EE of tractor driving was approximately twice as much as one reported by another study [45] for Iranian workers (11.7 kJ/min).

Operations performed using manual hoe showed higher time-based human physiological strains compared to other operations, which could be identified as the most critical operation in LVC concerning the physiological aspects. These operations were, in descending order, seedbed preparing, manure application, and irrigation. In the case of area-based human energy expenditure, this order was disturbed. It could be because the order of FC of operations was different from that of time-based physiological strains of operations. Seedbed preparation had the highest area-based human energy expenditure and could be identified again as the physiologically most critical operation in LVC. Seedbed preparation has been named “hoeing” in some studies. EE of this operation was observed higher than other studies for both womenfolk (16 kJ/min) and male workers (21.3 kJ/min) [44, 45].

The processes of chemical and seed broadcasting were manually performed, without any machine and tool; the worker only bore a little strain due to the need for a little force for the carriage of the bag full of seed or chemical fertilizer, and for distributing them using his hands. These bags weighed at most 1.5 kg when full-loaded. In a study in which seed and chemical fertilizer broadcasting were performed using a knapsack type powered broadcaster [36], HR of seed broadcasting (122 beats/min) and chemical fertilizer broadcasting (138 beats/min) were found to be higher than corresponding values reported in the present study. Higher HR in the mentioned study may be due to the workers carried a heavier load (at least 12 kg). A manual-powered operation probably has a lower physiological strain than a mechanically-powered operation as reported by some researchers [35, 46].

Participants of the present study used lever-operated knapsack sprayer, as a manual tool. Their mean HR was 96 beats/min which was less than mean HR (130 beats/min) measured for this operation in a former study in which a knapsack powered blower was used [36]. Its weight was 29 kg to at least 12 kg, which was heavier than the knapsack sprayer of the present study (20 kg to at least 3 kg). The heavier weight of knapsack powered blower in comparison with lever-operated knapsack sprayer may be a reason for higher HR among users.

Traditional irrigation in Iran is carried out with opening and closing channels [47] which was also performed in the present study. A higher EE was obtained in the present study as compared with that of Brun and colleagues’ study (17.6 kJ/min) [47]. This difference of EE between our and their study could be due to differences in the methods used for the measurement of EE. However, both studies classified it as moderate work concerning physiological strains.

Mowing the vegetables in manual harvesting was performed in crouching with a squatting posture and did not require high force. It might be a reason for the fact that HR, HRR, and EE during manual harvesting were lower in comparison with many of the operations studied in the present study. Perhaps, due to a low FC, this operation had second high TEE next to the seedbed preparation. A high number of repetitions (8 times harvesting per season) could explain the high value of SEE. EE recorded for manual harvesting (20.2 kJ/min) was lower compared with cutting straw with bend forward posture (23.4 kJ/min) and higher than manual sorghum harvesting with standing posture (10 kJ/min) [45]. Weeding operation by manually operated sickle in the study of Yadav and colleagues [35] was done very similar to manual harvesting in the present study. The average HR of male weeding laborers in that study (129.2 beats/min) was higher than the HR of manual harvesters in the present study (87.8 beats/min). This difference may be explained by the difference in climate conditions.

Some manual operations (seed broadcasting, chemical fertilizer broadcasting, and spraying) were statistically equaled to mechanized operations (moldboard plowing and disking) concerning EE. Even, more mechanized weeder with twin wheel hoe had a higher EE compared with traditional weeding equipment (a short-handled cutting tool with a flat blade) by 32% in soybean cultivation in India [48, 49]. It could be a reason for the fact that MS was unable to explain EE variations as it had been shown in the regression. This implied that the mechanization status was not necessarily linked to time-based human energy expenditure (EE).

Results showed that FC was remarkably affected by mechanization as reported in former researches [3]. It resembled that of the aforementioned study [48] in which FC of more mechanized weeding is 1.7 times greater than that of traditional weeding. FC is defined as the number of treated trees in a given time in the pollination of date palm trees. In the date palm cultivation, FC of pollination by a mechanized device was two times higher than the FC of a traditional pollination method [50]. However, mechanization has not reduced the number of complaints and new problems arise due to the changing working environment [51].

The operations performed by machine power had the highest FC. Some of the manually performed operations were accounted as low TEE operations and some of them not, but all the machine powered operations were accounted as low TEE operations. This result is in line with those of Nawi et al. [36], where a low FC corresponded to high-energy expenditure for an operation.

The present study has certain limitations. Women usually do not perform heavy operations in LVC and they perform light works such as manual harvesting in Iran. Females could not take part in this study due to cultural concerns. Further studies are required with the inclusion of female workers besides male ones for more generalizability of findings because males may have a higher physical capacity in comparison with females and it may affect the results. Besides, there was a possibility of the Hawthorn effect in the measurement of FC.

5 Conclusion

In the case of leafy vegetable cultivation:

Manual hoe-performed operations were demonstrated as physiologically critical operations.

The variables influencing the area treating speed (i.e. mechanization status and field capacity) were negatively linked to the area-based human energy expenditure. While variables changed in time unit were positively linked to the human energy expenditure speed.

Mechanized operations and field capacity improvement did not absolutely cause a reduction in human energy expenditure speed, but could negatively be linked to human energy expenditure per area treated.

Conflict of interest

None to report.

Footnotes

Acknowledgments

The authors wish to thank the volunteer workers for participating in the study, Dr. Abbas Abdeshahi for his assistance in statistical analysis and Prof. Krishna N. Dewangan for the technical editing of the paper.

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Linkage between machine power utilization and ergonomics,with reference to reducing exertions at work

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1 Introduction

2 Material and methods

2.1 Leafy vegetable cultivation

Table 2 Background of workers of leafy vegetable cultivation Operations Tractor drivers Manual workers No. 8 22 Age (years) 46 (±3) 25 (±5) Weight (kg) 62 (±8) 70 (±6) Height (cm) 168 (±9) 177 (±12) Body mass index (kg/m2) 22 (±4) 22 (±3) HRrest (beats/min) 68 (±7) 60 (±4)

2.4 Statistical analysis

3 Results

5 Conclusion

Conflict of interest

Footnotes

Acknowledgments

References

Table 2
Background of workers of leafy vegetable cultivation

Operations Tractor drivers Manual workers

No. 8 22

Age (years) 46 (±3) 25 (±5)

Weight (kg) 62 (±8) 70 (±6)

Height (cm) 168 (±9) 177 (±12)

Body mass index (kg/m²) 22 (±4) 22 (±3)

HRrest (beats/min) 68 (±7) 60 (±4)