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. 2025 Sep 30;15:33758. doi: 10.1038/s41598-025-00144-w

Muscle fatigue assessment using surface electromyography in farm operations performed in protected cultivation

Srinidhi G 1,2,✉, K N Agrawal 3, Sweeti Kumari 1, R R Potdar 1, N S Chandel 1, K V Ramana Rao 4, Karan Singh 5, Manoj Kumar 1
PMCID: PMC12484682  PMID: 41027980

Abstract

The agricultural operations such as digging, transplanting and weeding in protected cultivation are performed by both female and male workers. The posture adopted during these operations such as forward bending and squatting leads to the involvement of various muscle groups and leads to continuous exertion. Excessive loading and long working hours result in work related musculoskeletal disorders. Surface electromyography (sEMG) is a useful tool to measure and correlate muscle fatigue experienced by workers during these operations. In the present study,twelve workers (six female and six male) performed digging, transplanting and weeding operations using both traditional and improved tools inside a polyhouse (560 m2). The muscles selected for digging and transplanting operations were the brachioradialis (BR), biceps brachii (BB), triceps brachii (TB), anterior deltoid (AD), erector spinae longissimus (ESL) and biceps femoris (BF). For weeding, all the muscles remain the same except for the biceps femoris, which is replaced by the gastrocnemius (GC). Before the start of the experiments, the worker’s maximum voluntary contraction (MVC) values were assessed using information gathered from reviews. For female workers, with traditional tools, the percentage of muscle fatigue for the digging was (bicep femoris-58.19%, erector spinae- longissimus-53.79%, biceps brachii-31.48%), weeding was (brachioradialis-33.59%, gastrocnemius -33.35%) and transplanting was (bicep femoris-37.53%), respectively. Similarly, male workers, with traditional tools, the percentage of fatigue for the digging (bicep femoris-50.50%, erector spinae- longissimus (ESL)-49.99%, biceps brachii-31.55%), weeding (brachioradialis-28.83%, gastrocnemius-28.70%) and transplanting (bicep femoris-31.62%), respectively. Using the improved tools and machinery mini power tiller (BF:80.24%-F, 85.42%-M, ESL:75.35%-F, 79.93%-M, BB:33.83%-F, 37.50%-M), cycle hoe weeder (ESL:83.06%-F, 86.73%-M, GC:76.00%-F, 85.27%-M, BB:55.65%-F, 61.90%-M), single row vegetable transplanter (BF:90.43%-F, 93.51%-M, ESL:77.39%-F, 82.22%-M, BB:23.48%-F, 27.27%-M) results in decreased muscular load as compared to traditional tools/machinery. The data suggests that the use of improved tool and machinery can help to reduce muscle fatigue and enhance the safety and productivity of workers.

Keywords: Surface EMG, Protected cultivation, Muscle, Muscular fatigue assessment, Occupational health

Subject terms: Health care, Health occupations, Risk factors

Introduction

Work-related musculoskeletal disorders (WMSDs) are presently a topic of substantial focus in the field of occupational health. The individuals working at the agricultural farms, particularly those engaged in physically demanding farming operations, show a higher susceptibility to musculoskeletal disorders1–3. While variety of machinery and mechanization of farms have greatly reduced the need for manual labour in field preparation, inter cultivation and sowing in fields, but the utilization of said equipment remains incomplete in protected cultivation.

Protected cultivation, involves a number of operations such as preparation of soil by digging, forming, laying the mulching sheet over the bed, sowing of seed, inter-cultivation and harvesting. These operations involve repetitive movement and odd postures such as forward bending, squatting, stooping, etc1. After bed formation and laying of plastic mulch cover on the bed, transplanting of seedlings is carried out by workers. Transplanting involves placing of seedlings into the hole made on the bed. This operation involves forward bending and repetitive movements of the upper extremities. At the initial stage of crop, weed growth is prominent. These weeds grow in between plant rows. Most of the time female workers perform this operation in squatting posture. Workers often use the manual tool to remove these weeds. Force is required to pull and pluck the weeds required more energy. In protected cultivation operations are carried out in a confined space which offers challenging of high ambient conditions and leads to awkward postures. Muscle fatigue results due to insufficient supply of oxygen through the blood vessels and tissues specifically refer as local muscle fatigue. Local muscle fatigue is a state where the ability of force generation gets decreased4. The analysis of muscle fatigue is significant in the areas of clinical diagnosis, sports, biomechanics, agriculture, etc.

Muscle fatigue is assessed using both subjective and quantitative methods. The subjective method, like the rating of fatigue scale, measures perceived fatigue by considering both physical and mental factors, giving a comprehensive view of how tired a person feels5. Quantitative methods, such as isokinetic dynamometry, measurement of muscle fatigue by assessing maximum torque and total work during controlled limb movements6,7. Another approach is using biochemical markers like serum lactate, ammonia, and hypoxanthine, which provide insight into the physiological processes of muscle exhaustion4.

Surface electromyography (sEMG) is the most commonly used method to analyze dynamic muscular fatigue8–10. sEMG capture the small electrical signals developed by the ion exchange across muscle fiber called electromyograms7,11. Electrodes are placed on the skin surface to measure the muscle activity by surface EMG (sEMS). sEMS is a non-invasiveness technique with minimal involvement of risk12,13. Common sEMG parameters used to assess the activity of muscle include root mean square (RMS), mean frequency (MNF), median frequency (MDF), and muscle workload expressed as percentage maximum voluntary contraction9. The %MVC is derived by comparing the real-time RMS signal activity of muscle to the signal of the same muscle under maximal contraction without any external loads or constraints, indicating the extent of muscle fatigue during a specific task14.

In one investigation assessing muscle activity during land preparation work, the impact of hoe handle length and the angle made between the arm and shoulder on muscle engagement was evaluated. The results indicated that handle length of 800 mm and handle angle of 43° with the blade significantly reduced muscle activation in the biceps brachii and trapezius muscles compared to the traditional hoe15. Park16, reported that the biceps femoris muscle was more actively used during digging operation compared to other muscles in agriculture activities17. A study by Fathallah et al.18 found that manual weeding poses high risk of work-related musculoskeletal disorders (WMSDs) in the lower back due to prolonged static posture. The study recommended using a hoe for weeding to lower the trunk bending angle and reduce stress on the spine18. Parimalam et al.19 studied the transplanting activity that primarily engaged female workers in a forward bending position. The outcomes indicated that the utilization of the single row vegetable seedling transplanter led to a decrease in muscular exhaustion and uncomfortable postures compared to the conventional method of transplanting19. A similar study on paddy transplanting activity indicated a high risk of knee and ankle injury for farmers20. Ansari21 studied the chaff cutting operation, and reported that biceps brachii (BB) was the most fatigued muscle compared to the other muscles. Moreover, they suggested that the muscles involved in this task can help in modification of equipment to reduce fatigue and improve safety21. Keeping the above points in view. In this present study, three operations (digging, transplanting, weeding) were selected based on the discomfort data collected from the farm workers (Data not shown). In that top three operations were selected such as digging, transplanting and weeding and investigated for male and female workers. Independent parameter tools (traditional and improved tool/machinery) and dependent is muscular activity.

Methodology

Location

The protected cultivation structure selected for the study is located at the Precision Farming Development Centre (PFDC) of the Indian Council of Agricultural Research-Central Institute of Agricultural Engineering (ICAR-CIAE), Bhopal, India (Latitude: 23.311318° N, Longitude: 77.403109° E, Area of polyhouse: 560 m2).

Subjects

Twelve healthy and experienced farm workers (six female and six male) were selected. The selected subjects were within the age group of 25–40 years as indicated by previous studies22. The selected individuals did not have any chronic medical diseases or health issues. The average age of female and male subjects was 39.3 (± 5.9) and 29.6 (± 9.6) years, respectively. Their average weights were 52.7 kg (± 6.3) for females and 55.7 kg (± 8.2) for males, with average heights of 1535 mm (± 79) and 1678 mm (± 51), respectively. The corresponding average BMI values were 24.7 kg/m2 (± 2.7) for females and 19.1 kg/m2 (± 1) for males. These measurements conform to the health norms established by the World Health Organization (WHO), implying that the subjects were found suitable for the study. All subjects were instructed to utilize their dominant hand for the operations, consistent with their routine practice. Prior to conducting the experiments, both verbal and written informed consent were obtained from all subjects after explaining the study objectives, procedures, risks, and benefits, ensuring voluntary participation. All methods were carried out in accordance with relevant guidelines and regulations, adhering to ethical standards for research involving human participants. The experimental protocols were reviewed and approved by the Advisory Committee of the Indian Council of Agricultural Research – Central Institute of Agricultural Engineering (ICAR-CIAE), Bhopal. Additionally, informed consent was obtained from all subjects and their legal guardians for the publication of images in this online open-access publication.

Muscle selection

Muscle was selected based on review17–20 and by presenting videos to the physiotherapist. As per the suggestion of the physiotherapist, pilot tests were conducted on five members to finalize the muscles for different operations. Digging, transplanting and weeding operations involve flexion and extension of the upper extremities muscles which activate the brachioradialis (BR), biceps brachii (BB), triceps brachii (TB), anterior deltoid (AD), and erector spinae longissimus (ESL) and lower extremities muscles activate the gastrocnemius (GC) and biceps femoris (BF) muscle17, therefore, these muscles were selected. Workers often operate tools and machinery with both hands, with a preference for the dominant hand. The muscles of the dominant upper and lower extremities were selected for fatigue measurement. Finally, seven muscles as shown in Fig. 1 were selected for investigation. Based on the operation, muscles were separated, four hand muscles BR, BB, TB, and AD, one back and two leg muscle ESL, GC and BF. For digging and transplanting operation BR, BB, TB, AD, ESL and BF muscles were selected. Selected muscles for the weeding operation were BR, BB, TB, AD, ESL and GC. The analysis was carried on the six active muscles (BR, BB, TB, AD, ESL, GC and BF) under different operations.

Fig. 1.

Fig. 1

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Muscle selected for farm operations23.

Measurement of maximum voluntary contraction (MVC)

After the finalization of the muscles. sEMG sensors (version 10.28, copyright © Biometrics Ltd.1998–2018, London, UK)24 were placed to record the muscle activity of the selected muscles shown in Fig. 1. MVC is the peak muscle contraction that generates the highest RMS signal amplitude and serves as the reference point for signal data analysis and evaluation of muscle fatigue8,25. MVC of particular muscles was recorded in the laboratory (Ergonomic laboratory, ICAR-CIAE, Bhopal, India). Subjects were instructed to apply maximum muscle force for 5 s. This procedure was repeated for three times with 5 min rest22. After that nRMS (normalized root mean square) value was calculated (detailed explanation in data analysis section) and average was calculated for three repetitions. Averaged nRMS (normalized root mean square) values were used for further analysis. Measurement of MVC for triceps brachii (TB) muscle, workers were asked to sit in a chair with their hand resting on the table in such a way that elbow and shoulder flexion angle is approximately 120° (Fig. 2a). Subject was instructed to apply maximum force on the handgrip dynamometer22,26–28. MVC measurement for brachioradialis (BR) and biceps brachii (BB) muscle, workers were instructed to sit straight on chair and stretch out their arms at 90°, then pull the rigid belt up at maximum level as much as they can (Fig. 2b)17,29. For erector spinae—longissimus (ESL), workers were asked to lie face down in a prone position on a mat and lifting upper body. Legs are extended straight and held at ankle (Fig. 2f). Elbows were flexed at the joint, placed at the front of the fore head. Force is applied on the scapulae, worker are instructed to resist the force applied30. A fixed belt was placed around the distal end of the upper arm during MVC for the anterior deltoids (AD). Workers were asked to exert upward forces against the belt while using only their shoulder joint (Fig. 2c)31. The gastrocnemius (GC) muscle MVC was tested and workers were instructed to lie on a bed in supine position with their legs extended horizontally. A belt was tied around the foot near to toes and was fastened to the bed. Workers pushed the belt maximum with their foot (Fig. 2e)32. For the measurement MVC of biceps femoris (BF), workers were asked to sit on a chair with knee angle at 90°, feet placed on the floor. The belt is tied around the lower leg (ankle area) and fastened to a stable structure in front of the worker. Workers were instructed to pull the lower leg backward against the resistance of the belt (Fig. 2d)33.

Fig. 2.

Fig. 2

Fig. 2

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MVC measurement for selected muscles (a) Triceps brachii (TB), (b) Brachioradialis (BR) and Biceps brachii (BB), (c) Anterior deltoids (AD), (d) Biceps femoris (BF), (e) Gastrocnemius (GC), (f) Erector spinae—longissimus (ESL), arrow indicates the direction of movement.

Experimental procedure

Three operations were conducted by the workers in the polyhouse structure (27.6 oC and 60% RH). The operations followed the standard cultivation practice used in protected cultivation. Firstly, the digging operation was performed for seedbed preparation, which was followed by transplanting of seedlings and weeding, using tool 1 and tool 2. The experimental design (RBD) is illustrated in Fig. 3. Measurement of two workers was taken in a day with shift starting at 8 AM. The first worker performed the experiment while the second waited in a separate area. All sEMG data collected for a particular operation was collected during the same week. Workers were instructed to wash their dominant side upper and lower limbs with water and clean them with a dry cloth. After shaving the muscle placement area, cotton was used to apply spirit. The electrodes were attached to the selected muscles according to the guidelines of the surface sEMG from SENIAM34. Data for workers were collected (Fig. 4), and the signal range was adjusted accordingly. Cross-verification was done while recording the data to enhance signal accuracy. Muscle activity was recorded for all operations, and the data were saved in a log file after each worker’s operation. The assessment reference period for each activity consisted of 10 min for weeding and transplanting, and 5 min for digging, all of which were part of the worker’s regular operation. A 5-min rest interval was provided between each activity to allow muscular recovery20. During these breaks, the worker remained seated in the work area.

Fig. 3.

Fig. 3

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Schematic view of the experiment.

Fig. 4.

Fig. 4

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sEMG data collection for traditional and improved tools/machinery.

Data analysis

The raw EMG signals of the muscles were preprocessed using DATALOG software (version 10.28, copyright © Biometrics Ltd.1998–2018, London, UK)24. Root mean square (RMS) signals of muscle activity were estimated using a 100-ms moving window, which was employed to smooth and reduce noise by cutting off frequencies below 10 Hz and above 250 Hz16. The signal frequency (sampling rate) was maintained at 1000 Hz. The RMS amplitude was calculated (version 10.28, copyright © Biometrics Ltd.1998–2018, London, UK)24. The worker’s log file was selected in the software, and the RMS filter was applied in the filter option. The RMS value was then saved. Afterward, in Microsoft Excel, the minimum, maximum, and mean values were calculated to determine the normalized root mean square (nRMS) value. The same procedure was followed to calculate the nRMS value for the MVC data35.

graphic file with name d33e549.gif

An Analysis of Variance (ANOVA) was conducted using the General Linear Model (GLM) to evaluate the effects of tool type and muscles on the normalized Root Mean Square (nRMS) values, of muscle activity. The factors included in the model were tool, muscle, their interaction (tool × muscle), and replication. Replication was treated as a random factor to account for variability across repeated measurements and ensure consistency in the analysis. Post-hoc comparisons were performed using Tukey’s Honestly Significant Difference (HSD) test to identify statistically significant differences between the mean nRMS values for different tool and muscle combinations. Data analysis was performed using SAS statistical software (version 9.3) and results were considered significant at a 5% significance level36. The reduction percentage was calculated by taking the difference between the mean values of muscle activity for the traditional tool and the improved tool, divided by the mean value of muscle activity for the traditional tool for a particular muscle. Fatigue percentage was calculated by comparing the muscle activity (nRMS) while performing operation divided by the MVC of muscle (nRMS) measured at the laboratory multiplied by 10022.

Results and discussion

Effect of tool on muscle activity of farm worker in digging operation

The muscle groups involved in the digging operation include the BR, BB, TB, AD, ESL and BF. These muscles are crucial for the coordinated movements required in digging, involving both upper and lower extremities. Specifically, the BB is important for elbow flexion, aiding in lifting and pulling the digging tool, while the TB assists in elbow extension, helping to push the tool into the ground. The AD is essential for raising and positioning the tool, and the ESL stabilizes the spine, which is vital for maintaining posture during bending and lifting. The BF helps stabilize the lower body to maintain balance.

Figure 5 indicates that BF exhibits the highest muscular activity for female and male workers with the spade (0.324 ± 0.042 µV) and (0.295 ± 0.006 µV) compared to the mini power tiller (0.064 ± 0.0164 µV) and (0.043 ± 0.012 µV). The AD shows the lowest activity, with nRMS values of 0.04 ± 0.033 µV and 0.02 ± 0.005 µV for the mini power tiller and 0.05 ± 0.011µV and 0.04 ± 0.007 µV for the spade, respectively for female and male workers.

Fig. 5.

Fig. 5

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Muscle activity for digging operation (a) female workers (b) male workers using traditional and improved tools. Error bar indicates standard error. Means marked with the same letter are not significantly different, based on the Tukey test with a significance level of p < 0.01.

Using the traditional tool spade (Tool 1) requires more manual effort, leading to increased muscular activity, particularly in the BF, ESL and BB, reflecting the greater physical strain from lifting, pulling, and stabilizing during digging for both female and male workers. In contrast, the mini power tiller (Tool 2) is designed to reduce physical strain, resulting in generally lower muscular activity across all muscle groups. This reduction (%) is especially evident in the BF (80.24%-F, 85.42%-M), ESL (75.35%-F, 79.93%-M) and BB (33.83%-F, 37.50%-M) indicating less strain on these muscles compared to the traditional spade tool.

Table 1 shows that replication showed no significant difference, with an F-value of 1.04 and a p-value greater than 0.05, it indicates that the tool’s impact on muscle activity is consistent across repeated tests. Tool has a significant F-value of 803.70 and a p-value less than 0.0001, this indicates a highly significant difference in the impact of the tools on muscle activity. The mini power tiller and the spade affect muscle activity levels differently, with the mini power tiller generally reducing the physical strain. The F-value of 139.53 (p < 0.0001) for the muscle variable shows that different muscles are significantly affected during the digging operation, indicating that some muscles are more engaged than others depending on the tool used. The interaction between the tool and muscle variables also shows a significant F-value of 143.15 (p < 0.0001). This suggests that the effect of the tool on muscle activity depends on the specific muscle being considered, highlighting the varying physical demands of different muscles when using different tools. Similarly, for male workers F- value (p < 0.0001) is shown in Table 2

Table 1.

ANOVA analysis for the effect of tool and muscles for female workers in digging, transplanting and weeding operations.

Operations Digging Transplanting Weeding
Variables df MSS F-Value p-Value MSS F-Value p-Value MSS F-Value p-Value
Replication 5 2.52 × 10–4 1.04NS 0.4027 7.87 × 10–5 1.02NS 0.4131 1.79 × 10–4 1.31NS 0.2747
Tool 1 1.94 × 10–1 803.70**  <.0001 6.61 × 10–2 860.42**  <.0001 8.39 × 10–2 612.36**  <.0001
Muscle 5 3.38 × 10–2 139.53**  <.0001 6.67 × 10–3 86.74**  <.0001 1.45 × 10–2 105.73**  <.0001
Tool × Muscle 5 3.46 × 10–2 143.15**  <.0001 1.65 × 10–2 215.49**  <.0001 5.37 × 10–3 39.20**  <.0001
Error 55 2.42 × 10–4 7.69 × 10–5 1.37 × 10–4
Total 71
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Table 2.

ANOVA analysis for the effect of tool and muscles for male workers in digging, transplanting and weeding operations.

Operations Digging Transplanting Weeding
Variables df MSS F-Value p-Value MSS F-Value p-Value MSS F-Value p-Value
Replication 5 5.32 × 10–4 1.74NS 0.1418 9.57 × 10–5 1.46NS 0.2172 2.73 × 10–4 0.58NS 0.7174
Tool 1 1.93 × 10–1 3145.55**  <.0001 5.73 × 10–2 876.31**  <.0001 8.84 × 10–2 935.02**  <.0001
Muscle 5 3.22 × 10–2 525.14**  <.0001 7.54 × 10–3 115.31**  <.0001 5.62 × 10–2 118.97**  <.0001
Tool × Muscle 5 3.29 × 10–2 536.96**  <.0001 1.46 × 10–2 223.11**  <.0001 2.69 × 10–2 57.08**  <.0001
Error 55 6.13 × 10–5 6.54 × 10–5 9.46 × 10–5
Total 71
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**Significant at 1% level.

NS, not significant.

MSS, mean sum of square.

The Fig. 6 indicates that muscle fatigue (in percentage) during digging operation using a mini power tiller versus a spade. According to Nag and Chatterjee (1981), a safe range for constant muscle loading in agricultural operations is between 20 and 30% of MVC37. The fatigue levels exceed this acceptable range, especially with the spade such as BF (F-58.19%, M-50.50%), ESL (F-53.79%, M-49.99%) and BB (F-36.61%, M-31.55%). The repetitive nature of the digging operation, along with the high physical demands, can lead to strain in the biceps femoris (BF), erector spinae longissimus (ESL), and biceps brachii (BB) muscles, contributing to long-term issues. Earlier fatigue in the BF muscle without proper rest and repetition exposure may result in knee-related problems due to hamstring tightness affecting joint mechanics38,39. Similarly, fatigue in the ESL can lead to low back pain40,41, while fatigue in the BB indicates repetitive elbow flexion and extension, which may cause overuse injuries in the shoulder and elbow, such as tendinitis or epicondylitis (tennis elbow)42,43. This suggests that muscle fatigue in these cases could be reaching levels where blood flow is severely restricted, as noted by Mortimer et al.44. This restriction likely occurs because the contraction strength surpasses 30% MVC, leading to local muscle fatigue under hypoxic conditions (oxygen deprivation). The mini power tiller shows lower fatigue levels compared to the spade, particularly in muscles like BF, ESL, BB, BR and AD, respectively. This suggests that using mechanized tools reduces the overall muscle load, keeping muscle contractions closer to the sustainable MVC range, thereby reducing fatigue.

Fig. 6.

Fig. 6

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Muscle load for digging operation (a) female workers (b) male workers using traditional and improved tools.

Effect of tool on muscle activity of farm worker in transplanting operation

The muscle groups involved in the transplanting operation include the BR, BB, TB, AD, ESL, and BF. The operation engages both upper and lower extremity muscles, necessitating coordinated movements throughout the body. The BR facilitates wrist movement, aiding in gripping and handling the seedlings as they are positioned in the soil. The TB assists in elbow extension, allowing the arm to stretch forward to place the seedling into the ground. The BB muscles are crucial for generating the force needed to control the tool and carefully maneuver the seedling into the soil. The AD associated with shoulder joint, it helps for lifting and positioning the seedling, while the ESL ensures spinal stability to maintain posture during the forward bending movement required to reach the ground. Additionally, the BF helps stabilize the lower body, allowing for proper balance and support during the bent-forward posture, essential for precise seedling placement.

From Fig. 7 indicates that BF exhibits the highest muscular activity for both female and male workers with the manual transplanting (Tool1) (0.209 ± 0.008 µV, mean ± standard error) and (0.185 ± 0.018 µV) compared to the single row vegetable transplanter (Tool2) (0.020 ± 0.010 µV) and (0.012 ± 0.004 µV). The AD shows the lowest activity, with nRMS values of 0.061 ± 0.0 µV (F) and 0.044 ± 0.006 µV (M) for the manual transplanting. In the case of single row vegetable transplanter, BF is lowest activated muscle with nRMS value of 0.020 ± 0.010 µV and 0.020 ± 0.010 µV, respectively.

Fig. 7.

Fig. 7

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Muscle activity for transplanting operation (a) female workers (b) male workers using traditional and improved tools. Error bar indicates standard error. Means marked with the same letter are not significantly different, based on the Tukey test with a significance level of p < 0.01.

Using the traditional tool hand hoe requires more manual effort, leading to increased muscular activity, particularly in the BF, ESL and BB, reflecting the greater physical strain by forward bend position, placing the seedling in the proper location, requires significant strength during transplanting for female and male workers. In contrast, the single row vegetable transplanter is designed to reduce physical strain, resulting in generally lower muscular activity across all muscle groups. This reduction is especially evident in the BF (90.43%-F, 93.51%-M), ESL (77.39%-F, 82.22%-M) and BB (23.48%-F, 27.27%-M) indicating less strain on these muscles compared to the traditional tool.

Table 1shows that replication showed no significant difference, with an F-value of 1.02 and a p-value greater than 0.05, it indicates that the tool’s impact on muscle activity is consistent across repeated tests. Tool has a significant F-value of 860.42 and a p-value less than 0.0001, this indicates a highly significant difference in the impact of the tools on muscle activity. The single row vegetable transplanter and the manual transplanting (hand hoe) affect muscle activity levels differently, with the single row vegetable transplanter generally reducing the physical strain19,45. The F-value of 86.74 (p < 0.0001) for the muscle variable shows that different muscles are significantly affected during the transplanting operation, indicating that some muscles are more engaged than others depending on the tool used. The interaction between the tool and muscle variables also shows a significant F-value of 215.49 (p < 0.0001). This suggests that the effect of the tool on muscle activity depends on the specific muscle being considered, highlighting the varying physical demands of different muscles when using different tools. Similarly, for male workers F- value (p < 0.0001) is shown in Table 2.

The Fig. 8 indicates that muscle fatigue (in percentage) during transplanting operation using a single row vegetable transplanter versus a manual transplanting (hand hoe). The fatigue levels exceed this acceptable range, especially with the manual transplanting (hand hoe) such as BF (F-37.53%, M-31.62%)37. The BF (hamstring tightness) muscle gets more fatigue during transplanting operation due to forward bending posture creating stress on this muscle39,46. For maintaining posture and stability, particularly during operation. For male workers, muscle activity of hand hoe is within acceptable range. The hand hoe results in higher fatigue levels for female workers, male workers generally have lower fatigue than the female. Male generally have greater muscle mass and physical strength than female, which might explain the lower fatigue levels experienced by male workers. The fatigue levels for single row vegetable transplanter most muscles (BR, BB, TB, AD, ESL and BF) are generally within or close to the acceptable range of 20–30%. The highest fatigue level is observed in the BR (20.99%), which is still within the acceptable range. Other body regions like BB, TB, AD, and ESL show even lower fatigue percentages. Ergonomic design tools reduce the overall muscle load, keeping muscle contractions closer to the sustainable MVC range, thereby reducing fatigue.

Fig. 8.

Fig. 8

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Muscle load for transplanting operation (a) female workers (b) male workers using traditional and improved tools.

Effect of tool on muscle activity of farm worker in weeding operation

The muscle groups involved in the weeding operation include the BR, BB, TB, AD, ESL and GC. Both upper and lower extremity muscles are engaged in weeding, which requires coordinated movements. A BR facilitates wrist movement, assisting in holding the tool, grabbing, and pulling weeds, while a TB facilitates elbow extension, pushing the tool into the soil. By performing repetitive actions like gripping and drawing the tool back to remove weeds, the BB muscles generate the force needed to control and maneuver the tool. An AD is essential for lifting and positioning the tool during an operation, while the ESL provides spinal stability for posture maintenance during repetitive movement and lifting. The GC muscle, located in the calf, is critical for maintaining posture and stability, particularly during activities that require squatting posture.

From Fig. 9 shows that BR exhibits the highest muscular activity for females and males with the hand hoe (Tool 1) (0.185 ± 0.008 µV, mean ± standard error) and (0.170 ± 0.018 µV) compared to the cycle hoe weeder (Tool 2) (0.134 ± 0.006 µV) and (0.112 ± 0.007 µV). The TB shows the lowest activity, with nRMS values of 0.078 ± 0.016 µV (F) and 0.075 ± 0.006 µV (M) for the hand hoe. In the case of cycle hoe weeder, ESL is lowest activated muscle with nRMS value of 0.022 ± 0.010 µV and 0.015 ± 0.004 µV, respectively.

Fig. 9.

Fig. 9

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Muscle activity for weeding operation (a) female workers (b) male workers using traditional and improved tools. Error bar indicates standard error. Means marked with the same letter are not significantly different, based on the Tukey test with a significance level of p < 0.01.

Using the traditional tool hand hoe requires more manual effort, leading to increased muscular activity, particularly in the BR, GC and AD, reflecting the greater physical strain for stretching out the hand, grabbing, and pulling weeds require significant strength during weeding for female and male workers. In contrast, the cycle hoe weeder is designed to reduce physical strain, resulting in generally lower muscular activity across all muscle groups18. This reduction is especially evident in the ESL (83.06%-F, 86.73%-M), GC (76.00%-F, 85.27%-M) and BB (55.65%-F, 61.90%-M) indicating less strain on these muscles compared to the traditional hand hoe tool.

Table 1 shows that replication showed no significant difference, with an F-value of 1.31 and a p-value greater than 0.05, which indicates that the tool’s impact on muscle activity is consistent across repeated tests. Tool has a significant F-value of 612.36 and a p-value less than 0.0001, this indicates a highly significant difference in the impact of the tools on muscle activity. The cycle hoe weeder and the hand hoe affect muscle activity levels differently, with the cycle hoe weeder generally reducing the physical strain. The F-value of 105.73 (p < 0.0001) for the muscle variable shows that different muscles are significantly affected during the weeding operation, indicating that some muscles are more engaged than others depending on the tool used. The interaction between the tool and muscle variables also shows a significant F-value of 39.20 (p < 0.0001). This suggests that the effect of the tool on muscle activity depends on the specific muscle being considered, highlighting the varying physical demands of different muscles when using different tools. Similarly, for male workers F- value (p < 0.0001) is shown in Table 2.

The Fig. 10 indicates that muscle fatigue (in percentage) during weeding operation using a cycle hoe weeder versus a hand hoe. The fatigue levels exceed this acceptable range, especially with the hand hoe such as BR (F-33.59%) and GC (F-33.35%)37,45. BR fatigue can lead to lateral epicondylitis (tennis elbow), characterized by pain and inflammation in the elbow due to repetitive strain. This fatigue may also contribute to forearm muscle strain and tendinitis, affecting grip strength and hand function. Fatigue in the GC may result in calf muscle strain or tendinitis in the Achilles tendon47. Prolonged fatigue in this muscle can also contribute to plantar fasciitis, where the heel and arch of the foot are affected due to improper foot mechanics and overexertion. For male workers, muscle activity of hand hoe is within acceptable range. The hand hoe results in higher fatigue levels for female workers, male workers generally have lower fatigue than the female. Male generally have greater muscle mass and physical strength than female, which might explain the lower fatigue levels experienced by male workers. The fatigue levels for cycle hoe weeder most muscles (BR, BB, TB, AD, ESL, and GC) are generally within or close to the acceptable range of 20–30%. The highest fatigue level is observed in the BR (24.31%), which is still within the acceptable range. Other body regions like BB, TB, AD, and ESL show even lower fatigue percentages. This suggests that using ergonomical design tools reduces the overall muscle load, keeping muscle contractions closer to the sustainable MVC range, thereby reducing fatigue.

Fig. 10.

Fig. 10

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Muscle load for weeding operation (a) female workers (b) male workers using traditional and improved tools.

Comparison of farm operation in protected cultivation

In protected cultivation, both female and male workers experience severe fatigue during the digging operation, especially when compared to transplanting and weeding. In transplanting, the lower leg muscles are affected in both genders, leading to fatigue. However, during weeding, only female workers exhibit fatigue in the brachioradialis (BR) and gastrocnemius (GC) muscles. For female workers, hand muscles also experience fatigue during digging and weeding, which is associated with pain in the shoulder and elbow. These findings indicate that pain in the knees and lower back is common for farm workers using traditional tools. Numerous studies based on subjective assessments have indicated that farm workers commonly suffer from musculoskeletal disorders (MSDs) related to the knee, lower back, elbow, and shoulder48–52. The quantitative data from this study further confirm these findings. In comparison, female workers experience more fatigue than males. One contributing factor is that males tend to be physically stronger, which allows them to handle physical labor more effectively. Additionally, female workers often engage in household chores in the morning before coming to work, leaving their muscles insufficient time to rest. This lack of rest may contribute to higher levels of fatigue in female workers than in males.

Limitation

This study has some limitations. Comparing similar farming activities in an open field versus within a protected structure could provide valuable insights into differences in muscle activity and fatigue under these conditions. Additionally, the sample size in this study is relatively small and could be increased for more robust results. Furthermore, conducting the study at different temperatures inside the protected structure could help assess the effects of temperature and humidity on muscle activity.

Conclusion

The study indicates that traditional tools used in agricultural operations such as digging, weeding, and transplanting result in significant muscle activity and fatigue, which can lead to musculoskeletal disorders (MSDs) such as lower back pain, hamstring stiffness, tendinitis, and lateral epicondylitis. For female workers, muscle fatigue was particularly high in the biceps femoris (BF), erector spinae longissimus (ESL), and biceps brachii (BB) during digging, while male workers exhibited similar fatigue pattern. In transplanting, both female and male workers experienced fatigue in the BF muscle. Weeding caused notable muscular strain, particularly in the brachioradialis (BR) and gastrocnemius (GC) muscles for female workers, whereas only the gastrocnemius muscle showed fatigue in male workers. However, the use of improved tools and machinery, such as the mini power tiller, cycle hoe weeder, and single row vegetable transplanter, significantly reduced muscle activity and fatigue across all operations. The results strongly suggest that adopting ergonomic tools and machinery can mitigate fatigue, prevent injuries, and enhance worker safety and productivity. To optimize these benefits, it is crucial to develop gender-specific designs and promote worker acceptance of ergonomic tools and machinery in agricultural practices.

Acknowledgements

Thank you to the director ICAR-CIAE, Bhopal for the providing necessary resources for conducting the research work.

Author contributions

Conceptualization—Srinidhi G, K.N. Agrawal, Data collection, Analysis and Writing original draft preparation – Srinidhi G, Review and editing – K.N. Agrawal, R.R. Podtar, Sweeti Kumari, Karan Singh, N.S. Chandel, K.V.R. Rao, Statistical analysis—Manoj Kumar, Project administration—K.N. Agrawal.

Funding

None.

Data availability

The author confirm that the data supporting for the study are provided within the article.

Confict of interest

No potential conflict of interest was reported by the authors.

Ethics approval

The majority of farm workers are illiterate. However, they were provided with comprehensive explanations about the study, and verbal consent obtained from the subjects. Importantly, No treatment or interference was done into his or her regular work routines; only observation was recorded.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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