Ergonomic Assessment of Postural Effect on Work-Related Musculoskeletal Risks and Evaluation of Grip Strength and Back Muscle Fatigue with Electromyography among the Pearl Millet Workers (Farmers) of Agra

Abstract

Background: Pearl millet (Pennisetum glaucum) cultivation involves physically demanding manual work that may expose agricultural workers to musculoskeletal strain and muscle fatigue. Repetitive movements and sustained physical exertion may particularly affect workers engaged in manual harvesting. However, limited evidence is available regarding the combined musculoskeletal burden, electromyographic muscle fatigue, and handgrip strength of pearl millet farmers. Objective: The present study aimed to assess and compare work-related musculoskeletal disorder (WMSD) , electromyographic indicators of muscle fatigue, and handgrip strength among pearl millet farmers and non-agricultural workers. Methods: A comparative cross-sectional study was conducted among 20 male participants from Madhanpur village, Agra district, Uttar Pradesh, comprising 10 pearl millet farmers and 10 non- agricultural workers. Participants were selected through purposive sampling. Musculoskeletal symptoms were assessed using the Modified Nordic Musculoskeletal Questionnaire, and the total number of affected body regions was used to determine individual Work-related Musculoskeletal Disorder(WMSD) Muscle fatigue was assessed using surface electromyography (sEMG) of the bilateral erector spinae and external oblique muscles. Handgrip strength was measured separately for the right and left hands using a handgrip dynamometer, with the mean of three trials used for analysis. WMSD burden was compared using the Mann–Whitney U test, while MPF decline and handgrip strength were compared using Welch\'s independent-samples t-test. Results: Pearl millet farmers demonstrated a significantly greater WMSD burden than non- agricultural workers (6.80 ± 1.32 vs. 1.90 ± 1.20; U = 100.00, p < .001). Low-back symptoms were most frequently reported among farmers (100%), followed by upper back symptoms (80% each). Farmers also demonstrated significantly greater MPF decline across the left and right erector spinae and external oblique muscles (p < .001 for all comparisons), with very large effect sizes. In contrast, handgrip strength was significantly greater among farmers in both the right hand (8.80 ± 2.39 vs. 4.85 ± 1.65 kg; p = .00056) and left hand (6.58 ± 0.88 vs. 4.66 ± 0.17 kg; p = .000057). Conclusion: Pearl millet farmers experienced more work-related musculoskeletal problems and greater muscle fatigue than non-agricultural workers, even though they had stronger handgrip strength in both hands. This shows that having stronger hands does not always mean having fewer musculoskeletal problems or less muscle fatigue in the body. The study suggests that pearl millet farmers need proper ergonomic education, safer working methods, better harvesting techniques, and preventive measures to reduce the risk of work-related musculoskeletal problems.

Introduction

This study examines the work-related musculoskeletal disorders (WMSDs), muscle fatigue, and handgrip strength of pearl millet (bajra) farmers compared with non-agricultural workers.

• Background: Pearl millet harvesting involves repetitive cutting, bending, lifting, and prolonged awkward postures. These activities can place considerable stress on the back, shoulders, arms, and legs and may cause musculoskeletal discomfort and muscle fatigue.
• Objective: The study aimed to assess occupational musculoskeletal problems using the Modified Nordic Musculoskeletal Questionnaire, muscle fatigue using surface electromyography (sEMG) and Mean Power Frequency (MPF), and muscular capacity using a handgrip dynamometer.
• Participants: The study compared 10 male pearl millet farmers with 10 non-agricultural workers. The groups were broadly similar in age, height, weight, and BMI. Farmers had an average work experience of about 12.7 years.
• Procedure: Farmers performed pearl millet harvesting activities continuously for 20 minutes, involving bending, cutting, and lifting. Muscle activity was monitored in the left and right erector spinae and external oblique muscles.
• Musculoskeletal disorders: Farmers reported substantially more affected body regions than non-farmers. Their average WMSD burden score was 6.80, compared with 1.90 for non-farmers (p < .001).
• Most affected body regions: Among farmers, the lower back was most commonly affected, with 100% reporting symptoms. Upper back and knee problems were reported by 80%, while shoulder and elbow symptoms affected 70%.
• Muscle fatigue: Farmers showed significantly greater MPF declines in all four monitored muscles, indicating substantially greater muscle fatigue:
  • Left erector spinae: −25.84 Hz vs. −6.50 Hz
  • Right erector spinae: −9.20 Hz vs. −3.20 Hz
  • Left external oblique: −22.50 Hz vs. −5.00 Hz
  • Right external oblique: −23.80 Hz vs. −6.00 Hz
    All differences were statistically significant (p < .001).
• Handgrip strength: Interestingly, farmers had greater handgrip strength than non-agricultural workers. Right-hand strength was 8.80 kg vs. 4.85 kg, while left-hand strength was 6.58 kg vs. 4.66 kg. Both differences were statistically significant.
• Interpretation: The results suggest that long-term agricultural work may improve functional hand strength through occupational adaptation, but this does not protect farmers from musculoskeletal problems or trunk-muscle fatigue.
• Overall conclusion: Pearl millet harvesting places substantial ergonomic and physiological demands on workers. Farmers experience significantly higher WMSD burden and muscle fatigue despite having stronger handgrip strength. The findings highlight the need for ergonomic interventions, improved harvesting tools, posture management, work-rest schedules, and fatigue-reduction strategies in pearl millet cultivation.

Conclusion

The sEMG findings further demonstrated significantly greater MPF decline among farmers across the left and right erector spinae and external oblique muscles. The very large effect sizes observed across all four muscles indicate substantial differences in fatigue-related electromyographic changes between the occupational groups. Therefore, indicating that electromyographic muscle fatigue, as reflected by MPF decline, differed significantly between pearl millet farmers and non-agricultural workers. At the same time, farmers demonstrated significantly greater handgrip strength in both hands than non-agricultural workers. This suggests that greater occupationally associated handgrip capacity does not necessarily protect workers from broader musculoskeletal burden or trunk-muscle fatigue. Therefore, this indicating a statistically significant difference in handgrip strength between pearl millet farmers and non-agricultural workers, with farmers demonstrating greater grip strength in both hands. It is possible that the occurrence of MSD among agricultural workers is related to the workers\' posture, the length of time spent at work, and the tools they use. It was low back pain that was the main issue when performing the various bajra cultivation tasks. It was a major contributor to sickness and absenteeism. Occupational hazards can permanently alter discs, apophyses, ligaments, and other structures of the musculoskeletal system. Due to poor economic condition the workers were deprived of proper nutrition and could not avail suitable treatment for different health problems. Thus, musculoskeletal disorders became intensified. The following may be helpful for reducing the low back pain and problems of dust particles: 1) Low back pain and upper leg disorder might be reduced primarily by maintain proper work-rest scheduled during performing different bajra cultivation tasks. 2) Relief from low back pain can be obtained by lying in the supine position, grasping the knees and then squeezing the thighs against the chest for about five seconds and obtained other types of exercise. 3) The conservative treatment of low back pain ultimately rests and proper education. 4) Acute-severe low back pain problems respond to bed rest. 5) For avoiding the dust particles they should use low-cost musk and sunglass during performing threshing jobs. As an alternative workers may use cloth piece covering the nose and mouth. 6) Awareness program for educating the workers regarding ill effects of adopting awkward work posture.

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Copyright

Copyright © 2026 Saurabh Satsangi, Anami Saran. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.