Ergonomics in the hoeing operation

The hoeing operation is extensively required in farm tasks, such as seed-bed preparations, cutting root crops, etc. In seven male farmers (age: 27.4 ± 5.9 years), using two types of hoes (A&B), the physiological and biomechanical strains were evaluated, and hoeing speeds in low lift (LL) and high lift (HL) work were optimized. The heart rates (161–176 beats/min) and VO₂ demands (71–89% VO_2max) indicated extremely heavy work loads. Hoe A (blade-handle angle: 65°) was less strenuous in LL, while Hoe B (blade-handle angle: 87°) was better in HL work. During the hoeing sequence, the torque and compressive forces at the L5-S1 disc increased with the trunk inclination, up to about 65°; beyond 55° inclination, the torque at the L5-S1 disc exceeded the upper limit (135 Nm) allowed for a day's work. The work output was optimized equating at 50% VO_2max, i.e, stroke rate: 53 and 21 strokes/min; weight of soil dug: 123 and 54 kg/min, and area of soil dug: 1.34 and 0.33 sq.m./min in LL and HL work respectively. In general, farmers are suggested to adopt the LL mode of hoeing; with a 10 min work to 7 min rest ratio, the 8 h work output was derived as 400 to 450 sq.m. A hoe, weighing about 2 kg, having blade-handle angle 65 to 70°, blade length 25 to 30 cm, blade width 22 to 24 cm, handle length 70 to 75 cm, and the handle diameter 3 to 4 cm may be suitable for different modes of hoeing.