Tractor controls actuating force limits for Indian operators

In four-wheel tractors, proper design of controls is important for comfortable and safe operation of the tractor. The design involves location and dimensions of controls as well as strength limits for operating these controls. The present study was aimed to quantify human strength for operation of tractor controls and to recommend the maximum control actuating forces for normal operation of tractors based on strength capability of 3,423 Indian male agricultural workers. The 5th percentile values of strength parameters i.e. leg strength sitting (left and right), foot strength sitting (right), torque strength (both hands) sitting, push strength (left hand and right hand) sitting and pull strength (left hand and right hand) sitting of agricultural workers collected using a strength measurement set-up were taken into consideration for the study. It was recommended that the maximum actuating forces for normal operation of frequently operated brake and clutch pedals of tractors should not exceed 260 N and 125 N based on 5th percentile values of right and left leg strength of male agricultural workers, respectively. The maximum actuating force required in steering wheel operation should not exceed 51 N based on 5th percentile value of torque strength (both hands) sitting of workers. The maximum actuating forces required for operating frequently operated levers viz. gear selection, speed selection, hydraulic control and hand throttle of Indian tractors should not exceed 46 N, 46 N, 25 N and 25 N, respectively. It may be concluded that the maximum actuating force limits as given in Bureau of Indian Standards IS 10703 are very high as compared to the findings of the study based on strength data of Indian male operators, which highlight the need to revise the standard.

Agricultural injuries in Central India: nature, magnitude, and economic impact

A study was carried out in Madhya Pradesh (Central India) to collect data on injury-causing agricultural incidents during the period 1995-1999. The overall incidence rate was 1.25/1000 workers/year. About 9.2% of the incidents were fatal, and most of the fatal incidents were due to tractors and snakebites (42.9% each). About 77.6% of all incidents were due to farm machinery, 11.8% were due to hand tools, and the remaining 10.6% were due to other sources like snakes, wells, etc. Data on 1,911 incidents reported in 10 leading newspapers published during the five-year period (1995-1999) from different regions of the state were also collected and analyzed, which indicated that only major or roadside agricultural incidents were reported in newspapers. Based on the survey data, it was estimated that in the year 2000 there would have been about 17,480 agricultural incidents in Madhya Pradesh, causing death to about 2,050 workers and injuries to about 16,770 workers, including amputations of limbs, burns, cuts, etc. Total monetary loss due to agricultural injuries in the state of Madhya Pradesh has been estimated as US $27 million/year.

Longitudinal studies of the duplication form of Charcot-Marie-Tooth polyneuropathy

This study presents a longitudinal comparison of motor nerve conduction velocities (MCVs) in patients with Charcot-Marie-Tooth type 1A with proven duplication of a segment of chromosome 17p11.2p12. Results were compared for 8 CMT1A duplication patients from one family whose MCV measurements were taken 22 years apart (1967 and 1989). Measurements from a total of seven median motor and five peroneal motor MCVs were compared. Median MCVs showed a slight reduction that averaged 2.2 m/s, and peroneal MCVs showed an average decrease of 3.0 m/s. In addition, mild objective increase in limb weakness was seen in only 1 of 8 patients and subjective symptoms of gradual worsening of leg strength were noted in half the patients over the same period. In this study of a small group of CMT1A patients with proven segmental duplication of chromosome 17p11.2p12, the motor conduction velocities and clinical motor exam did not change significantly over 22 years.