Effects of load, speed and gradient on physiological responses of rice mill workers in load carrying

BackgroundBags of paddy, rice, bran, and rice husk are carried by rice mill workers on their back or head.ObjectiveThis study evaluated the effects of load, walking speed, and gradient on the physiological responses of rice mill workers carrying load on the back and head to recommend load limits and maximum allowable work times (MAWT) for these workers.MethodsHeart rate (HR) and Oxygen uptake (VO₂) were measured on 12 males rice mill workers. Load was carried on the back and head, at three different loads of 40%, 50%, and 60% of body mass (BM), two walking speeds of 0.62 and 0.89 m/s, and two gradients of 0° and 5°. The recommended load to be carried by a worker was estimated based on 35% and 45% of VO_2max for a work shift of 8-h and 4-h, respectively. The MAWT was estimated using physiological demand in %VO_2max.ResultsThe HR and VO₂ responses were 2.4% and 4.5% higher during load carrying on head than those on the back, respectively. At 35% and 45% of VO_2max, the recommended load varied from 0% to 52.6% and 39.3% to 74% BM, respectively, for different experimental conditions, with MAWT varying from 2.67 to 11.32 h.ConclusionsThese findings contribute to the development of evidence-based guidelines for optimal load limits in rice mills, aimed at improving worker safety and comfort. Given the high physical demands in this sector, there is an urgent need to establish standardized load-carrying capacity recommendations for Indian workers.