The physical workload involved in parcel handling

Abstract

Sixteen male subjects of varying age and anthropometric characteristics were each asked to perform a seriesof parcelhandlingactivitiesat an 'habitual' ratefor 2 h. Work rate and oxygen consumption were monitored for the various task components which werearranged to enable carryover effects to be investigated. The results indicated that an energy output of between 400 Wand 500 W could be considered as being 'habitual' for this form of iask. However in submaximal tasks of this nature anthropometric factors are likely [0 playa greater part in determiningenergy expenditure than age or work rate factors as work rate is largelyinfluenced by the interaction between anthropometric characteristics and workplace design. I. IntroductionSince the work of Taylor in 1913,job evaluation and design issues have been based on scientific estimates of physical work load.In practice these estimates are derived from analyses of the physicalcharacteristics of the task, time studies of experienced workers and subjective ratings of effort. The estimates may be supported by evidence from work physiology, laboratory studies involving a variety of methods of controlling physical work output (treadmills etc.) and a variety of physiological indices based on heart rate, respiratory function and biochemical analyses (Crowden 1932, Astrand and Rodahl 1977).The bridge between the laboratory and practice is associated with conflicting problems of reliability and validity. However an increasing number of bridging studies are being reported which make use of sophisticated equipment and statistical design facilities and which can achieve credibility by both researchers and practitioners. Snook (1978) reported the results of extensive psychophysical studies for estimating acceptable weights and forces in materials handling using task durations ofabout 4·5 h. Heart rate methods were used by Rodahl and Vokac(1977) for the study of the habitual work stress to trawlermen. Because of the inherent variability of the work performed by trawlermen a wide range in heart rates was observed but mean rates of just over 100 beats min -1 were found for deckhands during their working period. Htay (1978) also used heart rate methods to observe the habitual physical activities of rural Burmese women. These authors used a diary method of estimating the proportions of time spent on different activities at different times of the year and then sampled heart rates for particular activities. During certain periods of the year it was implied that mean heart rates of 130 beats min-1 were maintained for long periods during the activity of 'pounding glutinous paddy seeds'.The stability advantages of oxygen uptake methods were preferred by Haisman et al. (1972) in a study of handcart pushing. In this study work periods ofJO min were used and energy expenditure values of about 510 W were observed for both treadmill and outdoor circuits. Similar methods were used by Datta et al. (1978) in a study of rickshaw pulling with similar energy expenditure results. However Nag et al. (19...

Physiological responses during and after intermittent sorting of postal parcels

“…unpublished results). The present results also agree with those reported by Peacock (1980) in parcel-handling tasks.…”

“…As an example, in the laboratory and during actual manual sorting, the habitual work rates were almost equal (8.6 f 2.4 vs. 7-3 f 2.6 parcels min-I; Louhevaara et al unpublished results). In the experiments of Peacock (1980), the mean individual habitual work pace for loading of postal parcels was lower, being about four parcels min-I.…”

“…The lifting tasks were predominantly aerobic up to 3 5 4 0 % of the maximal I/O, for lifting, when the b'0, was from 1.0 to 1.51min-' depending on the weight of the box. Peacock (1980) studied VO, in various parcel-handling tasks. The mean weight of the parcels was 5.6 kg (range 0-9-9-5 kg), and for the entire work period of 2 hours, work was carried out at a habitual rate.…”

“…Previous studies on aerobic and anaerobic responses to manual material handling have mainly focused on lifting tasks, and the responses were compared with various techniques and frequencies of lifting, and weights of load (Snook 1978, Petrofsky and Lind 1978a, Garg and Saxena 1979, Peacock 1980). In the experiments of Petrofsky and Lind (1978a, b), boxes weighing 0.9, 6.8, 22-7 and 36.4 kg were lifted up to or down from a height of 60cm.…”