Physiological responses during and after intermittent sorting of postal parcels

Abstract

Physiological responses including ventilatory gas exchange, blood lactate (LA) and heart rate (HR) were studied during and after intermittent manual sorting of postal parcels in a simulated workplace constructed in the laboratory. Responses to parcel sorting were compared to those obtained during arm crank and cycle exercise. The subjects were 21 healthy male sorters. Their age was 33 ±6 years and weight 78·3 ±12·7 kg. The subjects' maximal oxygen consumption ([Vdot]O2 max) was 2·52±0·32 Imin−1 for arm cranking, and 3·24+0·441min−1 for cycling. The subjects sorted parcels with a mean weight of 51 kg from a container onto two trollies for 3·5 min at each of the following work rates; slow (3 ± 0 parcels min−1), habitual (8·6±2·4 parcels min−1), accelerated (10·8 ± 3middot;1 parcels min−1), and maximal (16·9 ±7·6 parcels min−1). The tasks were separated by rest periods of 30 s for venous blood sampling, and the recovery was followed for 16 min. At the habitual work rate, [Vdot]O2 was 1·36±0·381min−1, LA 1·8±0·9mmol−1, and HR 105 ± 22 beats min−1. The parcel sorting studied was predominantly aerobic (LA<4·0mmol l−1) up to the work rate of about 20parcelsmin−1. After the recovery period, breathing frequency and HR remained significantly higher than at rest. The physiological responses to parcel sorting substantially differed from those to arm cranking, whereas they were almost equal to cycling.