[Applied physiology: the work of driving an industrial heavy-duty truck on the highway].
Scope of this work was the investigation of the following parameters: energetic metabolism, by O2 consumption measurement using the open-circuit technique; pulmonary ventilation; cardio-circulatory activity behaviour, by recording heart rate, E.C.G., arterial blood pressure and plethysmography of lower limbs; body temperature pattern; visual function, through the determination of the visual field; kidney function through urine analysis; body joints flexibility, by proper test. The subjects chosen for this investigation are three experienced heavy-duty vehicle drivers that where submitted to proper checks before, during and after having driven a 190.38 Model truck fitted with spoiler and an S.R. Viber, high cargo body tarpaulin, PTT, 43.2 tons overall weight truck, over 9 different courses including town traffic, level highway, up and downhill highway with different gradients, in a period from 9 a.m. to 8 p.m. Along the total run of 404 kilometres, covered in 364 minutes, recording of the parameters under investigation was carried out over 249 kilometres covered 240 minutes (72% of overall driving time). Energy expenditure (1.20 +/- .19 Kcal/min at rest) resulted higher on steep uphill stretches with many bends (2.28 +/- .44 Kcal/min) than on less steep up- and downhill stretches and in city traffic (1.82 +/- .21 Kcal/min). The lowest energy expenditure--in some cases lower than the value found in the experimental rest--was recorded during motorway driving (1.28 +/- .19 Kcal/min). Pulmonary ventilation was characterized by frequent changes in rate and tidal air, in strict relationship with driving work bio-mechanical requirements (operation of the steering wheel). Also heart rate underwent ariations well in line with the energy expenditure pattern: of limited magnitude in uphill driving (+33% max over the value at rest), up to values identical with those at rest in the level highway drive. No appreciable variations were recorded in the respiratory quotient, calories/ventilation ratio and oxygen pulse. No significant changes occurred in arterial blood pressure, body temperature, auditory, visual and kidney functions, and in flexibility. Conversely, slight swelling (5%) of lower limbs was noticed at the end of the driving day. It was hence proven that--from the standpoint of energy expenditure--the work performed in driving a vehicle is not too exacting and does not induce particularly high nervous stresses. However, under given conditions, such as steady speed driving in level highway, a pre-sleep state occurs in all cases approximately after the first 30 minutes of driving, which in most cases the driver is not even aware of.(ABSTRACT TRUNCATED AT 400 WORDS)