Aerobic power and muscle strength among young and elderly workers with and without physically demanding work tasks
Introduction
Aerobic power and muscle strength normally decrease with age. However, training of the specific capacities is known to counteract this decrease. Efficient aerobic and strength training are characterised by high demands on the specific capacity to be improved. (i.e. aerobic training should pose a high strain on the circulatory system and strength training should be performed with near maximal force in the involved muscle groups). Speculations have therefore been made on a possible training effect in jobs with a high physical demand in relation to the workers’ capacity. On the other hand, it has been found that performing physically heavy work may have a deteriorating effect on aerobic power and muscle force (Nygård et al., 1994). Waste collection is an example of a physically heavy work with high demands on aerobic power and muscle force (Laursen and Schibye, 2000; Schibye et al., 1997; Schibye and Christensen, 1997; Schibye and van Lelieveld, 1995). In the present study, the physical capacity was compared for elderly and young waste collectors and for elderly and young workers in jobs without physically heavy demands.
The aim was to investigate if waste collection has a training or a wearing effect on the workers’ physical capacity, and to discuss indications of selection of the young workers with the highest physical capacity.
Section snippets
Subjects
The study included 19 young male waste collectors with a mean (range) age of 25 (19–32) years and seniority below two years, and 28 elderly male waste collectors with a mean age of 54 (47–64) years and seniority above 20 years. Age-matched control groups without physically heavy work were made from the Survey of Work and Health in Danish Employees (Borg and Burr, 1997) from a subsample of 467 employees (231 females and 234 males) on whom similar physiological measurements were performed (
Results
The Manova test showed that both the type of work and the age of the worker have a significant influence on the worker's physical capacity, and as a whole, the highest capacities were found among the young waste collectors. All results for the four subgroups are listed in Table 1, Table 2. Regarding the leisure time activity, no difference was found among the four groups.
Maximal aerobic power
In agreement with the results from many other studies, we find that the aerobic power is lowest in the elderly age groups (De zwart et al., 1995; Era et al., 1997; Ilmarinen, 1992; Nygård et al., 1994; Suurnäkki et al., 1991; Åstrand, 1960). In a review based on 20 studies concerning the workload and the ageing worker, De zwart, found a decrease of 7–10% during a 10-year period (De zwart et al., 1995). The decrease in aerobic power in our study is approx. 1% per year and independent of job
Conclusion
It is concluded that waste collectors generally have a higher physical capacity than workers without physically heavy work. A selection may thus take place and moreover, the job seems to have a training effect on the muscle strength—particularly on the shoulder muscles, while this is not the case for the aerobic power. The practical consequences thus indicate that if the job demand is not reduced corresponding to the decrease in aerobic power, the relative workload among elderly workers will be
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