METHODS

The sample comprised 494 men, registered in employment, aged 20–60 years, and resident in the Republic of Croatia. The subjects were sampled by general practitioners. They were asked to send a letter of invitation to every registered employed patient between the ages of 20 and 60. The letter comprised a short description of the procedures, and the time and date of testing. The subjects came from different educational backgrounds and were both smokers and non-smokers. One fifth (21%) of all contacted subjects showed up for testing, which was scheduled in the morning hours. Some subjects had to be excluded because of acute or chronic illness. Also, the subjects that participated regularly in any kind of recreational sport were not evaluated. This resulted in only 71.5% of subjects who came to testing being evaluated.

All examinees were tested by the Baecke questionnaire² for assessment of the level of habitual physical activity. Baecke’s questionnaire was chosen because of its previous positive evaluation in research.³ The questionnaire was composed of 16 items testing the physical load at work, physical load during sport activities, and physical load during leisure time. Three basic indices resulted from the application of this questionnaire: the Work Index, Sport Index, and Leisure Index. The lowest possible value of the indices was 1.0 units, signifying the lowest physical activity, while the highest possible value was 5.0 units, signifying the highest physical activity.

The subjects were divided into two groups. The first group was composed of subjects whose Work Index was lower than 3.0 units, representing a lower physical load in their jobs (n = 220). The second group was determined by a Work Index of 3.0 units and higher, representing a higher physical load in their workplace (n = 274). The EUROFIT battery of tests was used in order to determine flexibility, explosive strength, repetitive strength (sit-ups), handgrip, tapping, balance, and maximal oxygen uptake.⁴ Flexibility was tested by means of the “sit and reach” test, explosive strength by a vertical jump, and maximal oxygen uptake was estimated by the Astrand test.⁴ The one-leg balance test results were gained from a number of trials needed to accomplish 30 seconds of one-leg standing; the lower the value the better the result. The differences between the two groups were tested by ANOVA/MANOVA tests.

RESULTS

The mean value of the first group’s Work Index was 2.32 (SD 0.38) units, while the mean value of the Work Index in the second group was 3.62 (0.41) units; the difference was statistically significant (p < 0.001). The groups did not differ according to age (mean (SD) 42.1 (8.4) years v 41.7 (8.4) years, p = 0.842). Only subjects whose Sport Index equalled zero were included in the study, so we were sure that none of the subjects participated in any kind of sport/recreational physical activity during their leisure time. This was also confirmed by a comparison of the Leisure Indices, which were not significantly different between the groups (mean (SD) 2.72 (0.59) units v 2.64 (0.57) units, p = 0.327), leading to the conclusion that the subjects were spending their leisure time in a similar manner regarding physical activity.

Differences in morphological characteristics that might contribute to the results of the study were also tested. The two groups did not differ according to body mass index (mean (SD) 26.8 (3.4) kg/m²v 27.2 (3.7) kg/m², p = 0.084).

ANOVA showed that the groups differed significantly from each other according to functional and motor abilities (Wilk’s lambda 0.918, Rao’s R 7.152, p < 0.001). The results of the t test for independent samples showed that there was a significant difference present between the groups in all variables except the vertical jump, representing explosive strength. The group with Work Indices of 3.0 units or higher performed significantly worse than the group with Work Indices below 3.0 units. The subjects that had more workload at their workplace had lesser repetitive strength, less balance, and were less flexible than the subjects that had lower Work Indices. The group with high occupational physical load only performed better on the handgrip test. No significant differences were observed in explosive strength and aerobic capacity (table 1).

DISCUSSION

Some workplaces demand a significant amount of physical activity for the performance of daily assignments. This usually consists of time spent standing or walking, lifting heavy weights, or performing manual tasks. This may be the reason for the fact that some workers engaging in manual labour are reluctant to participate in any kind of sport/recreational activity, assuming there is no need for additional physical activity after a heavy day at work.

The fact that subjects with a higher Work Index performed worse on physical fitness testing points to the conclusion that increased physical load at work does not result in better physical abilities. This could be concluded because the subjects in both groups did not participate in any kind of sport/recreational activity and there was no significant difference between the groups according to age. This leads to the assumption that the poorer performance of the subjects with a high Work Index might be attributed to persistent fatigue and chronic changes due to repetitive overload. Similar results were found in women in a previous study.⁵

The physical fitness surveys performed in Sweden and the UK^6,7 did not compare physical load in the workplace with performance. Even so, the published results of these studies show many similarities in the functional and motor abilities of employed men in Sweden, the UK, and Croatia. The results of this study are contradictory to the results of Tammelin and colleagues.⁸ The latter found that better fitness levels were related to higher occupational physical activity. The differences might originate from the fact that their sample was much younger (birth cohort 1966) than the sample in this study. Also, Tammelin and colleagues point to the fact that some studies have suggested a reversal of the positive effect of heavy work on fitness with advancing age. However, our results are consistent with those of Nygard and colleagues,⁹ who concluded that jobs with mainly physical demands do not guarantee superior musculoskeletal capacity in older employees, but in their work the observed differences were not significant.

Finally, the results of this study lead us to conclude that higher physical load in the workplace does not provide adequate intensity, volume, and duration of physical tasks to induce positive changes in the aerobic capacity, strength, or flexibility of subjects. It emphasises the fact that physical activity should be planned and programmed to improve physiological capacities. The results of this study would imply the need for engagement of physically overloaded employees in organised sport/recreational activities that might improve their physical abilities.