5.5. Association between occupational physical activity and fitness in young adults (IV)

The mean value of the heart rate after step test was 146 beats/min (SD 17) in males and 149 beats/min (SD 18) in females, and the mean handgrip strength was 501 N (SD 87) in males and 285 N (SD 63) in females (article IV: tables 3 and 4). 399 males (19%) and 705 females (39%) reached the maximum time of four minutes in the trunk extension test.

The percentages of males and females, respectively, in different classes of occupational physical activity were (1) light sedentary work: 29% and 36%, (2) other sedentary work: 11% and 7%, (3) light standing or moving work: 13% and 21%, (4) medium heavy moving work: 20% and 23%, (5) heavy manual work: 20% and 12% and (6) very heavy manual work: 7% and 2%.

Males engaged in heavy or very heavy manual work were more often inactive and less often active during their leisure time, compared with males engaged in light sedentary work (Article IV: Table 2 and Fig. 1). In females the trend was similar, but less pronounced.

Step test. Occupational physical activity was associated with the result of the step test in males (p < 0.001) and in females (p = 0.037) after adjustment for leisure-time physical activity, body height and weight and smoking (Article IV: Table 5). The adjusted results of Figure 6 show a 5% decline in heart rate from lowest to highest occupational activity groups in males, while in females a decline in heart rate is recorded mainly in those doing very heavy work.

Handgrip test. Heavy physical work was associated with greater handgrip strength in males (p < 0.001), but not in females (p = 0.065), although the females who did very heavy work showed a relatively high value (Fig. 8, Article IV: Table 6).

Trunk extension test. Males and females who reached the maximum time of four minutes in the test were treated as censored in the Cox regression analyses. Plots of log/ -log hazards suggested no violation of the assumption of proportional hazards. Occupational physical activity was significantly associated with the trunk extension test in males, independently of other factors (p = 0.029), males doing very heavy manual work having a 27% lower risk of failure than males doing light sedentary work (Fig. 8, Article IV: Table 7). The adjusted analysis revealed no significant association between occupational physical activity and the trunk extension test in females (p = 0.153) (Article IV: Table 7), but an isolated high value was seen in women doing heavy sedentary work (Fig. 8).