Cardiorespiratory fitness, aerobic load, & age

Research on the prevention of all-cause mortality and cardiovascular disease indicate associations with capacity-related phenomena, therefore, people with a daily aerobic capacity-load imbalance – such as older workers with a high physical workload – may be exposed to a greater risk of poor health outcomes. Although laboratory studies show a clear relationship between aerobic capacity and aerobic load, it has not been verified in non-laboratory settings. We aimed to verify the transferability of laboratory-based findings to an occupational setting, while also examining the effect of age.
Data of 840 workers from the DPhacto cohort in the Danish cleaning, manufacturing, and transportation sectors were included in analysis. Aerobic capacity, measured using a submaximal cycle ergometer assessment, was followed by four consecutive days of 24-hour heart rate measurement, used for estimating; mean and maximum levels of relative aerobic workload (percentage of heart rate reserve (%HRR)) during occupational hours and the duration (work hours) of high occupational aerobic workload (≥30% HRR). Compositional data analysis was conducted using multivariate linear regression models.
Higher aerobic capacity was significantly associated with decreased mean -0.32 [95%CI: -0.39 to -0.25] and maximum %HRR -0.35[95%CI: -0.45 to -0.25] at work as well as a decreased amount of high occupational aerobic workload -1.8% [95%CI: -2.2 to -1.5%] Across age groups, a ‘u-shape’ relationship was observed, with the strongest association for workers between the ages of 46 and 51.
Significant associations between aerobic capacity and levels of aerobic workload were found using free-living measurements of workers from the cleaning, manufacturing, and transportation sectors in Denmark.