Abstract MP64: Cardiovascular Responses to Occupational Physical Activity Are Exaggerated by Work-Related Stress and Low Fitness

Introduction: Proposed mechanisms explaining the link between high occupational physical activity (OPA) and cardiovascular disease hypothesize that high work-related stress and low worker fitness may exacerbate cardiovascular responses to OPA. Hypothesis: Direct associations between OPA and acute cardiovascular responses will be stronger under high work-related stress and in workers with lower fitness. Methods: 19 male workers (age=46.6±7.9, 68.4% White) with high OPA jobs were observed for seven days. Steps, light (LPA), and moderate-to-vigorous physical activity (MVPA) during work were measured using a thigh-worn activPAL3 micro, hip-worn Actigraph GT3X-BT, and time-use diary. Heart rate (HR) was measured continuously with a Polar chest strap. 24-hour blood pressure (BP) was measured using an ambulatory BP monitor on one workday. Rate-pressure product (RPP), an indirect measure of cardiac workload, was calculated as systolic BP x HR. Daily work-related stress was measured with the Stress in General Scale (scores=-3-21 where higher scores indicate more stress). Worker fitness was estimated as VO 2 max (ml·kg -1 ·min -1 ) using a submaximal treadmill test. Effect modification by stress and fitness on the associations between OPA and RPP was examined using mixed effects models with interaction terms. Results: Work-related stress was directly associated with 24-hour RPP (β=94.10 mmHg*bpm/stress point, p=0.024) while worker fitness was not (β=-33.0 mmHg*bpm/VO 2 max, p=0.561). Direct association between RPP and occupational MVPA were stronger with higher work-related stress and lower fitness (Table 1, p-for-interaction<0.05 for all). Lower intensity OPA (steps and LPA) were also associated with exacerbated RPP responses outside of work with higher work-related stress (Table 1, p-for-interaction<0.001 for all). Conclusions: OPA performed under high stress or by workers with low fitness may exaggerate cardiovascular responses and contribute to OPA's paradoxical cardiovascular health associations.