Recent evidence suggests an occupational physical activity (OPA) health paradox where OPA is associated with adverse cardiovascular health. Physiological mechanisms to explain this paradox have not been studied.
METHODS: Nineteen male workers (68% White/Caucasian, age=46.6 years, BMI=27.9 kg/m2) with high reported OPA completed a submaximal exercise test and wore ambulatory activity (ActiGraph and activPAL) and cardiovascular (blood pressure (BP) and heart rate (HR)) monitors for 7days, including at least one workday and non-workday. Individuals recorded work stress levels, work-time, nonwork-time, and sleep times in a diary. Physical activity profiles were described and compared to aerobic physical activity and OPA recommendations. 24-hour cardiovascular load (HR, systolic and diastolic BP) and nocturnal HRV were compared on workdays vs. non-workdays using adjusted linear mixed models. Effect modification by fitness level was explored using interaction models. The effect of work-related stress was analyzed by comparing workdays with low and high stress to non-workdays.
RESULTS: Participants were significantly less sedentary and more active on workdays vs. non-workdays (all p<0.05). While most participants met aerobic activity guidelines, OPA exceeded recommended intensity level and upright time limits. 24-hour HR and diastolic BP were significantly higher on workdays vs. non-workdays (β=5.4 beats/min, p<0.001 and β=2.7 mmHg, p=0.019, respectively) but systolic BP did not differ (β=2.0 mmHg, p=0.317). Nocturnal HRV (low and high frequency power) was significantly lower on workdays vs. non-workdays (β=-0.27, p=0.025 and β=-0.33, p=0.014, respectively); other parameters (RMSSD, SDNN, LF/HF) were similar. Workday vs. non-workday cardiovascular load was not modified by fitness level (p-for-interactions>0.703). When stratified by stress level and compared to non-workdays, 24-hour HR was elevated on both low- (β=4.7 beats/min, p<0.002) and high-stress workdays (β=5.4 beats/min, p<0.001), 24-hour diastolic BP was only elevated on high-stress workdays (β=4.4 mmHg, p=0.023), and 24-hour systolic BP was never elevated (p>0.05).
CONCLUSIONS: Activity was higher and exceeded OPA recommendations on workdays versus non-workdays. Workdays were also associated with elevated 24-hour cardiovascular load and reduced HRV. Fitness did not modify this relationship, but high job stress seemed to exaggerate it. These results suggest high 24-hour cardiovascular load and job stress as potential mechanisms contributing to the OPA health paradox.
|Advisor:||Barone Gibbs, Bethany|
|Commitee:||Kline, Christopher E., Nagle, Elizabeth, Radonovich, Lew|
|School:||University of Pittsburgh|
|Department:||School of Education|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 82/3(E), Dissertation Abstracts International|
|Subjects:||Kinesiology, Occupational safety, Public health|
|Keywords:||Ambulatory Blood Pressure, Heart Rate Variability, Leisure Time Physical Activity, Occupational Physical Activity, Paradox|
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