Zusammenfassung:
Background and context
We have determined, using 7 years of actual population-based data (from 1997 through 2003), how much daily physical activity in relatively universally performed types of activities would be needed to reduce the prevalence of sedentarity and what would be the impact of the full or partial implementation of a nationally recognized physical activity pyramid.
Methods
We capitalized on our unique physical activity monitoring system in the Geneva general adult (ages 35-74 yrs) population, which is based on a physical activity frequency questionnaire (PAFQ) that was developed and validated in the same target population. We assessed the intensity of physical activity by the energy expenditure (EE) it produces in terms of a multiple of an individual's sex-age-height-weight-specific basal metabolic rate (BMR). The BMR is the resting EE rate. Information was available for 8,528 adults (4,280 men and 4,248 women).
We simulated the maximum potential impact on the population total EE of activities that can be almost universally performed daily, such as walking, bicycling, climbing stairs, etc., corresponding to intensities of 3.5, 3.7, 3.9 and 4 x BMR. For each of the latter intensities, we defined sedentarity as expending <10% of total EE in activities of at least the same intensity. We varied duration (15, 30, 45, 60 minutes per day) and assumed 100% and 50% population campaign participation rates in performing the calculations.
Results
Before accounting for the physical activity pyramid recommendations, 50+% population compliance with 45+ minutes per day of activities of 3.7+ BMR would be needed to reduce the prevalence of sedentarity by at least 20% (from 55% to 44%). If 100% of the population performed 60 minutes of activity of 4+ BMR, sedentarity prevalence would decrease by 77% (from 65% to 15%).
If 50% of the population complied with the recommendations of the physical activity pyramid, the prevalence of sedentarity would decrease by 37%, 36%, 36%, and 35%. For 100% population compliance with activities of 3.5+ BMR 7x30 minutes per week comprising the bottom tier of the physical activity pyramid, the maximum decline would be 74% (from 44% to 11%).
Conclusion
The present study shows that very high levels of physical activity need to be performed by the population to substantially reduce the prevalence of sedentarity. Even full compliance with the physical activity pyramid would not reduce the prevalence of sedentarity by more than 75%. Therefore, the objectives of mass campaigns for increasing physical activity need to distinguish between short vs. middle and long term gains, and should consider the physical activity pyramid as a lower rather than an upper recommended limit of activity target.
