Status and Trends of Physical Activity Surveillance, Policy, and Research in 164 Countries: Findings From the Global Observatory for Physical Activity—GoPA! 2015 and 2020 Surveys

Background: Physical activity (PA) surveillance, policy, and research efforts need to be periodically appraised to gain insight into national and global capacities for PA promotion. The aim of this paper was to assess the status and trends in PA surveillance, policy, and research in 164 countries. Methods: We used data from the Global Observatory for Physical Activity (GoPA!) 2015 and 2020 surveys. Comprehensive searches were performed for each country to determine the level of development of their PA surveillance, policy, and research, and the findings were verified by the GoPA! Country Contacts. Trends were analyzed based on the data available for both survey years. Results: The global 5-year progress in all 3 indicators was modest, with most countries either improving or staying at the same level. PA surveillance, policy, and research improved or remained at a high level in 48.1%, 40.6%, and 42.1% of the countries, respectively. PA surveillance, policy, and research scores decreased or remained at a low level in 8.3%, 15.8%, and 28.6% of the countries, respectively. The highest capacity for PA promotion was found in Europe, the lowest in Africa and low- and lower-middle-income countries. Although a large percentage of the world’s population benefit from at least some PA policy, surveillance, and research efforts in their countries, 49.6 million people are without PA surveillance, 629.4 million people are without PA policy, and 108.7 million live in countries without any PA research output. A total of 6.3 billion people or 88.2% of the world’s population live in countries where PA promotion capacity should be significantly improved. Conclusion: Despite PA is essential for health, there are large inequalities between countries and world regions in their capacity to promote PA. Coordinated efforts are needed to reduce the inequalities and improve the global capacity for PA promotion

Influence of the geometrical parameters on the conductivity percolation threshold

In our previous work we investigated numerically the influence of the steric properties of conducting particles in a non-conducting host matrix on the electrical conductivity threshold of the material, especially in regard to the shape and orientational order of the particles. In the present work we consider theoretically some additional geometrical aspects of the percolation problem. As regards the percolation threshold itself, we consider three aspects: the probability of inter-penetration of half-soft conducting particles for different penetration depths (penetration probability function), different kinds of inhomogeneous distribution of particles in non-conducting host, size effects, and the agglomeration of conducting particles. We also analyze the size of the conducting-particles' clusters below and above the percolation threshold and compare some characteristic critical exponents with the results in the literature

Numerical analysis of steric influence on conductivity percolation threshold

We have investigated the influence of the steric properties of conducting particles in a nonconducting host matrix on the conductivity threshold of the material, i.e., the minimum volume fraction of conducting phase for the whole sample to become conducting. A statistical, numerical method is used in which the particles are randomly put, one by one, into the nonconducting host and the conducting path is searched. The particles are allowed to penetrate each other to some extent. Three different types of particle shapes are considered: spherical, cylindrical with rounded ends and asymmetric cuboids with rounded surfaces. We have found that in addition to the anisotropy in the particles' dimensions, the angular distribution of the particles' long axes plays a dominant role in the calculations of the conductivity percolation threshold