How could we explain the mechanism driving the effects of Urban Green Space (UGS) on human health? This mechanism is a complex one suggesting, on one hand, an indirect effect of UGS Provision (measured as quantity, quality or accessibility of UGS) on health through UGS Exposure (measured as visit frequency to UGS, duration of visit or intensity of activities taking place during the visit). On the other hand, UGS Provision may have an indirect effect on Exposure, mediated by people’s perception of UGS. The mechanism further suggests that UGS Exposure may influence indirectly human Health but mediated by human motivation to use UGS. We tested these different expectations by fitting 12 alternative structural equation models (SEMs) corresponding to four different scenarios, depending on how UGS Provision was approximated. We show that SEMs where i) Provision is approximated as UGS quantity, and Exposure as duration (SEM_i), ii) Provision is approximated as quantity, and Exposure as intensity (SEM_ii) and iii) Provision is approximated as distance of the closest UGS from people’s house, and Exposure as intensity (SEM_iii) are equally the best of all 12 SEMs tested. However, apart from the SEM_i that has no significant path, SEM_ii and SEM_iii have the same significant path (motivation ~ intensity; β = 7.86±2.03, p = 0.0002), suggesting that visits to UGS may be motivated by opportunities of physical activities offered by UGS. In all our scenarios, the best SEM is always the one where Exposure is measured as intensity, irrespective of how Provision is approximated. This suggests that it is not only UGS provision that matters the most in the mechanism linking UGS to human health improvement, but rather intensity, i.e. the type of activities people engage in when they visit UGSs. Overall, our findings support the theoretical model tested in this study.

我们如何解释驱动城市绿色空间（UGS）对人类健康的影响的机制？这种机制是一个复杂的机制，一方面表明，UGS暴露（通过对UGS的访问频率，对访问的持续时间或活动强度来衡量）对UGS的间接影响（以UGS的数量，质量或可及性衡量）对健康的间接影响访问期间放置）。另一方面，由于人们对UGS的理解，UGS条款可能会对暴露产生间接影响。该机制进一步表明，UGS暴露可能间接影响人类健康，但受人类使用UGS的动机影响。我们通过对12种替代结构方程模型（SEM）进行拟合，测试了这些不同的期望，这些模型分别对应于四种不同的情况，具体取决于如何近似估算UGS条款。_i），ii）提供量近似为数量，暴露量为强度（SEM _ii）和iii）提供量近似为最近的UGS与人居的距离，暴露量为强度（SEM _iii）同样是所有12种方法中最好的扫描电镜测试。但是，除了没有明显路径的SEM _i外，SEM _ii和SEM _iii具有相同的显着路径（动机〜强度；β= 7.86±2.03，p = 0.0002），这表明访问UGS可能是由于UGS提供的体育活动的机会所致。在我们所有的方案中，最好的SEM始终是将暴露量作为强度进行测量的SEM，而与如何估算拨备无关。这表明，在将UGS与改善人类健康联系起来的机制中，最重要的不仅是UGS规定，还包括强度，即人们访问UGS时从事的活动类型。总体而言，我们的发现支持本研究中测试的理论模型。