The effects of green space and physical activity on muscle strength: a national cross-sectional survey with 128,759 Chinese adults

Neighbourhood walkability and greenspace and their associations with health-related fitness in urban dwelling Canadian adults

OBJECTIVE

Muscular strength and body composition are important components of health-related fitness (HRF). Grip strength and body fat percent, in particular, are associated with chronic disease and affected by health behaviours. Evidence suggests relationships between the neighbourhood built environment (BE) and HRF exist, however, few studies have focused on grip strength and body fat percent. Therefore, our study aimed to estimate the sex-specific associations between the neighbourhood BE, grip strength, and body fat percent among urban-dwelling Canadian adults.

METHODS

We analyzed cross-sectional survey and HRF data collected in 2011-2015 from 4052 males and 7841 females (Alberta's Tomorrow Project, Canada). Grip strength and body fat percent were measured via handgrip dynamometry and bioelectrical impedance analysis, respectively. Walkability (Canadian Active Living Index) and greenness (Normalized Difference Vegetation Index) estimates were linked to participant data. Sex-stratified covariate-adjusted linear regression models estimated the associations between the BE and HRF variables.

RESULTS

Walkability was negatively associated with grip strength and body fat percent in males (β -0.21, 95%CI: -0.31 to -0.11 and β -0.08, 95%CI: -0.15 to -0.02, respectively) and females (β -0.06, 95%CI: -0.10 to -0.01 and β -0.08, 95%CI: -0.14 to -0.02, respectively). Greenness was positively associated with grip strength in males (β 6.99, 95%CI: 3.62 to 10.36) and females (β 2.72, 95%CI: 1.22 to 4.22) but not with body fat percent. Controlling for physical activity and sitting did not attenuate these associations.

CONCLUSION

Characteristics of the neighbourhood BE appear to be associated with muscular strength and body composition, independent of physical activity and sedentary behaviour.

Mediation analysis of the associations between neighbourhood walkability and greenness, accelerometer-measured physical activity, and health-related fitness in urban dwelling Canadians

OBJECTIVE

To estimate sex-specific associations (total, direct, and indirect effects) between objectively measured neighbourhood walkability and greenness and objectively measured physical activity and health-related fitness including cardiorespiratory and muscular fitness in Canadian adults.

METHODS

Neighbourhood walkability (Canadian Active Living Environment) and greenness (Normalized Difference Vegetation Index; NDVI) data were linked to cardiorespiratory (i.e., submaximal step test estimated V̇O2 max) and muscular fitness (i.e., handgrip strength) and accelerometer measured physical activity; Canadian Health Measures Survey). Covariate-adjusted sex-stratified path analyses was conducted to assess if physical activity (light: LPA; moderate: MPA, and; vigorous: VPA) mediated the associations between neighbourhood walkability, NDVI and health-related fitness. Model sample sizes ranged from 987 to 2796 for males and 989 to 2835 for females.

RESULTS

Among males, we found indirect effects between neighbourhood walkability and cardiorespiratory fitness via LPA (negative) and VPA (positive). We also found a total effect (negative) between neighbourhood walkability and grip strength and indirect effects between neighbourhood walkability and handgrip strength via LPA (negative) and MPA (negative). Among females, we found a total effect (positive) and direct effect (positive) between neighbourhood walkability and cardiorespiratory fitness, and an indirect effect for neighbourhood walkability and cardiorespiratory fitness via LPA. We found no significant effects related to neighbourhood greenness.

CONCLUSIONS

Residing in a neighbourhood with higher walkability may positively affect cardiorespiratory fitness but negatively affect muscular strength. The negative associations between neighbourhood walkability and LPA may offset potential positive associations between neighbourhood walkability and MPA and VPA and their subsequent influence on health-related fitness.