Physical behaviors and fundamental movement skills in British and Iranian children: An isotemporal substitution analysis.

Although the relationship between fundamental movement skills (FMS) and physical behaviors has been established, differences between countries are scarcely explored. The impact of the whole physical behavior composition, in relation to FMS, has yet to be investigated in 9-11 y children. The aims were to investigate the associations of substitution of physical behaviors with FMS score and to compare traditional linear regression and compositional data analysis and compare between England and Iran. Measures included accelerometer-derived activity (sleep (SL), sedentary behavior (SB), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) and FMS, using the TGMD-2, in 119 children (64 boys) from Iran (mean (±SD) age: 9.8 ± 0.3 y; BMI of 18.2 ± 3.3 kg/m ) and 139 (61 boys) children from England (mean (±SD) age: 9.5 ± 0.6 y; BMI of 17.7 ± 3.1 kg/m ). Isometric log-ratio multiple linear regression models were used to discern the association between FMS and the mean activity composition, and for new compositions, where fixed durations of time were reallocated from one behavior to another, while the remaining behaviors were unchanged. In physical behaviors as a composition, FMS was significantly associated in both ethnicities. English children responded significantly positively to adding 5 or more minutes LPA at the expense of SB (FMS unit change from 0.05 [0.01, 0.09] at 5 minutes to 0.72 [0.01, 1.34] at 60 minutes). Adding 10 minutes or more of SL, at the expense of SB, was associated with a significant, positive change in FMS in all children. Investigation is needed to understand the composition of SB and its potential influence on FMS development.