Table 2.

Conditional linear regression models for motor skill development indicators and leisure-time physical activity. The models are presented for both the FT12 and FT16 studies. Only the healthy MZ and same-sexed DZ twin pairs were included in the analyses.

	Leisure-time physical activity (MET hours/day)
	FT12 mean age 24.2 years		FT16 mean age 24.5 years		FT16 mean age 34.0 years		Pooled FT12 and FT16 mean age 24.4 years
	Regression coefficient (95% CI)	p-value	Regression coefficient (95% CI)	p-value	Regression coefficient (95% CI)	p-value	Regression coefficient (95% CI)	p-value
Turning over from back to stomach
No covariates	1.61 (-0.60 to 3.82)	0.15	0.63 (-0.05 to 1.30)	0.07	0.32 (-0.29 to 0.92)	0.31	0.85 (0.22 to 1.47)	0.007
Birth weight + birth order	1.58 (-0.68 to 3.86)	0.17	0.60 (-0.08 to 1.28)	0.08	0.28 (-0.33 to 0.89)	0.37	0.81 (0.17 to 1.44)	0.01
Standing unaided
No covariates	1.86 (0.31 to 3.40)	0.02	1.06 (0.44 to 1.67)	0.001	0.37 (-0.21 to 0.94)	0.21	1.16 (0.63 to 1.7)	<0.001
Birth weight + birth order	1.48 (-0.14 to 3.10)	0.07	1.02 (0.39 to 1.65)	0.002	0.43 (-0.16 to 1.02)	0.15	1.10 (0.55 to 1.64)	<0.001
Walking unaided
No covariates	1.38 (0.15 to 2.62)	0.03	0.23 (-0.21 to 0.67)	0.30	0.11 (-0.33 to 0.54)	0.63	0.49 (0.05 to 0.93)	0.03
Birth weight + birth order	1.32 (0.01 to 2.62)	0.05	0.17 (-0.27 to 0.62)	0.45	0.09 (-0.35 to 0.53)	0.69	0.42 (-0.03 to 0.87)	0.07
Climbing stairs unaided
No covariates	1.56 (-1.32 to 4.45)	0.28	0.91 (0.03 to 1.78)	0.04	0.31(-0.52 to 1.13)	0.46	1.03 (0.24 to 1.81)	0.01
Birth weight + birth order	1.09 (-1.58 to 3.76)	0.42	0.94 (0.06 to 1.82)	0.04	0.34 (-0.51 to 1.18)	0.43	1.00 (0.20 to 1.79)	0.01
Fundamental motor skills at age 6
No covariates	1.36 (-0.20 to 2.93)	0.09	0.84 (0.26 to 1.44)	0.005	0.36 (-0.19 to 0.92)	0.2	0.96 (0.35 to 1.57)	0.002
Birth weight + birth order	1.42 (-0.13 to 2.96)	0.07	0.94 (0.35 to 1.52)	0.002	0.37 (-0.18 to 0.93)	0.19	1.02 (0.41 to 1.63)	0.001
Agility at age 10 (FT12)/at age 12 (FT16)
No covariates	1.25 (-0.08 to 2.59)	0.06	0.68 (0.13 to 1.23)	0.02	0.50 (0.04 to 0.96)	0.03	0.85 (0.33 to 1.37)	0.001
Birth weight + birth order	1.28 (-0.04 to 2.59)	0.06	0.79 (0.25 to 1.33)	0.004	0.55 (0.06 to 1.04)	0.03	0.97 (0.44 to 1.49)	<0.001
Strength at age 10 (FT12)/at age 12 (FT16)
No covariates	0.66 (-0.50 to 1.82)	0.26	0.31 (-0.22 to 0.82)	0.25	0.53 (0.06 to 0.99)	0.03	0.4 (-0.09 to 0.88)	0.11
Birth weight + birth order	0.30 (-0.82 to 1.42)	0.59	0.14 (-0.44 to 0.73)	0.63	0.39 (-0.11 to 0.89)	0.13	0.22 (-0.3 to 0.73)	0.41

MET=metabolic equivalent, CI=confidence intervals