TABLE 3

Results of the 4 Multilevel Regression Models for Muscle Thickness Development

Biceps BrachiiForearm FlexorsQuadricepsTibialis Anterior
Intercept−3.993−7.522−6.673−3.584
Age−0.0050.163**0.162**0.000
GH0.902**0.906**0.794 **0.455*
Baseline average muscle thickness3.442**5.847 **3.420**3.459**
Age × baseline average muscle thickness−0.145**−0.102**
Between-subject variance intercept0.0180.0020.2000.060
Between-subject variance age0.0010.0000.0000.007
Within-subject variance0.670.280.650.39
Variance empty model1.140.951.280.79
Proportional reduction in unexplained variance,a %41714951
  • Results include the explanatory variables (age, GH, and baseline muscle thickness) and their interactions. Explanatory variables: age = age in months; GH = a Boolean variable (0 = no, 1 = yes); baseline average muscle thickness = sum of muscle thickness per muscle group divided by 4. *P < .01, **P < .001.

  • a The reduction in the unexplained variance when the empty model is compared with the final model.