Table 2.

Predictions for running experiments

Experiment	Force manipulation	Prediction of postural stabilization hypothesis	Prediction of core stabilization hypothesis
Added head mass	Increased forces cervical muscles must produce to maintain postural stabilization	Increase in activity of cervical muscles relative to control trials	No change in activity of cervical muscles relative to control trials
Added forward-directed force	Increased flexion moments applied to hip joint	No change in activity of cervical muscles relative to control trials	Increase in activity of cervical hypaxial muscles relative to control trials
Added rearward-directed force	Increased extension moments applied to hip joint	No change in activity of cervical muscles relative to control trials	Increase in activity of cervical epaxial muscles relative to control trials
Added head mass and forward-directed force	Increased forces cervical muscles must produce to maintain postural stabilization in forward-directed force trials	Increase in activity of cervical muscles relative to forward-directed pull trials	No change in activity of cervical muscles relative to forward-directed pull trials
Added head mass and rearward-directed force	Increased forces cervical muscles must produce to maintain postural stabilization in forward-directed force trials	Increase in activity of cervical muscles relative to rearward-directed pull trials	No change in activity of cervical muscles relative to rearward-directed pull trials