Table 3 .

Predictions for jumping 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 downward-directed force	Decreased forces cervical muscles must produce to maintain postural stabilization	Decrease in activity of cervical muscles relative to control trials	No change in activity of cervical muscles relative to control trials