OBJECTIVE: To test the hypothesis that changing body weight toward the narrower rearfoot or the wider forefoot causes a decrease or increase in the amount of center of pressure (CoP) displacement per unit of foot tilt (EQ), and to examine the effect on postural control. DESIGN: Experimental, within-subject design with one controlled variable. SETTING: A biomechanics laboratory of a university department of biomedical physics and technology. SUBJECTS: Ten healthy, young subjects. MAIN OUTCOME MEASURES: The sagittal plane position of the CoP (Y) reflecting foot loading, EQ, and horizontal ground reaction forces (Fx) representing postural control. RESULTS: Shifting body weight to the rearfoot or forefoot decreases (d) or increases (i) Y (Pd = .002, Pi = .000) and EQ (Pd = .018, Pi = .064). In both cases Fx (Pd = .008, Pi = .098) increased and postural control deteriorated. CONCLUSIONS: Shifting body weight to the rearfoot or forefoot decreases or increases EQ. Besides the changes in EQ encountered here, other factors are held responsible for the deterioration of postural control. The absence or presence of changes in Y can be used to exclude or include the presence of an effect of EQ or these unknown factors on postural control.
OBJECTIVE: To test the hypothesis that changing body weight toward the narrower rearfoot or the wider forefoot causes a decrease or increase in the amount of center of pressure (CoP) displacement per unit of foot tilt (EQ), and to examine the effect on postural control. DESIGN: Experimental, within-subject design with one controlled variable. SETTING: A biomechanics laboratory of a university department of biomedical physics and technology. SUBJECTS: Ten healthy, young subjects. MAIN OUTCOME MEASURES: The sagittal plane position of the CoP (Y) reflecting foot loading, EQ, and horizontal ground reaction forces (Fx) representing postural control. RESULTS: Shifting body weight to the rearfoot or forefoot decreases (d) or increases (i) Y (Pd = .002, Pi = .000) and EQ (Pd = .018, Pi = .064). In both cases Fx (Pd = .008, Pi = .098) increased and postural control deteriorated. CONCLUSIONS: Shifting body weight to the rearfoot or forefoot decreases or increases EQ. Besides the changes in EQ encountered here, other factors are held responsible for the deterioration of postural control. The absence or presence of changes in Y can be used to exclude or include the presence of an effect of EQ or these unknown factors on postural control.