Kinematic characterization of standing reach: comparison of younger vs. older subjects

Objective. To characterize typical spinal motions that occur during standing reach and to describe differences in spinal motions and center of pressure displacements during reach between younger and older healthy adults. Design. Exploratory, cross sectional investigation utilizing video motion and biomechanics force platform analysis. Background. Standing reach provides a means for assessing both arm function and balance control in the context of a common functional activity. The interaction between age-related declines in spinal mobility and the spinal motion occurring during reach is poorly understood. The characterization of spinal motions during task performance for healthy subjects of different age groups is an important first step for understanding the relationship between impairments and physical performance in disabled populations. Methods. Thirty-four subjects ages 20–36 and 33 subjects ages 60–76 participated. Video motion and force plate analysis were used to characterize spinal motion and center of pressure displacements during the functional reach test for younger and older subjects. Results. Spinal motion during standing reach was characterized by forward trunk flexion, lateral trunk flexion, thoracolumbar rotation, and lower body rotation. Younger and older subjects differed (P=0.05) in the amount of forward trunk flexion and thoracolumbar rotation which occurred but not lower body rotation. Younger subjects displaced their center of pressure further forward (P=0.0001) and through a greater percentage of their initial base of support (P=0.0001) than older subjects. Conclusion. This study provides the first multiplanar characterization of spinal motion used during standing reach. Significant differences for a number of variables existed between younger and older subjects.