EFFECTS OF AGE AND SPEED ON COACTIVATION, VARIABILITY, AND JOINT KINETICS DURING WALKING

Open Access
Author:
Peterson, Daniel S
Graduate Program:
Kinesiology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 21, 2008
Committee Members:
  • Philip Martin, Thesis Advisor
Keywords:
  • Gait
  • metabolic cost
  • coactivation
  • kinetics
Abstract:
Metabolic cost of walking (Cw), defined as the rate of oxygen consumed during walking per unit distance traveled, has been shown to be greater for the elderly than for young adults across a range of walking speeds (Ortega & Farley, 2007; Mian et al., 2006). Several potential causes of increased Cw in older adults have been highlighted in current literature, including elevated antagonistic muscle coactivation, a proximal redistribution of lower limb work, and increased step width variability. The purpose of this study was to investigate age and speed effects on these three variables as well as Cw, and to quantify the relationship between these variables and Cw. Joint kinematics, joint kinetics, lower extremity electromyography, and Cw were measured for fourteen physically active older adults, and fourteen active young adults at four walking speeds (0.89, 1.12, 1.34, and 1.57 m•s-1). Older participants exhibited 23% higher Cw than young adults when averaged across walking speeds. Coactivation was significantly higher about the thigh but not the shank in older adults across all speeds tested. Also, a proximal redistribution of joint work was noted in older adults, as this group exhibited less knee work and more hip work than young. Ankle work, however, was similar between age groups. Step width, step width variability, stride length, and stride length variability were all similar for the two age groups. Cw was positively correlated with coactivation only. Due to the elevated coactivation in older adults, as well as the positive correlations exhibited between this variable and Cw, it seems as if coactivation may be a factor in the increased Cw seen in older adults.