Abstract
BACKGROUND: Walking is a complex act that requires the coordination of locomotor, cardiovascular, and autonomic systems. Aging affects each of these systems and may alter physiological mechanisms regulating the interactions between them. METHODS: We examined the effects of healthy aging on cardiac-locomotor coupling using treadmill walking at incremental speeds from 0.8 mph to normal walking speed in 12 healthy young (29.0 +/- 5.0 years) and 9 healthy elderly persons (70.3 +/- 5.1 years). interbeat (R-R) intervals, step intervals, maximum foot pressure (MFP) and normalized maximum force, blood pressure (BP), and blood flow velocity (BFV) in the middle cerebral artery were continuously measured. RESULTS: Step intervals and R-R intervals decreased, and MFP and BFV increased with walking speed in both groups; systolic BP increased (p <.0001) in the old group. In elderly, but not in young participants, step intervals and R-R intervals were coupled (R(2) = 0.84, p <.0001), and MFP was correlated with systolic BP (R(2) = 0.51, p <.02). CONCLUSION: Cardiolocomotor coupling that becomes manifest with aging may optimize cardiovascular responses during walking. In elderly people, forces generated during the gait cycle may be transmitted to arterial pressure and thus synchronize the central cardiovascular network with the stepping rhythm.