In the matrix of relations between the physiology, anatomy, and behavior of the older nervous system, a particular vantage point is research on the-slowness of behavior with age. A review of the evidence indicates that the slowing of behavior with age not only appears in motor responses and sensory processes but becomes more obvious with increasing complexity of behavior. For this reason the expression "slowness of behavior with age" is preferred to the more limited phrase "changes in reaction time with age." While there are probably both general and specific factors in behavioral slowing with age, the organization of a general factor of slowness raises some fundamental questions. Behavioral factors are apparently involved, but more recent emphasis has been placed on the role of neurobiological changes in the central nervous system.

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This experiment sought to determine if posture- and exercise-induced neuro-stimulation influences age differences in reaction (RT) and movement (MT) time, and whether obtained effects varied with physical fitness level. Thirty-six healthy male participants (18 young (19–29 yrs) and 18 old (60–69 yrs), with each group divided into the fit or unfit) performed both simple and two-choice visual reaction time tasks under six arousal/activation conditions: three postural changes (supine, sitting, standing) and three different relative workloads on a cycle ergometer (free pedaling, 20% HRRmax, 40% HRRmax). Consistently, RTs were slower for the older vs. young adults but the elderly performed fastest when Standing than when Sitting or Lying, whereas posture effects were negligible in the young. During exercise SRTs in the young and Old Fit were not greatly influenced by fitness level or arousal/activation condition, but the Old Unfit benefitted from moderate (20% HRRmax) exercise-induced neuromuscular activation thereby accounting for a portion of age-related cognitive slowing by providing evidence that the elderly function at a less activated (aroused) level than young adults and may benefit from circumstances which elevate these levels. An opposite pattern occurred in MTs for the Old Unfit - for both posture and exercise: increases in arousal/activation caused increases in MT but in a fashion not supporting an RT-MT tradeoff in response strategy. Posture and exercise does affect speed of response, and may reduce age differences especially for those who possess already slowed response latencies.