The relationship of age and level of physical activity with the fractionated components of patellar reflex time.

Sixty male subjects were placed into four equal groups based upon age and level of physical activity: Old Active, Old Inactive, Young Active, and Young Inactive. The criterion measure of total patellar reflex time was fractionated into a central component, reflex latency, and a peripheral component, reflex motor time. Subjects were tested on 2 separate days and on each day, two blocks of ten patellar reflex trials were taken alternating trials between normal and Jendrassik conditions. A split plot analysis of variance showed that no statistically significant differences were found between any group for either of the fractionated components. Also, the amount of Jendrassik facilitation was similar for all four groups. The results suggested that the entire patellar stretch reflex apparatus and the system of alpha-gamma linkage may be unaffected by age and level of activity.