Fractionated myotatic reflex times in women by activity level and age

A lifetime habit of participation in vigorous physical exercise has been associated with the maintenance of efficient neuromuscular performance into old age. During test sessions on three consecutive days, measures of fractioned patellar (knee-jerk) reflex times under normal and Jendrassik conditions were obtained from 60 female participants classified as old inactive, old active, young inactive, or young active. A three-factor analysis of variance showed that age/activity group differences were present for reflex latency, but not for reflex motor time or total reflex time. Age differences were demonstrated for degree of reflex facilitation resulting from the Jendrassik maneuver. The results demonstrate that the functional reflex is well maintained into the sixth decade, but that sensitivity to Jendrassik facilitation of the pathway is diminished with age.