PRELOADING AND RANGE OF MOTION EFFECT ON PLANTARFLEXOR MUSCLE PERFORMANCE

Objective: To determine the effects of maximal preloading and range of motion (ROM) on the mechanical parameters of the plantarflexor muscle s obtained while using the isotonic mode of testing of a Biodex dynamo meter. Design: A convenience sample of healthy subjects in the context of a descriptive comparative study. Setting: Research laboratory in C anada. Subjects: Fifteen volunteered subjects without history of injur y or disorder to the right lower extremity. Measurements: I;our maxima l isotonic tests were performed against a selected load of 27Nm. For t he first two tests, die movement at the ankle ranged from -12 degrees (dorsiflexion) to +32 degrees (plantarflexion): one of these tests was preceded by a 2-second maximal preloading contraction, while the othe r was performed without preloading. For the other two tests, the ROM a t the ankle was increased by 15 degrees of plantarflexion and thus ran ged from -12 degrees to +47 degrees; again one of these tests was exec uted with preloading and the other without preloading. Results: The fo ur tests showed differences in the mechanical parameters (MANOVA p < . 05). At angles of -10 degrees and +5 degrees, subjects produced higher torque and power but lower velocity values for the two tests preceded by a maximal preloading. The effect of ROM was demonstrated at +20 de grees where tests performed in a small amplitude reached a lower veloc ity than the corresponding tests performed in a larger amplitude. Base d on the velocity profiles. the results also revealed that maximal pre loading changed the selected isotonic movement of the Biodex dynamomet er to an isoaccelerative movement characterized by high torque and pow er production. Conclusions: Isotonic assessment using the Biodex dynam ometer provides different values of torque, velocity, and power depend ing on the testing conditions used. In clinical settings. it would be important to control these testing conditions. (C) 1996 by the America n Congress of Rehabilitation Medicine and the American Academy of Phys ical Medicine and Rehabilitation