COMPARISON OF MUSCLE AND TENDON STIFFNESS, JUMPING ABILITY, MUSCLE STRENGTH AND FATIGUE IN THE PLANTER FLEXORS

An isokinetic dynamometer was used to measure plantar flexion muscle s trength at 60 degrees/s and 200 degrees/s in 10 healthy young men (mea n age 25 years). Muscle and tendon stiffnesses were determined on the dynamometer by the use of electrical stimulation and passive stretch ( 200 degrees/s). Differences in jumping heights between squat and count er-movement jumps were calculated from flight times. The number of hee l-rises performed until exhaustion, standing on one leg, were counted. Stepwise regression analysis showed that differences in jumping heigh t increased with lower muscle strength and with higher muscle and tend on stiffnesses, indicating that elastic components may be of more impo rtance in persons with lower muscle strength. The number of heel-rises was negatively dependant on tendon stiffness, indicating that increas ed stiffness may enhance the development of fatigue.