Eccentric and concentric force-velocity relationships of the quadriceps feimoris muscle.

Most functional activities utilize all three types of muscle contraction. The purpose of this study was to examine concentric and eccentric force-velocity relationships of the knee extensors of 30 young, healthy females at seven velocities between 30 and 210 degrees /sec using the Kinetic Communicator. The average force produced by the quadriceps during three concentric and three eccentric contractions was calculated at each velocity. The force-velocity relationships were graphed and analyzed using linear regression techniques. Results showed that the mean slope of the combined linear regression lines of concentric data was -0.55, which is significantly different from a zero slope. This indicates that concentric force of the knee extensors decreases as velocity increases. The mean slope of the combined linear regression lines of the eccentric data was -0.04, indicating no significant change in eccentric force with an increase in velocity. It appears, therefore, that in the knee extensors of healthy, young females, concentric force decreases as velocity increases to 210 degrees /sec, while eccentric force remains the same. Both concentric and eccentric work are often emphasized in strength training programs. It is, therefore, important for professionals involved in the rehabilitation or training of patients and athletes to be aware of differences between eccentric and concentric force-velocity relationships. J Orthop Sports Phys Ther 1992;16(2):82-86.