Postcontraction changes of muscle architecture in human quadriceps muscle.

Maximal voluntary contraction changes the mechanical properties of skeletal muscle. Using ultrasound, we investigated whether these changes are reflected by changes in muscle architecture in the vastus lateralis muscle of 8 healthy volunteers. The mean pennation angle during the time interval from 3 to 6 min after maximal voluntary contraction (late postcontraction state) was 14.4 +/- 1.11 degrees (mean +/- SEM) and differed significantly from the precontraction state (16.2 +/- 1.39 degrees ), but the pennation angle in the early postcontraction state did not change statistically from the precontraction angle. Thus, postcontraction changes of the muscle-tendon interface appeared for 6 min after a maximal contraction, which may be important for biomechanical optimization of force transmission in vivo.