Effect of knee flexion angle on active joint stiffness
by
McHugh MP, Hogan DE.
—
last modified
2009-10-09 15:17
Acta Physiol Scand. 2004 Mar;180(3):249-54.
AIM: The purpose of this study was to determine if active joint stiffness
measured during maximum voluntary knee extension contractions was affected by
knee flexion angle. METHODS: Eighteen subjects volunteered (11 male, seven
female). A stretch was imposed on isometric knee contractions performed at 30
degrees, 50 degrees, 70 degrees, 90 degrees, and 110 degrees of knee flexion.
Active joint stiffness was computed from the increase in torque relative to the
change in knee flexion angle for the first 50 ms of the stretch (approximately
1.5 degrees ) and corrected for effects of gravitational component due to leg
mass and passive tension. RESULTS: There was a plateau in knee extension torque
between 70 degrees and 90 degrees with lower values at all other angles (P <
0.05). Peak active joint stiffness occurred at 70 degrees with lower values (P <
0.05) at all other angles except 50 degrees. Stiffness at 70 degrees (441.1 +/-
189.9 Nm rad-1) was 49% higher than at 30 degrees and 45% higher than at 110
degrees. CONCLUSION: Active joint stiffness was dependent on knee flexion angle.
Peak joint stiffness during maximal contractions occurred at, or prior to, the
optimal angle for torque production for all subjects.