Activation of human quadriceps femoris during isometric, concentric, and eccentric contractions

J Appl Physiol (1985). 2001 Dec;91(6):2628-34. doi: 10.1152/jappl.2001.91.6.2628.


Maximal and submaximal activation level of the right knee-extensor muscle group were studied during isometric and slow isokinetic muscular contractions in eight male subjects. The activation level was quantified by means of the twitch interpolation technique. A single electrical impulse was delivered, whatever the contraction mode, on the femoral nerve at a constant 50 degrees knee flexion (0 degrees = full extension). Concentric, eccentric (both at 20 degrees /s velocity), and isometric voluntary activation levels were then calculated. The mean activation levels during maximal eccentric and maximal concentric contractions were 88.3 and 89.7%, respectively, and were significantly lower (P < 0.05) with respect to maximal isometric contractions (95.2%). The relationship between voluntary activation levels and submaximal torques was linearly fitted (P < 0.01): comparison of slopes indicated lower activation levels during submaximal eccentric compared with isometric or concentric contractions. It is concluded that reduced neural drive is present during 20 degrees /s maximal concentric and both maximal and submaximal eccentric contractions. These results indicate a voluntary activation dependency on both tension levels and type of muscular actions in the human knee-extensor muscle group.

MeSH terms

  • Adult
  • Electric Stimulation
  • Humans
  • Isometric Contraction / physiology
  • Knee / physiology
  • Leg*
  • Male
  • Muscle Contraction / physiology*
  • Muscle, Skeletal / physiology*
  • Rest
  • Torque