Postactivation potentiation, fiber type, and twitch contraction time in human knee extensor muscles

J Appl Physiol (1985). 2000 Jun;88(6):2131-7. doi: 10.1152/jappl.2000.88.6.2131.

Abstract

In small mammals, muscles with shorter twitch contraction times and a predominance of fast-twitch, type II fibers exhibit greater posttetanic twitch force potentiation than muscles with longer twitch contraction times and a predominance of slow-twitch, type I fibers. In humans, the correlation between potentiation and fiber-type distribution has not been found consistently. In the present study, postactivation potentiation (PAP) was induced in the knee extensors of 20 young men by a 10-s maximum voluntary isometric contraction (MVC). Maximal twitch contractions of the knee extensors were evoked before and after the MVC. A negative correlation (r = -0. 73, P < 0.001) was found between PAP and pre-MVC twitch time to peak torque (TPT). The four men with the highest (HPAP, 104 +/- 11%) and lowest (LPAP, 43 +/- 7%) PAP values (P < 0.0001) underwent needle biopsies of vastus lateralis. HPAP had a greater percentage of type II fibers (72 +/- 9 vs. 39 +/- 7%, P < 0.001) and shorter pre-MVC twitch TPT (61 +/- 12 vs. 86 +/- 7 ms, P < 0.05) than LPAP. These data indicate that, similar to the muscles of small mammals, human muscles with shorter twitch contraction times and a higher percentage of type II fibers exhibit greater PAP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Electromyography
  • Humans
  • Knee / physiology*
  • Male
  • Muscle Contraction / physiology
  • Muscle Fibers, Fast-Twitch / physiology
  • Muscle Fibers, Skeletal / classification*
  • Muscle Fibers, Skeletal / physiology
  • Muscle Fibers, Slow-Twitch / physiology
  • Muscle, Skeletal / physiology*
  • Time Factors