Strength training reduces intracortical inhibition

Acta Physiol (Oxf). 2012 Oct;206(2):109-19. doi: 10.1111/j.1748-1716.2012.02454.x. Epub 2012 Jun 23.


Aim: Paired-pulse transcranial magnetic stimulation was used to investigate the influence of 4 weeks of heavy load squat strength training on corticospinal excitability and short-interval intracortical inhibition (rectus femoris muscle).

Methods: Participants (n = 12) were randomly allocated to a strength training or control group. The strength training group completed 4 weeks of heavy load squat strength training. Recruitment curves were constructed to determine values for the slope of the curve, V50 and peak height. Short-interval intracortical inhibition was assessed using a subthreshold (0.7 × active motor threshold) conditioning stimulus, followed 3 ms later by a supra-threshold (1.2 × active motor threshold) test stimulus. All motor evoked responses were taken during 10% of maximal voluntary isometric contraction (MVC) torque and normalized to the maximal M-wave.

Results: The strength training group attained 87% increases in 1RM squat strength (P < 0.01), significant increases in measures of corticospinal excitability (1.2 × Motor threshold: 116%, P = 0.016; peak height of recruitment curve = 105%, P < 0.001), and a 32% reduction in short-interval intracortical inhibition (P < 0.01) following the 4-week intervention compared with control. There were no changes in any dependent variable (P > 0.05) detected in the control group.

Conclusion: Repeated high force voluntary muscle activation in the form of short-term strength training reduces short-interval intracortical inhibition. This is consistent with studies involving skilled/complex tasks or novel movement patterns and acute studies investigating acute voluntary contractions.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adaptation, Physiological
  • Adolescent
  • Adult
  • Analysis of Variance
  • Biomechanical Phenomena
  • Cerebral Cortex / physiology*
  • Electromyography
  • Evoked Potentials, Motor
  • Female
  • Humans
  • Isometric Contraction*
  • Male
  • Muscle Strength*
  • Neural Inhibition*
  • Pyramidal Tracts / physiology
  • Quadriceps Muscle / innervation*
  • Recruitment, Neurophysiological
  • Resistance Training*
  • Sensory Thresholds
  • Time Factors
  • Torque
  • Transcranial Magnetic Stimulation
  • Victoria
  • Volition
  • Young Adult