Modulation of muscle activity and force fluctuations in the plantarflexors after bedrest depends on knee position

Yasuhide Yoshitake, Motoki Kouzaki, Hideoki Fukuoka, Tetsuo Fukunaga, Minoru Shinohara*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Force fluctuations in leg muscles increase after bedrest, perhaps due to modulation of the neural strategy that is specific to a muscle or common to agonist muscles. The purpose of this study was to examine the modulation of muscle activity and force fluctuations during steady contractions with variable involvement of plantarflexor muscles after bedrest at knee-flexed (FLX) and extended (EXT) positions. Before and after 20-day bedrest, plantarflexion force and surface electromyogram (EMG) in the medial gastrocnemius (MG), lateral gastrocnemius, and soleus muscles were measured during steady isometric contractions in five young men. In EXT, power ≤10 Hz in the rectified EMG of MG increased significantly after bedrest. This low-frequency modulation of muscle activity in MG accompanied a 29% increase in the standard deviation of force. There was no change in EMG in other muscles. In FLX, there was no adjustment in EMG or force fluctuations. These results suggest that low-frequency modulation of MG plays a role in increasing force fluctuations during steady plantarflexion in EXT after bedrest. The findings indicate task/muscle specificity in the modulation of neural strategy during steady contractions after bedrest and underscore the importance of designing a specific training regimen targeted to particular tasks/muscles with regard to force fluctuations in multiple-agonist systems.

Original languageEnglish
Pages (from-to)745-755
Number of pages11
JournalMuscle and Nerve
Issue number6
Publication statusPublished - 2007 Jun
Externally publishedYes


  • Bedrest
  • Muscle length
  • Plantarflexion
  • Steadiness

ASJC Scopus subject areas

  • Clinical Neurology
  • General Neuroscience


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