title: Differential effects of low-magnitude high-frequency vibration on reloading hind-limb soleus and gastrocnemius medialis muscles in 28-day tail-suspended rats.
abstract: OBJECTIVE
  Low-magnitude high-frequency vibration (LMHFV) was reported beneficial to muscle contractile functions in clinical and preclinical studies. This study aims to investigate the effects of LMHFV on myofibers, myogenic cells and functional properties of disused soleus (Sol) and gastrocnemius medialis (GM) during reloading.
  
  
  METHODS
  Sprague Dawley rats were hind-limb unloaded for 28 days and assigned to reloading control (Ctrl) or LMHFV group (Vib). Sol and GM of both groups were harvested for fiber typing, proliferating myogenic cell counting and in vitro functional assessment.
  
  
  RESULTS
  Myogenic cells proliferation was promoted by LMHFV in both Sol and GM (p<0.001 and p<0.05 respectively). Force generating capacity was not much affected (Vib=Ctrl, p>0.05) but fast-fiber favorable changes in fiber type switching (more type IIA but lower type I in Vib; p<0.05 and 0.01 respectively) and fiber hypertrophy (type I, Vib<Ctrl; p<0.01) were observed mainly in GM.
  
  
  CONCLUSIONS
  LMHFV was not detrimental to reloading muscles but the outcomes were muscle dependent. The unique fiber type composition and anatomical differences between Sol and GM might render the differential muscle responses to LMHFV. Further investigations on myofibers type specific responses to different LMHFV regimes and myogenic cell interaction with associated myofiber were proposed.
authors.affiliation: Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
authors.forename: K T
authors.initials: KT
authors.lastname: Sun
authors.forename: K S
authors.initials: KS
authors.lastname: Leung
authors.forename: P M F
authors.initials: PM
authors.lastname: Siu
authors.forename: L
authors.initials: L
authors.lastname: Qin
authors.forename: W H
authors.initials: WH
authors.lastname: Cheung
mesh_terms: D000818:Animals; D002452:Cell Count; D019417:Hindlimb Suspension / Q000009:adverse effects; D007150:Immunohistochemistry; D008297:Male; D032342:Muscle Cells / Q000473:pathology; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology*; D018657:Muscle Fibers, Slow-Twitch / Q000473:pathology*; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000209:etiology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014732:Vibration