title: Adaptations of mouse skeletal muscle to low-intensity vibration training.
abstract: OBJECTIVE
  We tested the hypothesis that low-intensity vibration training in mice improves contractile function of hindlimb skeletal muscles and promotes exercise-related cellular adaptations.
  
  
  METHODS
  We subjected C57BL/6J mice to 6 wk, 5 d·wk, 15 min·d of sham or low-intensity vibration (45 Hz, 1.0g) while housed in traditional cages (Sham-Active, n = 8; Vibrated-Active, n = 10) or in small cages to restrict physical activity (Sham-Restricted, n = 8; Vibrated-Restricted, n = 8). Contractile function and resistance to fatigue were tested in vivo (anterior and posterior crural muscles) and ex vivo on the soleus muscle. Tibialis anterior and soleus muscles were evaluated histologically for alterations in oxidative metabolism, capillarity, and fiber types. Epididymal fat pad and hindlimb muscle masses were measured. Two-way ANOVAs were used to determine the effects of vibration and physical inactivity.
  
  
  RESULTS
  Vibration training resulted in a 10% increase in maximal isometric torque (P = 0.038) and 16% faster maximal rate of relaxation (P = 0.030) of the anterior crural muscles. Posterior crural muscles were unaffected by vibration, except greater rates of contraction in Vibrated-Restricted mice compared with Vibrated-Active and Sham-Restricted mice (P = 0.022). Soleus muscle maximal isometric tetanic force tended to be greater (P = 0.057), and maximal relaxation was 20% faster (P = 0.005) in vibrated compared with sham mice. The restriction of physical activity induced muscle weakness but was not required for vibration to be effective in improving strength or relaxation. Vibration training did not affect muscle fatigability or any indicator of cellular adaptation investigated (P ≥ 0.431). Fat pad but not hindlimb muscle masses were affected by vibration training.
  
  
  CONCLUSIONS
  Vibration training in mice improved muscle contractility, specifically strength and relaxation rates, with no indication of adverse effects to muscle function or cellular adaptations.
authors.affiliation: Rehabilitation Science and Program in Physical Therapy, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: James N
authors.initials: JN
authors.lastname: McKeehen
authors.forename: Susan A
authors.initials: SA
authors.lastname: Novotny
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Baltgalvis
authors.forename: Jarrod A
authors.initials: JA
authors.lastname: Call
authors.forename: David J
authors.initials: DJ
authors.lastname: Nuckley
authors.forename: Dawn A
authors.initials: DA
authors.lastname: Lowe
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000295:instrumentation / Q000379:methods*; D011897:Random Allocation; D014732:Vibration
chemical_list: D015415:Biomarkers