title: Triceps surae fascicle stretch is poorly correlated with short latency stretch reflex size.
abstract: BACKGROUND
  The short latency stretch reflex (SLR) is well described, but the stimulus that evokes the SLR remains elusive. One hypothesis states that reflex size is proportional to muscle fiber stretch, so in this study we examined the relationship between these 2 parameters in human triceps surae muscles.
  
  
  METHODS
  Achilles tendon taps and dorsiflexion stretches with different amplitudes and preactivation torques were applied to 6 participants while electromyography and muscle fascicle length changes were recorded in soleus and medial gastrocnemius (MG).
  
  
  RESULTS
  In response to tendon taps, neither fascicle length nor velocity changes were correlated with SLR size in either muscle, but accelerometer peaks were observed immediately after hammer-tendon contact. Similar results were obtained after dorsiflexion stretches.
  
  
  CONCLUSIONS
  Muscle fascicle stretch is poorly correlated with SLR size, regardless of perturbation parameters. We attribute the SLR trigger to the transmission of vibration through the lower limb, rather than muscle fiber stretch.
authors.affiliation: Neuromuscular Research Centre, Department of Biology of Physical Activity, University of Viveca, P.O. Box 35, Jyväskylä, 40014, Finland.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Cronin
authors.affiliation: Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia.
authors.forename: Timo
authors.initials: T
authors.lastname: Rantalainen
authors.affiliation: Neuromuscular Research Centre, Department of Biology of Physical Activity, University of Viveca, P.O. Box 35, Jyväskylä, 40014, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Avela
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D008297:Male; D052580:Muscle Stretching Exercises / Q000379:methods; D018482:Muscle, Skeletal / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology*; D013710:Tendons / Q000502:physiology*
keywords: dorsiflexion stretch; muscle fascicle; reflex EMG; tendon tap; ultrasound