title: Bimodal recovery pattern in human skeletal muscle induced by exhaustive stretch-shortening cycle exercise.
abstract: OBJECTIVE
  Recovery of force and stretch reflex from exhaustive stretch-shortening cycle (SSC) exercise is usually bimodal, characterized as immediate exercise-induced performance reduction, with its quick recovery followed by a longer-lasting reduction in performance. A clear parallel exists between the respective changes in performance, neural activation, and metabolic or structural exercise-induced changes. This implies the existence of potential coupling between muscle failure and the induced neural adjustments that take place along its recovery. The present study was designed to explore the evidence of this coupling more thoroughly.
  
  
  METHODS
  H- and stretch reflexes were measured before and periodically after exhaustive SSC exercise in human subjects. Several markers of muscle damage and inflammation were also measured during the 8-d postexercise follow-up period.
  
  
  RESULTS
  The results indicate that acute changes of H- and stretch reflex patterns and maximal isometric force are associated with significant increases in lactate, interleukin 6, and prostaglandin E2 concentrations. The delayed changes in reflexes and isometric force occurred concomitantly with increases in muscle thickness, C reactive protein, and substance P concentrations and also in serum creatine kinase activity.
  
  
  CONCLUSIONS
  The immediate postexercise decreases in H- and stretch reflexes are probably partially caused by activation of group III and IV afferent fibers by high lactate concentration in combination with possible increases in potassium outflow. Both of these parameters recovered quickly (i.e., 2 h after exercise). The events after the 2-h postexercise point are very likely to be related to muscle damage and associated inflammation. Group III and IV afferent fibers are probably reactivated during this period by mechanical factors.
authors.affiliation: Neuromuscular Research Centre, Department of Biology of Physical Activity, University of Jyväskylä, Finland. Herpola@sport.jyu.fi
authors.forename: Erick
authors.initials: E
authors.lastname: Dousset
authors.forename: Janne
authors.initials: J
authors.lastname: Avela
authors.forename: Masaki
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Jouni
authors.initials: J
authors.lastname: Kallio
authors.forename: Sami
authors.initials: S
authors.lastname: Kuitunen
authors.forename: Heikki
authors.initials: H
authors.lastname: Kyröláinen
authors.forename: Vesa
authors.initials: V
authors.lastname: Linnamo
authors.forename: Paavo V
authors.initials: PV
authors.lastname: Komi
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000503:physiopathology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology*