title: Effects of flexibility training on eccentric exercise-induced muscle damage.
abstract: OBJECTIVE
  This study investigated whether flexibility training would attenuate muscle damage induced by maximal eccentric exercise.
  
  
  METHODS
  Thirty untrained young men were allocated to static stretching (SS), proprioceptive neuromuscular facilitation (PNF), or control group (n = 10 per group). The SS consisted of 30 sets of a 30-s standard SS with a 30-s rest between sets, and the PNF included 5 sets of the 30-s standard SS followed by 3 sets of three "contract-relax-agonist-contract" procedures. These were performed three times a week for 8 wk, and all subjects performed six sets of 10 maximal isokinetic (30°·s) lengthening contractions of the knee flexors after the 8-wk training or 8 wk after the baseline measures (control). Changes in indirect markers of muscle damage before and for 5 d after the eccentric exercise were compared among the groups.
  
  
  RESULTS
  The range of motion (ROM) of the hip joint increased by 25°, and the optimum angle of the knee flexors shifted (P < 0.05) to a longer muscle length by 10° after training, without significant differences between SS and PNF. No significant changes in these variables were evident for the control group. Compared with the control group, the SS and PNF groups showed significantly (P < 0.05) smaller decreases and faster recovery of knee flexor muscle strength and smaller changes in optimum angle, ROM, muscle soreness, and plasma creatine kinase activity and myoglobin concentration without significant differences between the groups. The preeccentric exercise ROM or optimum angle was significantly (P < 0.05) correlated with the changes in the muscle damage markers.
  
  
  CONCLUSIONS
  These results suggest that both SS and PNF training are effective in attenuating eccentric exercise-induced muscle damage and that flexible muscles are less susceptible to the damage.
authors.affiliation: Department of Physical Education, National Chiayi University, Chiayi County, Taiwan.
authors.forename: Che-Hsiu
authors.initials: CH
authors.lastname: Chen
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
authors.forename: Hsin-Lian
authors.initials: HL
authors.lastname: Chen
authors.forename: Ming-Ju
authors.initials: MJ
authors.lastname: Lin
authors.forename: Kuo-Wei
authors.initials: KW
authors.lastname: Tseng
authors.forename: Trevor C
authors.initials: TC
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D003402:Creatine Kinase / Q000097:blood; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000293:injuries* / Q000502:physiology*; D009211:Myoglobin / Q000097:blood; D016059:Range of Motion, Articular / Q000502:physiology; D055815:Young Adult
chemical_list: D009211:Myoglobin; D003402:Creatine Kinase