title: Acute effects of contract-relax (CR) stretch versus a modified CR technique.
abstract: OBJECTIVE
  Contract-relax (CR) stretching increases range of motion (ROM) substantively, however its use in athletic environments is limited as the contractions performed in a highly stretched position require partner assistance, are often painful, and may induce muscle damage. Therefore, the acute effects of performing the contractions 'off stretch' in the anatomical position [stretch-return-contract (SRC)] were compared with traditional CR stretching in 14 healthy human volunteers.
  
  
  METHODS
  Passive ankle joint moment and dorsiflexion ROM were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae, whilst simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. The subjects then performed CR or SRC stretches (4 × 10-s stretches and 5-s contractions) randomly on separate days before reassessment.
  
  
  RESULTS
  Significant increases in dorsiflexion ROM (4.1°-4.0°; P < 0.01) and peak passive moment (10.9-15.1%; P < 0.05) and decreases in the slope of the passive moment curve (19.1-13.3%; P < 0.05), muscle stiffness (21.7-21.3%; P < 0.01) and tendon stiffness (20.4-15.7%; P < 0.01) were observed in CR and SRC, respectively. No between-condition differences were found in any measure (P > 0.05).
  
  
  CONCLUSIONS
  Similar mechanical and neurological changes were observed between conditions, indicating that identical mechanisms underpin the ROM improvements. These data have important practical implications for the use of this stretching mode in athletic environments as performing the contractions 'off stretch' eliminates the pain response, reduces the risk of inducing muscle damage, and removes the need for partner assistance. Thus, it represents an equally effective, simpler, and yet potentially safer, stretching paradigm.
authors.affiliation: Sport, Exercise and Life Sciences, The University of Northampton, Boughton Green Road, Northampton, NN2 7AL, UK. tony.kay@northampton.ac.uk.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Kay
authors.affiliation: Sport, Exercise and Life Sciences, The University of Northampton, Boughton Green Road, Northampton, NN2 7AL, UK.
authors.forename: Steven
authors.initials: S
authors.lastname: Dods
authors.affiliation: Centre for Exercise and Sport Science Research (CESSR), School of Exercise and Health Sciences, Edith Cowan University, Joondalup, Australia.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Blazevich
mesh_terms: D000293:Adolescent; D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D015444:Exercise; D005081:Exercise Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009126:Muscle Relaxation; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular
keywords: Proprioceptive neuromuscular facilitation; Range of motion; Tendon stiffness; Ultrasound