title: Effects of contract-relax vs static stretching on stretch-induced strength loss and length-tension relationship.
abstract: The purpose of this study was to determine the acute effects of contract-relax stretching (CRS) vs static stretching (SS) on strength loss and the length-tension relationship. We hypothesized that there would be a greater muscle length-specific effect of CRS vs SS. Isometric hamstring strength was measured in 20 healthy people at four knee joint angles (90°, 70°, 50°, 30°) before and after stretching. One leg received SS, the contralateral received CRS. Both stretching techniques resulted in significant strength loss, which was most apparent at short muscle lengths [SS: P = 0.025; stretching × angle P < 0.001; 11.7% at 90° P < 0.01; 5.6% at 70° nonsignificant (ns); 1.3% at 50° ns; -3.7% at 30° ns. CRS: P < 0.001; stretching × angle P < 0.001; 17.7% at 90°, 13.4% at 70°, 11.4% at 50°, all P < 0.01, 4.3% at 30° ns]. The overall stretch-induced strength loss was greater (P = 0.015) after CRS (11.7%) vs SS (3.7%). The muscle length effect on strength loss was not different between CRS and SS (stretching × angle × stretching technique P = 0.43). Contrary to the hypothesis, CRS did not result in a greater shift in the length-tension relationship, and in fact, resulted in greater overall strength loss compared with SS. These results support the use of SS for stretching the hamstrings.
authors.affiliation: Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, New York, USA.|Institute of Sports Medicine Copenhagen & Musculoskeletal Rehabilitation Research Unit, Bispebjerg Hospital, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: S S
authors.initials: SS
authors.lastname: Balle
authors.affiliation: Institute of Sports Medicine Copenhagen & Musculoskeletal Rehabilitation Research Unit, Bispebjerg Hospital, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: S P
authors.initials: SP
authors.lastname: Magnusson
authors.affiliation: Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, New York, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: McHugh
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009126:Muscle Relaxation; D053580:Muscle Strength / Q000502:physiology*; D052580:Muscle Stretching Exercises / Q000009:adverse effects / Q000379:methods*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular; D013848:Thigh; D019415:Torque; D055815:Young Adult
keywords: Stretch-induced strength loss; angle-torque relationship; hamstring muscle; knee flexion