title: Time course of changes in passive properties of the gastrocnemius muscle-tendon unit during 5 min of static stretching.
abstract: The minimum time required for Static stretching (SS) to change the passive properties of the muscle-tendon unit (MTU), as well as the association between these passive properties, remains unclear. This study investigated the time course of changes in the passive properties of gastrocnemius MTU during 5 min of SS. The subjects comprised 20 healthy males (22.0 ± 1.8 years). Passive torque as an index of MTU resistance and myotendinous junction (MTJ) displacement as an index of muscle extensibility were assessed using ultrasonography and dynamometer during 5 min of SS. Significant differences before and every 1 min during SS were determined using Scheffé's post hoc test. Relationships between passive torque and MTJ displacement for each subject were determined using Pearson's product-moment correlation coefficient. Although gradual changes in both passive torque and MTJ displacement were demonstrated over every minute, these changes became statistically significant after 2, 3, 4, and 5 min of SS compared with the values before SS. In addition, passive torque after 5 min SS was significantly lower than that after 2 min SS. Similarly, MTJ displacement after 5 min SS was significantly higher than that after 2 min SS. A strong correlation was observed between passive torque and MTJ displacement for each subject (r = -0.886 to -0.991). These results suggest that SS for more than 2 min effectively increases muscle extensibility, which in turn decreases MTU resistance.
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan. m.nakamura@ky5.ecs.kyoto-u.ac.jp
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakamura
authors.forename: Tome
authors.initials: T
authors.lastname: Ikezoe
authors.forename: Yohei
authors.initials: Y
authors.lastname: Takeno
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ichihashi
mesh_terms: D006801:Humans; D008297:Male; D052580:Muscle Stretching Exercises / Q000379:methods*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology; D013710:Tendons / Q000000981:diagnostic imaging / Q000502:physiology; D013997:Time Factors; D019415:Torque; D014463:Ultrasonography; D055815:Young Adult