Biomechanical Responses to Repeated Stretches in Human Hamstring Muscle In Vivo

• Published in: The American journal of sports medicine 1996-09, Vol.24 (5), p.622-628
• Main Authors: Magnusson, S. Peter, Simonsen, Erik B., Aagaard, Per, Kjaer, Michael
• Format: Article
• Language: English
• Subjects: Adult; Analysis of Variance; Area Under Curve; Biological and medical sciences; Biomechanical Phenomena; Follow-Up Studies; Fundamental and applied biological sciences. Psychology; Humans; Joints; Kinetics; Knee Joint - physiology; Leg - physiology; Legs; Male; Measurement; Muscle contraction; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Muscular system; Physiological aspects; Pliability; Range of motion; Range of Motion, Articular; Signal Processing, Computer-Assisted; Space life sciences; Sports medicine; Stress, Mechanical; Stretch (Physiology); Stretching (Physiology); Torque; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports
• ISSN: 0363-5465; 1552-3365
• DOI: 10.1177/036354659602400510

To examine stiffness, energy, and passive torque in the dynamic and static phases of a stretch maneuver in the human hamstring muscle in vivo we used a test- retest protocol and a repeated stretches protocol. Re sistance to stretch was defined as passive torque (in newton-meters) offered by the hamstring muscle group during passive knee extension as measured using an isokinetic dynamometer with a modified thigh pad. In 13 uninjured subjects, the knee was passively ex tended to a predetermined final position (0.0875 rad/ sec, dynamic phase) where it remained stationary for 90 seconds (static phase). The test-retest protocol in cluded two tests administered 1 hour apart. On a sep arate occasion, five consecutive static stretches were administered separated by 30 seconds and followed by a sixth stretch 1 hour later. For the test-retest phase, stiffness and energy in the dynamic phase and passive torque in the static phase did not differ and yielded correlations of r = 0.91 to 0.99. During the static phase, passive torque declined in both tests ( P < 0.0001). For the repeated stretches, decreases were observed for energy ( P < 0.01) and stiffness ( P < 0.05) in the dynamic phase and for passive torque ( P < 0.0001) in the static phase. However, the decline in the variables returned to baseline within 1 hour. The data show that the method employed is a useful tool for measuring biomechanical variables during a stretch maneuver. This may provide a more detailed method to examine skeletal muscle flexibility.