Muscle activity damps the soft tissue resonance that occurs in response to pulsed and continuous vibrations

• Published in: Journal of applied physiology (1985) Vol. 93; no. 3; pp. 1093 - 1103
• Main Authors: Wakeling, James M, Nigg, Benno M, Rozitis, Antra I
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.09.2002; American Physiological Society
• Subjects: Adult; Biological and medical sciences; Electromyography; Feet; Foot; Fundamental and applied biological sciences. Psychology; Humans; Leg - physiology; Male; Models, Biological; Muscle, Skeletal - physiology; Muscular system; Physical Stimulation - methods; Resonance; Running; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Vibration; Damping; Human; Stimulus frequency; Vibration; Heel; Lower limb; Impact study; Striated muscle; Running locomotion; Foot; Soils; Soft tissue; Resonance; Mechanical stimulus; Response stimulus relation
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00142.2002

Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada T2N 1N4 This study tested the hypotheses that when the excitation frequency of mechanical stimuli to the foot was close to the natural frequency of the soft tissues of the lower extremity, the muscle activity increases 1 ) the natural frequency and 2 ) the damping to minimize resonance. Soft tissue vibrations were measured with triaxial accelerometers, and muscle activity was measured by using surface electromyography from the quadriceps, hamstrings, tibialis anterior, and triceps surae groups from 20 subjects. Subjects were presented vibrations while standing on a vibrating platform. Both continuous vibrations and pulsed bursts of vibrations were presented, across the frequency range of 10-65 Hz. Elevated muscle activity and increased damping of vibration power occurred when the frequency of the input was close to the natural frequency of each soft tissue. However, the natural frequency of the soft tissues did not change in a manner that correlated with the frequency of the input. It is suggested that soft tissue damping may be the mechanism by which resonance is minimized at heel strike during running. damping; frequency; heel strike; impact; muscle; running