Spectral analysis of muscular sound during isometric contraction of biceps brachii

C. Orizio, R. Perini, B. Diemont, M. M. Figini, A. Veicsteinas

Research output: Contribution to journalArticlepeer-review


The frequency content of muscular sound (MS), detected by placing a contact sensor transducer over the belly of the biceps brachii during 10 isometric contractions of 4 s each [10-100% of maximal voluntary contraction (MVC)] in seven sedentary men, was analyzed by the maximum entropy spectral estimation and the fast Fourier transform methods. With increasing %MVC, the power spectrum of the MS enlarges and tends to be multimodal beyond 30% MVC. Independent of the method, the mean frequency is ~ 11 Hz at the lower tasks, and then it increases up to 15 Hz at 80% MCV and to 22 Hz at 100% MVC. When the effort is increased the relative power in the 15- to 45-Hz bandwidth (range of firing rate of the motor units with fast-twitch fibers) from 20% reaches 55% of the power in the 6- to 45-Hz bandwidth (firing rate range of motor units with slow- and fast-twitch fibers). Our results obtained by the two different modeling approaches confirm the reliability of the sound signal. Moreover, it appears that from the MS the motor unit activation pattern can be retrieved.

Original languageEnglish
Pages (from-to)508-512
Number of pages5
JournalJournal of Applied Physiology
Issue number2
Publication statusPublished - 1990


  • exertion
  • motor unit activation pattern
  • recruitment

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Fingerprint Dive into the research topics of 'Spectral analysis of muscular sound during isometric contraction of biceps brachii'. Together they form a unique fingerprint.

Cite this