• several
  • Each muscle fiber contains several hundred to several thousand tightly packed strands called myofibrils that consist of alternating filaments of the protein substances actin actin, a protein abundantly present in many cells, especially muscle cells, that significantly contributes to the cell's structure and motility. (thefreedictionary.com)
  • time
  • Ultrasound images were recorded and speckle tracking analysis was used to quantify muscle deformation and deformation rate over 3 equal time-periods during the lifting sequence (rest, mid-lift and end-lift). (diva-portal.org)
  • The means by which all types of muscles contract is thought to be generally the same, although muscles are classified as phasic, or fast twitch, and tonic, or slow twitch, to differentiate between the various lengths of time a muscle may require to move in response to stimulation. (thefreedictionary.com)