The role of the muscle spindles in human masseter Sheila D. Scutter a, * , Kemal S. T urker b a University of South Australia, North Terrace, Adelaide, SA 5000, Australia b University of Adelaide, North Terrace, Adelaide, SA 5005, Australia Abstract In the limb muscles, the muscle spindles have been demonstrated to be important in the maintenance of static posture. This role is supported by the close proximity of the muscle spindles to motor units that develop small forces and are fatigue-resistant, and the greater eectiveness of the input from muscle spindle aerents onto the small motoneurons supplying these motor units. In masseter, input from the muscle spindles is more eective on the larger motoneurons. This suggests that the muscle spindles may be more important in masseter for the development of large, fast forces, rather than for the maintenance of static postures. Thus muscle spindles in masseter may be important in load compensation during chewing and for the development of powerful bite forces in aggressive or defensive situations. Ó 2001 Elsevier Science B.V. All rights reserved. PsycINFO classi®cation: 2330 Keywords: Mastication; Masseter; H-re¯ex; Muscle spindles To understand the complex movements of the jaw involved in chewing and speech, and to enable symptoms of masticatory dysfunction to be treated www.elsevier.com/locate/humov Human Movement Science 20 2001) 489±497 * Corresponding author. Tel.: +61-8-83022586; fax: +61-8-83022766. E-mail address: sheila.scutter@unisa.edu.au S.D. Scutter). 0167-9457/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0167-945701)00064-1