Muscle spindle signals combine with the sense of effort to indicate limb position

Abstract

Experiments were carried out to test the hypothesis that, in the absence of vision, position sense at the human forearm is generated by the combined input from muscle spindles in elbow flexor muscles and signals of central origin giving rise to a sense of effort. In a forearm position-matching task, to remove a possible contribution from the sense of effort, the reference arm was held supported at the test angle. Subjects were less accurate in matching elbow position of the supported forearm than when it was unsupported. Adding a 2 kg weight to the unsupported reference arm led subjects to make matching errors consistent with an increase in the effort signal. Evidence of a contribution from muscle spindles was provided by showing that the direction of position matching errors could be systematically altered by flexion or extension conditioning of the reference arm before its placement at the test angle. Such changes in errors with conditioning could be shown to be present when the reference arm was supported, unsupported, or unsupported and weighted. It is concluded that both peripheral signals from muscle spindles and signals of central origin, associated with the motor command required to maintain arm position against the force of gravity, can provide information about forearm position.

Effect of eccentric exercise on position sense at the human forearm in different postures

“…We have recently provided evidence in support of a contributory role from the sense of effort to limb position sense (1,20,25). The idea that central command signals associated with the sense of effort are able to contribute to kinesthesia is not new (19).…”

“…The subject was asked to move the matching arm to the same angle. The movement of the reference arm from full extension to the test angle was likely to condition its elbow flexors, leading the matching arm to adopt a more extended position (25).…”

Effects of muscle action type on corticospinal excitability and triceps surae muscle-tendon mechanics

“…Thus, muscle spindles can be used by the CNS to sense relative positions of the body segments. (Winter et al 2005) Each spindle has three main components: (1) a group of specialized intrafusal muscle fibers whose central regions are noncontractile; (2) large-diameter myelinated sensory endings that originate from the central regions of the intrafusal fibers; and (3) small-diameter myelinated motor endings that innervate the polar contractile regions of the intrafusal fibers ( Figure 5). Because muscle spindles are arranged in parallel with the extrafusal muscle fibers that make up the main body of the muscle, the intrafusal fibers change in length as the whole muscle changes.…”

Kinezyolojik Bantlama Tekniği ve Uygulama Alanları

“…Buna karşın kinezyolojik bant ve elastik olmayan teybin, dizde 29°, 39° ve 49° fleksiyon açısını tekrar oluşturma yetisine bakan bir başka çalışmada kinezyolojik bandın 39°, klasik teybin ise daha düşük açılarda daha anlamlı gelişmeler sağladığı ortaya konmuştur (8). Kinezyolojik bant, deri ve kastaki uygulamada deri ve yüzeyel fasyanın boyunu ve kas liflerinin gerilimini değiştirerek gerilim, yüklenme, basınç ve yırtma kuvvetlerine duyarlı mekanoreseptörleri etkiler (30,31). Bu durum kasın hareket ve tonusunda belirgin değişimlere yol açabilir.…”