Change search
ReferencesLink to record
Permanent link

Direct link
Effects of cutaneous afferent input on fatigue-induced changes in fusimotor activity of decerebrate cats
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
Show others and affiliations
1997 (English)In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 79, no 3, 935-942 p.Article in journal (Refereed) Published
Abstract [en]

Interaction of cutaneous and small-diameter, primarily fatigue-induced, muscle afferent inputs on fusimotor neurons has been studied in decerebrate cats. Spike discharges of fusimotor neurons to medial gastrocnemius were recorded from filaments dissected free from this muscle nerve. Non-noxious mechanical stimuli (10 Hz, 2 mm vibration) were applied to the skin area on the lateral side of the heel, innervated by sural nerve, during long-lasting (250 s) fatiguing contraction of lateral gastrocnemius and soleus muscles, elicited by electrical stimulation (40 Hz, 1.3 x motor threshold) of the muscle nerves. In 15 units (58%) the pattern of responses to muscle contraction and/or fatigue (initial transient, and late long-lasting increase in firing rate, respectively) was preserved in the presence of skin vibration which, by itself, provoked either a slight increase or no changes in fusimotor discharge rate. Pattern of the response to skin vibration prevailed in the presence of muscle contraction and fatigue only if the vibration by itself induced marked increase in fusimotor discharge rate (three units). In the remaining eight units the responses to both stimuli applied simultaneously were dissimilar in pattern to the response to either stimulus applied alone: the initial, tension-related, increase in firing rate was prolonged, while the late, fatigue-induced one was attenuated and its post-contraction part almost abolished. Possible mechanisms and functional role of interaction between cutaneous and muscle afferent inflows are discussed.

Place, publisher, year, edition, pages
1997. Vol. 79, no 3, 935-942 p.
Keyword [en]
muscle fatigue, fusimotor neurons, cutaneous afferents
National Category
Medical and Health Sciences
URN: urn:nbn:se:umu:diva-4152DOI: 10.1016/S0306-4522(97)00039-0PubMedID: 9219956OAI: diva2:143134
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2010-06-29Bibliographically approved
In thesis
1. Experimental studies of spinal mechanisms associated with muscle fatigue
Open this publication in new window or tab >>Experimental studies of spinal mechanisms associated with muscle fatigue
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Muscle fatigue is ubiquitous in every day life.Muscle fatigue might be considered as an altered state of motor behaviour, which impairs motor performance. By contrast, muscle fatigue could also be considered a positive phenomenon, which protects muscle tissue from damage that might be incurred to it by overuse.

The principal aim of the thesis was to explore some of the mechanisms of muscle fatigue at the spinal level in animal models.The activation of multiple motor units of a single calf muscle may influence contractile properties of its neighbouring, otherwise inactive units, providing evidence for spatial spreading of fatigue between different muscle parts. The release of metabolites, their action on inactive muscle units and the effects of local hypoxia are the most likely causes. Fatigue-induced metabolite shift in the interstitium provokes excitation and/or sensitisation of high-threshold afferent fibers, with complex effects on the spinal premotoneuronal network involved in the modulation of motoneuronal output. This was examined by studing the intrasegmental lamellar distribution of the lumbar spinal interneurons following fatiguing contractions of the triceps surae muscle. Furthermore, fatigue of calf muscles enhanced the activity of fusimotor neurons to these muscles irrespective of the regime of muscle activity (isometric vs. lengthening) in conditions that simulate locomotion. Altered fusimotor activity, through increased or maintained muscle spindle afferent responsiveness may be advantageous, providing support to the skeletomotor activity and enhanced information about muscle periphery to higher nervous centres. The particular effects of interneuronal network at motor input (presynaptic inhibition system) and output (recurrent inhibition system) stages were then addressed. Fatigue of triceps surae muscle induced a suppression of the monosynaptic reflex. The intensity of presynaptic inhibition increased, while the intensity of recurrent inhibition decreased. Post fatigue-evoked changes in monosynaptic reflexes and presynaptic inhibition indicate the possibility that high-threshold afferents inhibit group Ia terminals pre-synaptically, which would allow fatigue-induced signals from the muscle to reduce the relevance of proprioceptive feedback. Besides intrasegmental, intersegmental spreading of nociceptive signals was explored. Activation of sensory afferents from dorsal neck muscles by capsaicin induces powerful activation of interneurons located in the cervical spinal cord, as well as a widespread activation of cells in lumbar spinal cord segments.

The results confirm the pivotal role of small diameter muscle afferents in the orchestration of segmental responses to fatigue and show complex interactions that may lead to limited accuracy of motor output. They also depict processes that may be related to, and even become precursors of chronic muscle pain.

Umeå University medical dissertations, ISSN 0346-6612 ; 910
muscle fatigue, monosynaptic reflex, presynaptic inhibition, recurrent inhibition, fusimotor system, Fos-immunoreactivity, referral pain
Research subject
urn:nbn:se:umu:diva-332 (URN)91-7305-703-7 (ISBN)
Public defence
2004-11-12, Stora salen, Arbetslivsinstitutet, 13:00
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2010-06-28Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Ljubisavljevic, M
By organisation
Department of Surgical and Perioperative Sciences
In the same journal
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 31 hits
ReferencesLink to record
Permanent link

Direct link