Change search
ReferencesLink to record
Permanent link

Direct link
Fatigue-related depression of the feline monosynaptic gastrocnemius-soleus reflex
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
Department of Movement Physiology, Bogomoletz Institute of Physiology, National Academy of Sciences, Kiev, Ukraine.
Department of Movement Physiology, Bogomoletz Institute of Physiology, National Academy of Sciences, Kiev, Ukraine.
Department of Movement Physiology, Bogomoletz Institute of Physiology, National Academy of Sciences, Kiev, Ukraine.
Show others and affiliations
2004 (English)In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 556, no 1, 293-296 p.Article in journal (Refereed) Published
Abstract [en]

In decerebrate cats, changes in the monosynaptic reflex (MSR) of gastrocnemius-soleus (G-S) motoneurones were studied after fatiguing stimulation (FST) of the G-S muscles. Monosynaptic reflexes were evoked by stimulation of Ia fibres in the G-S nerve and recorded from a filament of ventral root (VR) L7. FST (intermittent 40 s(-1) stimulation for 10-12 min) was applied to the distal part of the cut VR S1. FST reduced MSR amplitudes to 0.64 +/- 0.04 (mean +/-s.e.m.) of the prefatigue values. The suppression remained stable for approximately 25 min and then MSR amplitudes gradually returned towards the normal. To test for the involvement of presynaptic and recurrent inhibition, MSRs were conditioned by stimulation of the nerve to the posterior biceps and semitendinosus (PBSt) muscles or a filament of VR L7, respectively. The intensity of presynaptic inhibition (reduction of the normalized value of MSR amplitude during conditioning) increased from 0.19 +/- 0.02 in prefatigue to 0.44 +/- 0.04 within a 5.3-18.2 min interval after FST, followed by a recovery. In contrast, the intensity of recurrent inhibition first diminished from 0.23 +/- 0.02 in prefatigue to 0.15 +/- 0.01 within 15.6-30.1 min after FST and then gradually recovered. Both primary afferent depolarization and the intensity of antidromic discharges in primary afferents increased with the presynaptic inhibition intensity. These results demonstrate a fatigue-related suppression of Ia excitation of synergistic motoneurones, probably arising from the activation of group III and IV afferents. The effects could in part be due to increased presynaptic inhibition, while recurrent inhibition plays a minor role.

Place, publisher, year, edition, pages
London: Cambridge U. P. , 2004. Vol. 556, no 1, 293-296 p.
Keyword [en]
Animals, Cats, Decerebrate State, Electric Stimulation, Female, Hindlimb, Male, Muscle Fatigue/*physiology, Muscle; Skeletal/innervation/*physiology, Nerve Fibers/physiology, Neural Inhibition, Presynaptic Terminals/physiology, Reflex; Monosynaptic/*physiology, Time Factors
National Category
Medical and Health Sciences
URN: urn:nbn:se:umu:diva-4153DOI: 10.1113/jphysiol.2003.053249PubMedID: 14645451OAI: diva2:143135
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2011-03-14Bibliographically 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
Kalezic, Ivana
By organisation
Sports Medicine
In the same journal
Journal of Physiology
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: 35 hits
ReferencesLink to record
Permanent link

Direct link