Eccentric exercise alters muscle sensory motor control through the release of inflammatory mediators.
Following downhill exercise, muscle damage and local inflammatory reactions, induced by lengthening contractions, are observed and voluntary muscle activation decreases. The hypothesis that feedback carried by the group IV muscle afferents could be involved has often been raised but never measured in vivo in these conditions. In this experiment, we tested the response of the group IV muscle afferents from the lower limb to injections of KCl and lactic acid in non-exercising rats and at 1, 2, and 8 days after one running session (-13 degrees, 16 m/min). At days 1 and 2, the baseline discharge of the group IV afferents increased, but further activation by test agents was absent. After 8 days, the afferent response was equivalent to the control response. Pretreatment with betamethasone before exercise abolished the effects of downhill exercise. In non-exercising rats, arachidonic acid evoked group IV afferent discharge and suppressed their further response to another stimulus. These results demonstrate that exhaustive downhill running highly activates, for at least 2 days, the sensory feedback carried by group IV afferents through the local release of inflammatory mediators. Such an altered sensori-motor control, accompanying the post-eccentric inflammatory syndrome, could play a key role in deterioration of muscle performance and of its voluntary activation.
Marqueste
Tanguy
T
Laboratoire des Determinants Physiologiques de l'Activite Physique, Institut Fédératif de Recherches Etienne-Jules Marey, Faculté des Sciences du Sport de Marseille-Luminy, Université de la Méditerranée, 13288 Marseille cedex 09, France.
Decherchi
Patrick
P
Messan
Folly
F
Kipson
Nathalie
N
Grélot
Laurent
L
Jammes
Yves
Y
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D001623:Betamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D019054:Evoked Potentials, Motor / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D066298:In Vitro Techniques; D018836:Inflammation Mediators / Q000378:metabolism*; D019344:Lactic Acid / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010805:Physical Conditioning, Animal; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D000893:Anti-Inflammatory Agents; D018836:Inflammation Mediators; D016718:Arachidonic Acid; D019344:Lactic Acid; D011189:Potassium Chloride; D001623:Betamethasone