Failed excitability of spinal motoneurons induced by prolonged running exercise.
The main purpose of this study was to investigate the modulations in H-reflex and V-wave responses (spinal loop properties) induced by prolonged locomotion activities. The second purpose was to compare the development of central fatigue between continuous and intermittent running modes. Eleven males randomly performed two 90-min running exercises either continuously (CONT, first ventilatory threshold) or intermittently (INT, 150 s at a velocity 20% higher than that during CONT/30 s of recovery). Neuromuscular tests of the plantar flexors [including M-wave and H-reflex at rest and M-wave and V-wave during maximal voluntary contraction (MVC)] were performed before and 5 and 30 min after the running exercises. During MVC, the torque significantly decreased (P < 0.05) from preexercise to 5 and 30 min postexercise (-11 and -9%, respectively), as did the RMS/M ratio (-11 and -13%, respectively) and the V/M ratio (-19 and -37%, respectively) for the soleus muscle. At rest, the H/M ratio also decreased significantly (P < 0.001) from preexercise to 5 and 30 min postexercise (-61 and -55%, respectively). Last, no difference in the alteration of spinal loop properties was noted between CONT and INT. In conclusion, the results regarding H-reflex and V-wave suggest for the first time a modulation in spinal loop properties after prolonged running.
Racinais
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Faculté des Sciences du Sports, Laboratoire EA 2991, Efficience et Déficience Motrices, Université de Montpellier 1, 700 Avenue du Pic Saint Loup, 34090 Montpellier, France. contact@sebastienracinais.com
Girard
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Micallef
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Perrey
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D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D004525:Efferent Pathways / Q000502:physiology; D004576:Electromyography; D005071:Evoked Potentials / Q000502:physiology; D017079:Exercise Tolerance / Q000502:physiology*; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D010525:Peripheral Nerves / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D012420:Running / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D019415:Torque