title: Elbow flexor fatigue modulates central excitability of the knee extensors.
abstract: The present study investigated the effects of exercise-induced elbow flexor fatigue on voluntary force output, electromyographic (EMG) activity and motoneurone excitability of the nonexercised knee extensor muscles. Eleven participants attended 3 testing sessions: (i) control, (ii) unilateral fatiguing elbow flexion and (iii) bilateral fatiguing elbow flexion (BiFlex). The nonfatigued knee extensor muscles were assessed with thoracic motor evoked potentials (TMEPs), maximal compound muscle action potential (Mmax), knee extensor maximal voluntary contractions (MVCs), and normalized EMG activity before and at 30 s, 3 min, and 5 min postexercise. BiFlex showed significantly lower (Δ = -18%, p = 0.03) vastus lateralis (VL) normalized EMG activity compared with the control session whereas knee extension MVC force did not show any statistical difference between the 3 conditions (p = 0.12). The TMEP·Mmax(-1) ratio measured at the VL showed a significantly higher value (Δ = +46%, p = 0.003) following BiFlex compared with the control condition at 30 s postexercise. The results suggest that the lower VL normalized EMG following BiFlex might have been due to a reduction in supraspinal motor output because spinal motoneuronal responses demonstrated substantially higher value (30 s postexercise) and peripheral excitability (compound muscle action potential) showed no change following BiFelex than control condition.
authors: a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors: Saied Jalal
authors: SJ
authors: Aboodarda
authors: a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors: David B
authors: DB
authors: Copithorne
authors: a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors: Kevin E
authors: KE
authors: Power
authors: b School of Exercise and Health Sciences, Edith Cowan University, Perth, Australia.
authors: Eric
authors: E
authors: Drinkwater
authors: a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors: David G
authors: DG
authors: Behm
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D004550:Elbow; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007717:Knee; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction; D018763:Muscle Fatigue; D053580:Muscle Strength; D009434:Neural Pathways / Q000502:physiology; D052097:Quadriceps Muscle / Q000294:innervation*; D013997:Time Factors; D055815:Young Adult
keywords: cross-over fatigue; excitabilité motoneuronale; fatigue croisée; fatigue périphérique; motoneurone excitability; peripheral fatigue; volontaire; voluntary activation