Relationship between neuromuscular fatigue and spasticity in chronic stroke patients: a pilot study.
BACKGROUND
The aim of this study was to assess the effects of neuromuscular fatigue on stretch reflex-related torque and electromyographic activity of spastic knee extensor muscles in hemiplegic patients. The second aim was to characterize the time course of quadriceps muscle fatigue during repetitive concentric contractions.


METHODS
Eighteen patients performed passive, isometric and concentric isokinetic evaluations before and after a fatigue protocol using an isokinetic dynamometer. Voluntary strength and spasticity were evaluated following the simultaneous recording of torque and electromyographic activity of rectus femoris (RF), vastus lateralis (VL) and biceps femoris (BF).


RESULTS
Isometric knee extension torque and the root mean square (RMS) value of VL decreased in the fatigued state. During the fatigue protocol, the normalized peak torque decreased whereas the RMS of RF and BF increased between the first five and last five contractions. There was a linear decrease in the neuromuscular efficiency-repetitions relationships for RF and VL. The peak resistive torque and the normalized RMS of RF and VL during passive stretching movements were not modified by the fatigue protocol for any stretch velocity.


CONCLUSIONS
This study showed that localized quadriceps muscle fatigue caused a decrease in voluntary strength which did not modify spasticity intensity. Changes in the distribution of muscle fiber type, with a greater number of slow fibers on the paretic side, may explain why the stretch reflex was not affected by fatigue.
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France. Electronic address: julien.boudarham@rpc.aphp.fr.
Julien
J
Boudarham
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France.
Nicolas
N
Roche
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France.
Mickael
M
Teixeira
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France.
Sophie
S
Hameau
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France.
Johanna
J
Robertson
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France.
Djamel
D
Bensmail
Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France; Laboratory of Human Motricity, Sport, Education and Health (EA 6309), University of Nice Sophia Antipolis, France.
Raphael
R
Zory
D000328:Adult; D000368:Aged; D004576:Electromyography / Q000379:methods*; D005260:Female; D006429:Hemiplegia / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000502:physiology; D007719:Knee Joint / Q000502:physiology; D007866:Leg; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D009128:Muscle Spasticity / Q000503:physiopathology*; D053580:Muscle Strength; D010865:Pilot Projects; D052097:Quadriceps Muscle / Q000502:physiology*; D012026:Reflex, Stretch; D019415:Torque
Hemiplegia; Isokinetic; Quadriceps; Reflex; Strength