Motor unit discharge rate following twitch potentiation in human triceps brachii muscle.
It has been proposed that during brief voluntary contractions, twitch potentiation may sustain force output despite a decline in motor unit discharge rate. This study examined the evoked twitch force and motor unit discharge rates during submaximal voluntary contractions of the triceps brachii muscle before and after a 5 s conditioning contraction (CC) at 75% of maximal voluntary force. After the CC, twitch force potentiated ( approximately 1.3-2-fold), and the discharge rate in 33 of 35 motor units declined significantly by 1-6 Hz. The increase in twitch force was significantly correlated with the decline in discharge rate (r=-0.74). These findings suggest that the extent of the decrease in motor unit discharge rate following a CC is associated with the magnitude of twitch potentiation.
Klein
C S
CS
School of Kinesiology, The University of Western Ontario, London, Ontario, N6G 1H1, Canada.
Ivanova
T D
TD
Rice
C L
CL
Garland
S J
SJ
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D001132:Arm / Q000294:innervation / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology; D011930:Reaction Time / Q000502:physiology