scholarly journals Motor unit recruitment patterns 2: the influence of myoelectric intensity and muscle fascicle strain rate

2008 ◽  
Vol 211 (12) ◽  
pp. 1893-1902 ◽  
Author(s):  
E. F. Hodson-Tole ◽  
J. M. Wakeling
Keyword(s):  
Strain Rate ◽  
Motor Unit ◽  
Motor Unit Recruitment ◽  
Muscle Fascicle ◽  
Recruitment Patterns

Change in Muscle Fascicle Length Influences the Recruitment and Discharge Rate of Motor Units During Isometric Contractions

2005 ◽  
Vol 94 (5) ◽  
pp. 3126-3133 ◽  
Author(s):  
Benjamin Pasquet ◽  
Alain Carpentier ◽  
Jacques Duchateau
Keyword(s):  
Motor Unit ◽  
Ankle Joint ◽  
Discharge Rate ◽  
Motor Units ◽  
Motor Unit Recruitment ◽  
Isometric Contractions ◽  
Neutral Position ◽  
Proprioceptive Information ◽  
Fascicle Length ◽  
Muscle Fascicle

This study examines the effect of fascicle length change on motor-unit recruitment and discharge rate in the human tibialis anterior (TA) during isometric contractions of various intensities. The torque produced during dorsiflexion and the surface and intramuscular electromyograms (EMGs) from the TA were recorded in eight subjects. The behavior of the same motor unit ( n = 59) was compared at two ankle joint angles (+10 and −10° around the ankle neutral position). Muscle fascicle length of the TA was measured noninvasively using ultrasonography recordings. When the ankle angle was moved from 10° plantarflexion to 10° dorsiflexion, the torque produced during maximal voluntary contraction (MVC) was significantly reduced [35.2 ± 3.3 vs. 44.3 ± 4.2 (SD) Nm; P < 0.001] and the average surface EMG increased (0.47 ± 0.08 vs. 0.43 ± 0.06 mV; P < 0.05). At reduced ankle joint angle, muscle fascicle length declined by 12.7% ( P < 0.01) at rest and by 18.9% ( P < 0.001) during MVC. Motor units were activated at a lower recruitment threshold for short compared with long muscle fascicle length, either when expressed in absolute values (2.1 ± 2.5 vs. 3.6 ± 3.7 Nm; P < 0.001) or relative to their respective MVC (5.2 ± 6.1 vs. 8.8 ± 9.0%). Higher discharge rate and additional motor-unit recruitment were observed at a given absolute or relative torque when muscle fascicles were shortened. However, the data indicate that increased rate coding was mainly present at low torque level (<10% MVC), when the muscle-tendon complex was compliant, whereas recruitment of additional motor units played a dominant role at higher torque level and decreased compliance (10–35% MVC). Taken together, the results suggest that the central command is modulated by the afferent proprioceptive information during submaximal contractions performed at different muscle fascicle lengths.

scholarly journals Muscle fibre recruitment can respond to the mechanics of the muscle contraction

2006 ◽  
Vol 3 (9) ◽  
pp. 533-544 ◽  
Author(s):  
James M Wakeling ◽  
Katrin Uehli ◽  
Antra I Rozitis
Keyword(s):  
Motor Unit ◽  
Muscle Activity ◽  
The Body ◽  
Motor Unit Recruitment ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Muscle Fibres ◽  
Strain Rates ◽  
Lower Velocity ◽  
Muscle Fascicle

This study investigates the motor unit recruitment patterns between and within muscles of the triceps surae during cycling on a stationary ergometer at a range of pedal speeds and resistances. Muscle activity was measured from the soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) using surface electromyography (EMG) and quantified using wavelet and principal component analysis. Muscle fascicle strain rates were quantified using ultrasonography, and the muscle–tendon unit lengths were calculated from the segmental kinematics. The EMG intensities showed that the body uses the SOL relatively more for the higher-force, lower-velocity contractions than the MG and LG. The EMG spectra showed a shift to higher frequencies at faster muscle fascicle strain rates for MG: these shifts were independent of the level of muscle activity, the locomotor load and the muscle fascicle strain. These results indicated that a selective recruitment of the faster motor units occurred within the MG muscle in response to the increasing muscle fascicle strain rates. This preferential recruitment of the faster fibres for the faster tasks indicates that in some circumstances motor unit recruitment during locomotion can match the contractile properties of the muscle fibres to the mechanical demands of the contraction.

Motor Unit Recruitment Patterns

2016 ◽  
Vol 48 ◽  
pp. 113
Author(s):  
Axel J. Knicker ◽  
Tobias Alt ◽  
Steven Lindley ◽  
Heiko K. Strueder
Keyword(s):  
Motor Unit ◽  
Motor Unit Recruitment ◽  
Recruitment Patterns

scholarly journals Quantitative T 2 ‐mapping magnetic resonance imaging for assessment of muscle motor unit recruitment patterns

2021 ◽  
Author(s):  
Erin C. Argentieri ◽  
Ek Tsoon Tan ◽  
Jeremy S. Whang ◽  
Sophie C. Queler ◽  
Joseph H. Feinberg ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Motor Unit ◽  
Motor Unit Recruitment ◽  
Resonance Imaging ◽  
Recruitment Patterns
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