Twitch potentiation induced by two different modalities of neuromuscular electrical stimulation: Implications for motor unit recruitment

2015 ◽  
Vol 51 (3) ◽  
pp. 412-418 ◽  
Author(s):  
Sarah Regina Dias Da Silva ◽  
Daria Neyroud ◽  
Nicola A. Maffiuletti ◽  
Julien Gondin ◽  
Nicolas Place
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
Neuromuscular Electrical Stimulation ◽  
Motor Unit Recruitment ◽  
Twitch Potentiation

Interleaved neuromuscular electrical stimulation: Motor unit recruitment overlap

2017 ◽  
Vol 55 (4) ◽  
pp. 490-499 ◽  
Author(s):  
Matheus J. Wiest ◽  
Austin J. Bergquist ◽  
Helen L. Schimidt ◽  
Kelvin E. Jones ◽  
David F. Collins
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
Neuromuscular Electrical Stimulation ◽  
Motor Unit Recruitment

Motor unit recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly: quadriceps femoris

2012 ◽  
Vol 113 (1) ◽  
pp. 78-89 ◽  
Author(s):  
A. J. Bergquist ◽  
M. J. Wiest ◽  
D. F. Collins
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
Femoral Nerve ◽  
Neuromuscular Electrical Stimulation ◽  
Quadriceps Muscle ◽  
Nerve Trunk ◽  
Motor Unit Recruitment ◽  
Muscle Quality ◽  
Electromyographic Activity ◽  
Muscle Belly

Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and both can generate contractions through peripheral and central pathways. Generating contractions through peripheral pathways is associated with a nonphysiological motor unit recruitment order, which may limit the efficacy of NMES rehabilitation. Presently, we compared recruitment through peripheral and central pathways for contractions of the knee extensors evoked by NMES applied over the femoral nerve vs. the quadriceps muscle. NMES was delivered to evoke 10 and 20% of maximum voluntary isometric contraction torque 2–3 s into the NMES (time1) in two patterns: 1) constant frequency (15 Hz for 8 s); and 2) step frequency (15–100-15 Hz and 25–100-25 Hz for 3–2-3 s, respectively). Torque and electromyographic activity recorded from vastus lateralis and medialis were quantified at the beginning (time1) and end (time2; 6–7 s into the NMES) of each pattern. M-waves (peripheral pathway), H-reflexes, and asynchronous activity (central pathways) during NMES were quantified. Torque did not differ regardless of NMES location, pattern, or time. For both muscles, M-waves were ∼7–10 times smaller and H-reflexes ∼8–9 times larger during NMES over the nerve compared with over the muscle. However, unlike muscles studied previously, neither torque nor activity through central pathways were augmented following 100 Hz NMES, nor was any asynchronous activity evoked during NMES at either location. The coefficient of variation was also quantified at time2to determine the consistency of each dependent measure between three consecutive contractions. Torque, M-waves, and H-reflexes were most variable during NMES over the nerve. In summary, NMES over the nerve produced contractions with the greatest recruitment through central pathways; however, considering some of the limitations of NMES over the femoral nerve, it may be considered a good complement to, as opposed to a replacement for, NMES over the quadriceps muscle for maintaining muscle quality and reducing contraction fatigue during NMES rehabilitation.

scholarly journals Modulation of motor unit activity in biceps brachii by neuromuscular electrical stimulation applied to the contralateral arm

2015 ◽  
Vol 118 (12) ◽  
pp. 1544-1552 ◽  
Author(s):  
Ioannis G. Amiridis ◽  
Diba Mani ◽  
Awad Almuklass ◽  
Boris Matkowski ◽  
Jeffrey R. Gould ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
Unit Activity ◽  
Pulse Width ◽  
Biceps Brachii ◽  
Neuromuscular Electrical Stimulation ◽  
Motor Units ◽  
Elbow Flexors ◽  
Discharge Characteristics ◽  
Low Threshold

The purpose of the study was to determine the influence of neuromuscular electrical stimulation (NMES) current intensity and pulse width applied to the right elbow flexors on the discharge characteristics of motor units in the left biceps brachii. Three NMES current intensities were applied for 5 s with either narrow (0.2 ms) or wide (1 ms) stimulus pulses: one at 80% of motor threshold and two that evoked contractions at either ∼10% or ∼20% of maximal voluntary contraction (MVC) force. The discharge times of 28 low-threshold (0.4–21.6% MVC force) and 16 high-threshold (31.7–56.3% MVC force) motor units in the short head of biceps brachii were determined before, during, and after NMES. NMES elicited two main effects: one involved transient deflections in the left-arm force at the onset and offset of NMES and the other consisted of nonuniform modulation of motor unit activity. The force deflections, which were influenced by NMES current intensity and pulse width, were observed only when low-threshold motor units were tracked. NMES did not significantly influence the discharge characteristics of tracked single-threshold motor units. However, a qualitative analysis indicated that there was an increase in the number of unique waveforms detected during and after NMES. The findings indicate that activity of motor units in the left elbow flexors can be modulated by NMES current and pulse width applied to right elbow flexors, but the effects are not distributed uniformly to the involved motor units.

Wide-pulse-high-frequency neuromuscular stimulation of triceps surae induces greater muscle fatigue compared with conventional stimulation

2014 ◽  
Vol 116 (10) ◽  
pp. 1281-1289 ◽  
Author(s):  
Daria Neyroud ◽  
David Dodd ◽  
Julien Gondin ◽  
Nicola A. Maffiuletti ◽  
Bengt Kayser ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Muscle Fatigue ◽  
Motor Unit ◽  
High Frequency ◽  
Neuromuscular Electrical Stimulation ◽  
Triceps Surae ◽  
Voluntary Activation ◽  
Activation Level ◽  
Paired Stimulation ◽  
Voluntary Activation Level

We compared the extent and origin of muscle fatigue induced by short-pulse-low-frequency [conventional (CONV)] and wide-pulse-high-frequency (WPHF) neuromuscular electrical stimulation. We expected CONV contractions to mainly originate from depolarization of axonal terminal branches (spatially determined muscle fiber recruitment) and WPHF contractions to be partly produced via a central pathway (motor unit recruitment according to size principle). Greater neuromuscular fatigue was, therefore, expected following CONV compared with WPHF. Fourteen healthy subjects underwent 20 WPHF (1 ms-100 Hz) and CONV (50 μs-25 Hz) evoked isometric triceps surae contractions (work/rest periods 20:40 s) at an initial target of 10% of maximal voluntary contraction (MVC) force. Force-time integral of the 20 evoked contractions (FTI) was used as main index of muscle fatigue; MVC force loss was also quantified. Central and peripheral fatigue were assessed by voluntary activation level and paired stimulation amplitudes, respectively. FTI in WPHF was significantly lower than in CONV (21,717 ± 11,541 vs. 37,958 ± 9,898 N·s P<0,001). The reductions in MVC force (WPHF: −7.0 ± 2.7%; CONV: −6.2 ± 2.5%; P < 0.01) and paired stimulation amplitude (WPHF: −8.0 ± 4.0%; CONV: −7.4 ± 6.1%; P < 0.001) were similar between conditions, whereas no change was observed for voluntary activation level ( P > 0.05). Overall, our results showed a different motor unit recruitment pattern between the two neuromuscular electrical stimulation modalities with a lower FTI indicating greater muscle fatigue for WPHF, possibly limiting the presumed benefits for rehabilitation programs.

scholarly journals Physiological recruitment of motor units by high-frequency electrical stimulation of afferent pathways

2015 ◽  
Vol 118 (3) ◽  
pp. 365-376 ◽  
Author(s):  
Jakob L. Dideriksen ◽  
Silvia Muceli ◽  
Strahinja Dosen ◽  
Christopher M. Laine ◽  
Dario Farina
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
High Frequency ◽  
Muscle Activation ◽  
Motor Units ◽  
H Reflex ◽  
Motor Unit Recruitment ◽  
Afferent Stimulation ◽  
Reflex Responses ◽  
Stimulation Of

Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation, but electrically evoked muscle activation is in several ways different from voluntary muscle contractions. These differences lead to challenges in the use of NMES for restoring muscle function. We investigated the use of low-current, high-frequency nerve stimulation to activate the muscle via the spinal motoneuron (MN) pool to achieve more natural activation patterns. Using a novel stimulation protocol, the H-reflex responses to individual stimuli in a train of stimulation pulses at 100 Hz were reliably estimated with surface EMG during low-level contractions. Furthermore, single motor unit recruitment by afferent stimulation was analyzed with intramuscular EMG. The results showed that substantially elevated H-reflex responses were obtained during 100-Hz stimulation with respect to a lower stimulation frequency. Furthermore, motor unit recruitment using 100-Hz stimulation was not fully synchronized, as it occurs in classic NMES, and the discharge rates differed among motor units because each unit was activated only after a specific number of stimuli. The most likely mechanism behind these observations is the temporal summation of subthreshold excitatory postsynaptic potentials from Ia fibers to the MNs. These findings and their interpretation were also verified by a realistic simulation model of afferent stimulation of a MN population. These results suggest that the proposed stimulation strategy may allow generation of considerable levels of muscle activation by motor unit recruitment that resembles the physiological conditions.

Motor unit recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly: triceps surae

2011 ◽  
Vol 110 (3) ◽  
pp. 627-637 ◽  
Author(s):  
A. J. Bergquist ◽  
J. M. Clair ◽  
D. F. Collins
Keyword(s):  
Electrical Stimulation ◽  
Motor Unit ◽  
Tibial Nerve ◽  
Plantar Flexion ◽  
Neuromuscular Electrical Stimulation ◽  
Nerve Trunk ◽  
Triceps Surae ◽  
Size Principle ◽  
Muscle Belly ◽  
Triceps Surae Muscles

Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating motor (peripheral pathway) and sensory (central pathway) axons. In the present experiments, we compared the peripheral and central contributions to plantar flexion contractions evoked by stimulation over the tibial nerve vs. the triceps surae muscles. Generating contractions through central pathways follows Henneman's size principle, whereby low-threshold motor units are activated first, and this may have advantages for rehabilitation. Statistical analyses were performed on data from trials in which NMES was delivered to evoke 10–30% maximum voluntary torque 2–3 s into the stimulation (Time1). Two patterns of stimulation were delivered: 1) 20 Hz for 8 s; and 2) 20–100-20 Hz for 3–2-3 s. Torque and soleus electromyography were quantified at the beginning (Time1) and end (Time2; 6–7 s into the stimulation) of each stimulation train. H reflexes (central pathway) and M waves (peripheral pathway) were quantified. Motor unit activity that was not time-locked to each stimulation pulse as an M wave or H reflex (“asynchronous” activity) was also quantified as a second measure of central recruitment. Torque was not different for stimulation over the nerve or the muscle. In contrast, M waves were approximately five to six times smaller, and H reflexes were approximately two to three times larger during NMES over the nerve vs. the muscle. Asynchronous activity increased by 50% over time, regardless of the stimulation location or pattern, and was largest during NMES over the muscle belly. Compared with NMES over the triceps surae muscles, NMES over the tibial nerve produced contractions with a relatively greater central contribution, and this may help reduce muscle atrophy and fatigue when NMES is used for rehabilitation.

Motor unit control properties in constant-force isometric contractions

1996 ◽  
Vol 76 (3) ◽  
pp. 1503-1516 ◽  
Author(s):  
C. J. de Luca ◽  
P. J. Foley ◽  
Z. Erim
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Motor Units ◽  
Motor Unit Recruitment ◽  
Constant Force ◽  
Force Output ◽  
Myoelectric Signals ◽  
Firing Rates ◽  
Twitch Potentiation ◽  
Maximal Effort

1. The purpose of this study was 1) to characterize the decrease observed in mean firing rates of motor units in the first 8-15 s of isometric constant-force contractions and 2) to investigate possible mechanisms that could account for the ability to maintain force output in the presence of decreasing motor unit firing rates. 2. The decrease in mean firing rates was characterized by investigating myoelectric signals detected with a specialized quadrifilar needle electrode from the first dorsal interosseus (FDI) and the tibialis anterior (TA) muscles of 19 healthy subjects during a total of 85 constant-force isometric contractions at 30, 50, or 80% of maximal effort. The firing times of motor units were obtained from the myoelectric signals with the use of computer algorithms to decompose the signal into the constituent motor unit action potentials. Time-varying mean firing rates and recruitment thresholds were also calculated. 3. Motor units detected from the TA muscle were found to have a continual decrease in their mean firing rates in 36 of 44 trials performed during isometric ankle dorsiflexion at force values ranging from 30 to 80% of maximal effort and a duration of 8-15 s. Likewise, motor units detected in the FDI muscle displayed a decrease in firing rate in 32 of 41 trials performed during constant-force isometric index finger abduction for contractions ranging from 30 to 80% of maximal effort. In 14 contractions (16% of total), firing rates were essentially constant, whereas in 3 contractions (4%), firing rates appeared to increase. 4. Motor units with the higher recruitment thresholds and lower firing rates tended to display the greater decreases in firing rate over the constant-force interval, whereas motor units with lower recruitment thresholds and higher firing rates had lesser rates of decrease. Furthermore, increasing contraction levels tended to intensify the decrease in the motor unit firing rates. 5. Three possible mechanisms were considered as factors responsible for the maintaining of force output while motor units decreased their firing rates: motor unit recruitment, agonist/antagonist interaction, and twitch potentiation. Of these, motor unit recruitment was discarded first because none was observed during the 8-15 s duration of any of the 85 contractions. Furthermore, contractions outside the physiological range of motor unit recruitment (at 80% of maximal effort) revealed the same decreasing trend in firing rates, ruling out recruitment as the means of sustaining force output. 6. The role of agonist or antagonist muscle interaction was investigated with the use of the muscles controlling the wrist joint. Myoelectric signals were recorded with quadrifilar needle electrodes from the wrist extensor muscles while myoelectric activity in the wrist flexor muscles was concurrently monitored with surface electrodes during constant-force isometric wrist extension at 50% of maximal effort. Firing rates of the motor units in the wrist extensor muscles simultaneously decreased while the flexor muscles were determined to be inactive. 7. All the findings of this study regarding the behavior of the firing rates could be well explained by the reported characteristics of twitch potentiation that have been previously documented in animals and humans. 8. The results of this study, combined with the results of other investigators, provide the following scenario to explain how a constant-force isometric contraction is sustained. As the contraction progresses, the twitch force of the muscle fibers undergoes a potentiation followed by a decrease. Simultaneously, the "late adaptation" property of the motoneuron decreases the firing rate of the motor unit. Findings of this study suggest that voluntary reduction in firing rates also cannot be ruled out as a means to augment the adaptation in motoneurons. (ABSTRACT TRUNCATED)

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