scholarly journals Handgrip Maximal Voluntary Isometric Contraction Does Not Correlate with Thenar Motor Unit Number Estimation

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Arun Aggarwal
Keyword(s):  
Disease Progression ◽  
Grip Strength ◽  
Motor Unit ◽  
Isometric Contraction ◽  
Motor Units ◽  
Muscle Twitch ◽  
Maximal Voluntary Isometric Contraction ◽  
Motor Unit Number Estimation ◽  
Motor Neurones ◽  
Electrophysiological Technique

In slowly progressive conditions, such as motor neurone disease (MND), 50–80% of motor units may be lost before weakness becomes clinically apparent. Despite this, maximal voluntary isometric contraction (MVIC) has been reported as a clinically useful, reliable, and reproducible measure for monitoring disease progression in MND. We performed a study on a group of asymptomatic subjects that showed a lack of correlation between isometric grip strength and thenar MUNE. Motor unit number estimation (MUNE) estimates the number of functioning lower motor neurones innervating a muscle or a group of muscles. We used the statistical electrophysiological technique of MUNE to estimate the number of motor units in thenar group of muscles in 69 subjects: 19 asymptomatic Cu, Zn superoxide dismutase 1 (SOD 1) mutation carriers, 34 family controls, and 16 population controls. The Jamar hand dynamometer was used to measure isometric grip strength. This study suggests that MUNE is more sensitive for monitoring disease progression than maximal voluntary isometric contraction (MVIC), as MUNE correlates with the number of functional motor neurones. This supports the observation that patients with substantial chronic denervation can maintain normal muscle twitch tension until 50–80% of motor units are lost and weakness is detectable.

scholarly journals Reliability of Motor Unit Behavior during a Maximal Voluntary Isometric Contraction of the Knee Extensors

2019 ◽  
Vol 51 (Supplement) ◽  
pp. 340-341
Author(s):  
Ryan J. Colquhoun ◽  
Patrick M. Tomko ◽  
Mitchel A. Magrini ◽  
Sydnie R. Fleming ◽  
Matthew C. Ferrell ◽  
...  
Keyword(s):  
Motor Unit ◽  
Isometric Contraction ◽  
Knee Extensors ◽  
Maximal Voluntary Isometric Contraction

Monitoring disease progression using high-density motor unit number estimation in amyotrophic lateral sclerosis

2010 ◽  
Vol 42 (2) ◽  
pp. 239-244 ◽  
Author(s):  
Johannes P. van Dijk ◽  
Helenius J. Schelhaas ◽  
Ivo N. Van Schaik ◽  
Henny M.H.A. Janssen ◽  
Dick F. Stegeman ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Disease Progression ◽  
Motor Unit ◽  
High Density ◽  
Motor Unit Number Estimation ◽  
Lateral Sclerosis

scholarly journals Improved motor unit number estimate when motor unit alternation is addressed

2018 ◽  
Vol 125 (4) ◽  
pp. 1131-1140 ◽  
Author(s):  
Bradley A. DeForest ◽  
Jeffrey Winslow ◽  
Christine K. Thomas
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Multiple Point ◽  
Digital Subtraction ◽  
Motoneuron Survival ◽  
Incremental Method ◽  
Motor Unit Number Estimation ◽  
Cord Injury ◽  
Motor Unit Number Estimate ◽  
First Time

Motor unit number estimation (MUNE) is important for determining motoneuron survival with age or in conditions such as amyotrophic lateral sclerosis or spinal cord injury. The original incremental method and approaches that were introduced to minimize alternation (e.g., multiple-point stimulation) are most commonly used, but one must accept the limitation that alternation of motor units may still inflate the estimate. Alternation occurs because axon thresholds are probabilistic and overlap for different axons; therefore, different combination of motor units may respond at a given stimulus intensity. Our aims were to quantify motor unit alternation systematically in the thenar muscles of 35 healthy adults by digital subtraction of EMG and force, and to compare MUNE with and without alternation. Alternation was prevalent, with one to nine occurrences in the first 7 to 11 steps in EMG in 34 of 35 muscles. It occurred in the first 3 steps in EMG in 49% of muscles. This alternation resulted in fewer units than steps in EMG (3 to 10 units at step 7 to 11). Accounting for alternation using digital subtraction reduced MUNE by up to 50%, day-to-day, and between-participant variability in MUNE. These results highlight the need to quantify alternation to improve the reliability and precision of motor unit number estimates, which will allow for detection of smaller changes in motoneuron survival with age, various health conditions, and/or due to an intervention. NEW & NOTEWORTHY Motor unit alternation was quantified systematically for the first time, addressing a major limitation of motor unit number estimates. Accounting for alternation decreased motor unit number estimates, and improved the reliability and precision of the motor unit number estimate, which will allow smaller, clinically relevant changes in motoneuron survival to be detected.

scholarly journals Motor Unit Number Estimation in Evaluating Disease Progression in Patients with Amyotrophic Lateral Sclerosis

2010 ◽  
Vol 25 (9) ◽  
pp. 1359 ◽  
Author(s):  
Suk-Won Ahn ◽  
Su-Hyun Kim ◽  
Dong-Hoon Oh ◽  
Sung-Min Kim ◽  
Kyung Seok Park ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Disease Progression ◽  
Motor Unit ◽  
Motor Unit Number Estimation ◽  
Lateral Sclerosis

scholarly journals INTRINSIC MOTOR NEURONE EXCITABILITY IS REDUCED IN SOLEUS AND TIBIALIS ANTERIOR OF OLDER ADULTS

2021 ◽  
Author(s):  
Lucas B R Orssatto ◽  
David N Borg ◽  
Anthony J Blazevich ◽  
Raphael L Sakugawa ◽  
Anthony J Shield ◽  
...  
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Motor Unit ◽  
Tibialis Anterior ◽  
Motor Units ◽  
Motor Neurone ◽  
Age Related ◽  
Inward Currents ◽  
Motor Neurones ◽  
Intrinsic Motor

Age-related deterioration within both motor neurones and monoaminergic systems should theoretically reduce neuromodulation by weakening motor neuronal persistent inward current (PIC) strength. However, this assumption remains untested. Surface electromyographic signals were collected using two 32-channel electrode matrices placed on soleus and tibialis anterior of 25 older adults (70±4years) and 17 young adults (29±5 years) to investigate motor unit discharge behaviours. Participants performed triangular-shaped plantar and dorsiflexion contractions to 20% of maximum torque at a rise-decline rate of 2%/s of each participant's maximal torque. Pairwise and composite paired-motor unit analyses were adopted to calculate delta frequency (ΔF) and estimate PIC amplitudes. ΔF has been used to differentiate between the effects of synaptic excitation and intrinsic motor neuronal properties and is assumed to be proportional to PIC amplitude. The results show that soleus and tibialis anterior motor units in older adults had lower ΔFs when calculated with the pairwise (-0.99 and -1.29 pps, respectively) or composite (-1.65 and -2.26 pps, respectively) methods. Older adults' motor units discharged at lower rates (-2.14 and -2.03 pps, respectively) and were recruited at lower torque levels (-1.50 and -2.06% of maximum, respectively) than young adults. These results demonstrate reduced intrinsic motor neurone excitability during low-force contractions in older adults, likely mediated by decreases in the strength of persistent inward currents. Our findings might be explained by deterioration in the motor neurones or monoaminergic systems, and could contribute to the decline in motor function during ageing; these assumptions should be explicitly tested in future investigations.

Following disease progression in motor neuron disorders with 3 motor unit number estimation methods

2018 ◽  
Vol 59 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Anna Bystrup Jacobsen ◽  
Hugh Bostock ◽  
Hatice Tankisi
Keyword(s):  
Motor Neuron ◽  
Disease Progression ◽  
Motor Unit ◽  
Estimation Methods ◽  
Motor Unit Number Estimation

Human motor-unit recruitment during isometric contractions and repeated dynamic movements

1987 ◽  
Vol 57 (1) ◽  
pp. 311-324 ◽  
Author(s):  
C. K. Thomas ◽  
B. H. Ross ◽  
B. Calancie
Keyword(s):  
Motor Unit ◽  
Isometric Contraction ◽  
Rank Order ◽  
Human Subjects ◽  
Motor Units ◽  
Motor Unit Recruitment ◽  
Isometric Contractions ◽  
Abductor Pollicis Brevis ◽  
Contraction Times ◽  
Abductor Pollicis Brevis Muscle

Spike-triggered averaging was used to determine the twitch tensions and contraction times of motor units in the abductor pollicis brevis muscle of two human subjects for two directions of isometric contraction: abduction and opposition of the thumb. During isometric contractions in each direction, the threshold force for motor-unit recruitment and the twitch amplitude were correlated linearly. These data suggested that an orderly pattern of recruitment, according to increasing twitch size, describes the function of the human abductor pollicis brevis muscle for each contraction direction. Rank order of motor-unit recruitment in each isometric contraction direction was correlated, but not identical. All units contributed tension in each direction of contraction, so no clear evidence was found for task-dependent motor units. In two subjects, motor-unit recruitment order during isometric contraction of the first dorsal interosseous and abductor pollicis brevis muscles was then compared with that of motor-unit pairs in both muscles during repetitive dynamic movements. Recruitment according to increasing twitch size was largely preserved during the repetitive opening and closing of scissors. The recruitment reversals that were observed were usually between pairs of units with similar thresholds.

scholarly journals Effects of Prednisone on a Patient with Dysferlinopathy Assessed by Maximal Voluntary Isometric Contraction: Alternate-Day Low-Dose Administration for a 17-Year Period

2019 ◽  
Vol 11 (1) ◽  
pp. 10-16
Author(s):  
Keiichi Takahashi
Keyword(s):  
Grip Strength ◽  
Isometric Contraction ◽  
Low Dose ◽  
Strain Gauges ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Maximal Voluntary Isometric Contraction ◽  
Dose Administration ◽  
Beneficial Effects ◽  
Dose Prednisone

Glucocorticoids are candidates for the pharmacological treatment of dysferlinopathy. Deflazacort, however, showed a worse effect on muscle strength than placebo. Alternate-day low-dose prednisone may have beneficial effects with fewer adverse effects. The outcomes for a female patient with dysferlinopathy (limb-girdle muscular dystrophy type 2B) were assessed by maximal voluntary isometric contraction (MVIC) using a newly devised chair and arm table with push-pull type strain gauges. Grip strength was also measured isometrically. Prednisone 15 mg was started orally at the age of 24 years and was taken every other day in the morning until 41 years of age. The MVIC of flexion of the knees and elbows increased gradually and significantly. The MVIC of extension of the knees and elbows increased to a lesser extent. Isometric grip strength showed no remarkable increase, but strength was sustained over 10 years. Muscle fiber types account for these differences. The beneficial effects of alternate-day prednisone treatment on dysferlinopathy are reported.

scholarly journals Rotation of Motoneurons During Prolonged Isometric Contractions in Humans

2006 ◽  
Vol 96 (3) ◽  
pp. 1135-1140 ◽  
Author(s):  
Parveen Bawa ◽  
Marco Y. Pang ◽  
Kari A. Olesen ◽  
Blair Calancie
Keyword(s):  
Motor Unit ◽  
Isometric Contraction ◽  
Motor Units ◽  
Surface Emg ◽  
Neuromuscular Fatigue ◽  
Isometric Contractions ◽  
Muscle Type ◽  
Rotation Surface ◽  
Metabolic Recovery ◽  
The Subject

Prolonged and weak isometric contractions can result in neuromuscular fatigue. Alternation of discharge of motor units with similar thresholds (termed rotation) could be useful to minimize neuromuscular fatigue by providing periods for metabolic recovery of the contractile elements. In the present study, we investigated the prevalence of motoneuron rotation during prolonged contractions of distal limb muscles. Electromyographic (EMG; needle and surface) was recorded from muscles of the forearm and distal leg. The subject made a slowly increasing isometric contraction to recruit and discharge a motor unit ( 1) for a prolonged period of time (>30 min). Sometimes an additional motor unit ( 2) was recruited in which case the subject relaxed the contraction slightly so that only one motor unit remained tonic. Often it was this newly recruited motor unit (i.e., unit 2) that continued discharging, while motor unit 1 fell silent. Continued contraction would then lead to the resumption of tonic discharge of unit 1 and silence of unit 2. This would complete a rotation between motor units 1 and 2. During prolonged contractions, rotation was observed in ∼80% of the motor-unit pairs examined. There was no difference in rotation incidence by muscle type. For the unit pairs showing rotation, surface EMG values were significantly higher immediately prior to rotation than after rotation had occurred. Our findings show that rotation of motor units with similar recruitment thresholds during such contractions is common in distal muscles of the arm and leg and may help offset neuromuscular fatigue.

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