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

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.

SHORT-TERM SYNCHRONY OF MOTOR UNIT DISCHARGE DURING WEAK ISOMETRIC CONTRACTION IN PARKINSON'S DISEASE

Brain ◽  
1992 ◽  
Vol 115 (1) ◽  
pp. 137-154 ◽  
Author(s):  
J. R. BAKER ◽  
N. J. DAVEY ◽  
P. H. ELLAWAY ◽  
C. L. FRIEDILAND
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Motor Unit ◽  
Isometric Contraction ◽  
Short Term ◽  
Unit Discharge ◽  
Motor Unit Discharge

Cardiovascular and nitric oxide response after maximal voluntary isometric contraction in adolescents with and without Down Syndrome v1

2021 ◽  
Author(s):  
Geiziane Leite Rodrigues Melo ◽  
Dahan Cunha Nascimento ◽  
Weldson Abreu ◽  
Rafael Olher ◽  
Lysleine Deus ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Down Syndrome ◽  
Isometric Contraction ◽  
Cardiovascular Response ◽  
Exercise Session ◽  
Isometric Handgrip ◽  
Maximal Voluntary Isometric Contraction ◽  
Post Exercise ◽  
Muscle Groups ◽  
Familiarization Session

Background This study was designed to compare the cardiovascular and nitric oxide (NO) responses to maximal voluntary isometric contraction (MVIC) with different muscle groups (leg press [LEP] and isometric handgrip [IHG] exercise) of adolescents with Down syndrome (DS) and age-matched non-DS peers. We also aimed to compare the absolute and relative IHG strength between groups. MethodsEleven adolescents with DS (14.1 ± 1.0 years) and ten without DS (13.7 ± 1.25 years)participants performed two experimental sessions of LEP and IHG exercises: 1) familiarization session and 2) 3 attempts x 5-sec contraction at MVIC with 3-min rest interval. Blood pressure (BP), heart rate (HR) and NO were collected at rest, immediately post-exercise session, and 10-min post-exercise. Results There were no differences for cardiovascular and NO responses between groups for MVIC test using different muscle groups. However, DS group displayed a lower but not significantly cardiovascular response at rest and after MVIC tests than controls. Furthermore, DS group displayed a higher NO- concentration at rest, recovery and after IHG when compared to controls (P< 0.05). In addition, DS adolescents displayed a significantly lower level in absolute and relative IHG strength when compared to controls (P = 0.001). Conclusions Individuals with DS display a lower cardiovascular response at rest and after MVIC tests than controls and higher NO response after exercise.

Motor unit firing rates during constant isometric contraction: establishing and comparing an age-related pattern among muscles

2021 ◽  
Author(s):  
Eric A. Kirk ◽  
Anita D. Christie ◽  
Christopher A. Knight ◽  
Charles L. Rice
Keyword(s):  
Older Adults ◽  
Motor Unit ◽  
Isometric Contraction ◽  
Voluntary Contraction ◽  
Age Related ◽  
Motor Unit Firing ◽  
Euclidean Distances ◽  
Intramuscular Electromyography ◽  
Related Pattern ◽  
Variance Explained

Motor unit (MU) firing rate (FR) frequency is lower in aged adults, compared with young, at relative voluntary contraction intensities. However, from a variety of independent studies of disparate muscles, the age-related degree of difference in FR among muscles is unclear. Using a standardized statistical approach with data derived from primary studies, we quantified differences in FRs across several muscles between younger and older adults. The dataset included 12 different muscles in young (18-35) and older adults (62-93 years) from 18 published and one unpublished study. Experiments recorded single MU activity from intramuscular electromyography during constant isometric contraction at different (step-like) voluntary intensities. For each muscle, FR ranges and FR variance explained by voluntary contraction intensity were determined using bootstrapping. Dissimilarity of FR variance among muscles was calculated by Euclidean distances. There were 3-fold differences in the absolute frequency of FR ranges across muscles in the young (soleus 8-16 and superior trapezius 20-49 Hz), but in the old, FR ranges were more similar and lower for 9 out of 12 muscles. In contrast, the explained FR variance from voluntary contraction intensity in the older group had 1.6-fold greater dissimilarity among muscles than the young (p < 0.001), with FR variance differences being muscle dependent. Therefore, differences between muscle FR ranges were not explained by how FRs scale to changes in voluntary contraction intensity within each muscle. Instead, FRs were muscle dependent but were more dissimilar among muscles in the older group in their responsiveness to voluntary contraction intensity.

scholarly journals Changes in plasma C1q, apelin and adropin concentrations in older adults after descending and ascending stair walking intervention

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Trevor C. Chen ◽  
Tsang-Hai Huang ◽  
Wei-Chin Tseng ◽  
Kuo-Wei Tseng ◽  
Chung-Chan Hsieh ◽  
...  
Keyword(s):  
Outcome Measures ◽  
Training Session ◽  
Blood Lipid ◽  
Tolerance Test ◽  
Knee Extensors ◽  
Oral Glucose ◽  
Obese Women ◽  
Maximal Voluntary Isometric Contraction ◽  
Walking Intervention ◽  
Stair Walking

AbstractThis study compared changes in plasma complement component 1q (C1q), apelin and adropin concentrations in older obese women after descending (DSW) and ascending stair walking (ASW) training (n = 15/group) performed twice a week for 12 weeks, with gradual increases in exercise time from 5 to 60 min. Fasting blood samples were collected 3 days before the first and 4 days after the last training session. The improvements in the maximal voluntary isometric contraction (MVIC) strength of the knee extensors, functional physical fitness [e.g., 30-s chair stand (CS) performance], resting systolic blood pressure (SBP), insulin sensitivity [e.g., oral glucose tolerance test (OGTT)] and blood lipid profiles [e.g., total cholesterol (TC)] were greater (p < 0.05) in the DSW than ASW group. Plasma C1q decreased (− 51 ± 30%), and apelin (23 ± 15%) and adropin (127 ± 106%) increased (p ≤ .0.05) only after DSW. Significant (p ≤  0.01) partial correlations were found between the pre- to post-DSW changes in C1q, apelin or adropin and changes in outcome measures [e.g., C1q and MVIC (r = − 0.837), apelin and SBP (r = − 0.854), and andropin and OGTT (r = − 0.729)]. These results showed that greater decreases in plasma C1q and greater increases in apelin and adropin concentrations were associated with greater improvements in outcome measures after DSW than after ASW.

The Association of Obesity With Quadriceps Activation During Sit-to-Stand

2020 ◽  
Vol 100 (12) ◽  
pp. 2134-2143
Author(s):  
Lance M Bollinger ◽  
Amanda L Ransom
Keyword(s):  
Vastus Lateralis ◽  
Knee Extensor ◽  
Quadriceps Muscle ◽  
Knee Extensors ◽  
Emg Activity ◽  
Vastus Medialis ◽  
Trunk Flexion ◽  
Maximal Voluntary Isometric Contraction ◽  
Sit To Stand ◽  
The Mean

Abstract Objective Obesity reduces voluntary recruitment of quadriceps during single-joint exercises, but the effects of obesity on quadriceps femoris muscle activation during dynamic daily living tasks, such as sit-to-stand (STS), are largely unknown. The purpose of this study was to determine how obesity affects quadriceps muscle recruitment during STS. Methods In this cross-sectional study, 10 women who were lean and 17 women who were obese completed STS from a chair with arms crossed over the chest. Three-dimensional motion analysis was used to define 3 distinct phases (I–III) of the STS cycle. The electromyographic (EMG) activity of the vastus medialis, vastus lateralis, and semitendinosus was measured. Results STS duration was greater (3.02 [SD = 0.75] seconds vs 1.67 [SD = 0.28] seconds) and peak trunk flexion angle was lower (28.9 degrees [SD = 10.4 degrees] vs 35.8 degrees [SD = 10.1 degrees]) in the women who were obese than in the women who were lean. The mean EMG activity of the knee extensors increased from phase I to phase II in both groups; however, the mean EMG activities of both the vastus medialis (32.1% [SD = 16.6%] vs 47.3% [SD = 19.6%] maximal voluntary isometric contraction) and the vastus lateralis (31.8% [SD = 19.4%] vs 47.5% [SD = 19.6%] maximal voluntary isometric contraction) were significantly lower during phase II in the women who were obese. The mean EMG activity of the semitendinosus increased throughout STS but was not significantly different between the 2 groups. Coactivation of the semitendinosus and knee extensors tended to be greater in the women who were obese but failed to reach statistical significance. Conclusions Knee extensor EMG amplitude was reduced in women who were obese during STS, despite reduced trunk flexion. Impact Reduced knee extensor recruitment during STS in obesity may redistribute forces needed to complete this task to other joints. Functional movement training may help improve knee extensor recruitment during STS in people who are obese. Lay Summary People with obesity often have low quadriceps muscle strength and impaired mobility during daily activities. This study shows that women who are obese have lower voluntary recruitment of quadriceps when rising from a chair than women who are lean do, which could increase workload on hip or ankle muscles during this important daily task. Quadriceps strengthening exercises might improve the ability to rise from sitting to standing.

Simultaneous potentiation and fatigue in quadriceps after a 60-second maximal voluntary isometric contraction

1991 ◽  
Vol 70 (2) ◽  
pp. 726-731 ◽  
Author(s):  
R. W. Grange ◽  
M. E. Houston
Keyword(s):  
Isometric Contraction ◽  
Recovery Period ◽  
Lactate Concentration ◽  
Fold Increase ◽  
Quadriceps Muscle ◽  
Muscle Performance ◽  
Light Chains ◽  
Maximal Voluntary Isometric Contraction ◽  
Muscle Lactate ◽  
Isometric Twitch

Potential mechanisms of fatigue (metabolic factors) and potentiation (phosphate incorporation by myosin phosphorylatable light chains) were investigated during recovery from a 60-s maximal voluntary isometric contraction (MVC) in the quadriceps muscle of 12 subjects. On separate days before and for 2 h after the 60-s MVC, either a 1-s MVC or electrically stimulated contractions were used as indexes to test muscle performance. Torque at the end of the 60-s MVC was 57% of the initial level, whereas torques from a 1-s MVC and 50-Hz stimulation were most depressed in the immediate recovery period. At this time, muscle biopsy analyses revealed significant decreases in ATP and phosphocreatine and a 19-fold increase in muscle lactate. Conversely, isometric twitch torque and torque from a 10-Hz stimulus were the least depressed of six contractile indexes and demonstrated potentiation of 25 and 34%, respectively, by 4 min of recovery (P less than 0.05). At this time, muscle lactate concentration was still 16 times greater than at rest. An increased phosphate content of the myosin phosphorylatable light chains (P less than 0.05) was also evident both immediately and 4 min after the 60-s MVC. We conclude that the 60-s MVC produced marked force decreases likely due to metabolic displacement, while the limited decline in the twitch and 10-Hz torques and their significant potentiation suggested that myosin phosphorylation may provide a mechanism to enhance contractile force under conditions of submaximal activation during fatigue.

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