scholarly journals A Preliminary Study of Dynamic Muscle Function in Hereditary Ataxia

1980 ◽  
Vol 7 (4) ◽  
pp. 367-377 ◽  
Author(s):  
C. Richards ◽  
J.P. Bouchard ◽  
R. Bouchard ◽  
H. Barbeau
Keyword(s):  
Muscle Function ◽  
Autosomal Recessive ◽  
Normal Values ◽  
Vastus Lateralis ◽  
Dynamic Strength ◽  
Knee Extension ◽  
Emg Activity ◽  
Isokinetic Contractions ◽  
Preliminary Study ◽  
Antagonistic Muscles

SUMMARY:Dynamic muscle function was evaluated in nine patients with Friedreich's ataxia (FA) and eight with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). The measurement of torque throughout maximum voluntary isokinetic knee movements was used to quantitatively describe muscle weakness in the ataxic patients. Both FA and ARSACS patients were shown to have decreased dynamic strength in comparison to normal values during knee extension and flexion movements at 30% /s. In the FA patients a lower torqueproducing capacity was seen in the older patients.The electromyographic (EMG) activity was recorded in lower extremity muscles during the movements. In the vastus lateralis (VL), deviations from the normal EMG activation pattern were described in both groups of patients. A reduced amplitude in the EMG activity in the medial hamstrings (MH) was seen in the majority of the patients. An index of coactivation was defined by comparing the EMG activity when a muscle lengthened (antagonistic) to the EMG activity when the same muscle shortened (agonistic) during the isokinetic contractions. In comparison to normal values increased coactivation indexes were present in the VL and MH in patients of both groups. The characteristics of dynamic muscle strength and the activation of agonistic and antagonistic muscles described in the present study will provide the basis of evaluation for the effects of therapy in these patients.

Circadian Force and EMG Activity in Hindlimb Muscles of Rhesus Monkeys

2001 ◽  
Vol 86 (3) ◽  
pp. 1430-1444 ◽  
Author(s):  
J. A. Hodgson ◽  
S. Wichayanuparp ◽  
M. R. Recktenwald ◽  
R. R. Roy ◽  
G. McCall ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Activity Levels ◽  
Hindlimb Muscles ◽  
Cage Activity ◽  
Wide Range ◽  
Postural Muscle ◽  
Low Levels ◽  
Antagonistic Muscles

Continuous intramuscular electromyograms (EMGs) were recorded from the soleus (Sol), medial gastrocnemius (MG), tibialis anterior (TA), and vastus lateralis (VL) muscles of Rhesus during normal cage activity throughout 24-h periods and also during treadmill locomotion. Daily levels of MG tendon force and EMG activity were obtained from five monkeys with partial datasets from three other animals. Activity levels correlated with the light-dark cycle with peak activities in most muscles occurring between 08:00 and 10:00. The lowest levels of activity generally occurred between 22:00 and 02:00. Daily EMG integrals ranged from 19 mV/s in one TA muscle to 3339 mV/s in one Sol muscle: average values were 1245 (Sol), 90 (MG), 65 (TA), and 209 (VL) mV/s. The average Sol EMG amplitude per 24-h period was 14 μV, compared with 246 μV for a short burst of locomotion. Mean EMG amplitudes for the Sol, MG, TA, and VL during active periods were 102, 18, 20, and 33 μV, respectively. EMG amplitudes that approximated recruitment of all fibers within a muscle occurred for 5–40 s/day in all muscles. The duration of daily activation was greatest in the Sol [151 ± 45 (SE) min] and shortest in the TA (61 ± 19 min). The results show that even a “postural” muscle such as the Sol was active for only ∼9% of the day, whereas less active muscles were active for ∼4% of the day. MG tendon forces were generally very low, consistent with the MG EMG data but occasionally reached levels close to estimates of the maximum force generating potential of the muscle. The Sol and TA activities were mutually exclusive, except at very low levels, suggesting very little coactivation of these antagonistic muscles. In contrast, the MG activity usually accompanied Sol activity suggesting that the MG was rarely used in the absence of Sol activation. The results clearly demonstrate a wide range of activation levels among muscles of the same animal as well as among different animals during normal cage activity.

Adaptive control for backward quadrupedal walking. II. Hindlimb muscle synergies

1990 ◽  
Vol 64 (3) ◽  
pp. 756-766 ◽  
Author(s):  
J. A. Buford ◽  
J. L. Smith
Keyword(s):  
High Speed ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Knee Joints ◽  
Emg Activity ◽  
Step Cycle ◽  
Cine Film ◽  
Hip Flexion

1. To compare the basic hindlimb synergies for backward (BWD) and forward (FWD) walking, electromyograms (EMG) were recorded from selected flexor and extensor muscles of the hip, knee, and ankle joints from four cats trained to perform both forms of walking at a moderate walking speed (0.6 m/s). For each muscle, EMG measurements included burst duration, burst latencies referenced to the time of paw contact or paw off, and integrated burst amplitudes. To relate patterns of muscle activity to various phases of the step cycle, EMG records were synchronized with kinematic data obtained by digitizing high-speed cine film. 2. Hindlimb EMG data indicate that BWD walking in the cat was characterized by reciprocal flexor and extensor synergies similar to those for FWD walking, with flexors active during swing and extensors active during stance. Although the underlying synergies were similar, temporal parameters (burst latencies and durations) and amplitude levels for specific muscles were different for BWD and FWD walking. 3. For both directions, iliopsoas (IP) and semitendinosus (ST) were active as the hip and knee joints flexed at the onset of swing. For BWD walking, IP activity decreased early, and ST activity continued as the hip extended and the knee flexed. For FWD walking, in contrast, ST activity ceased early, and IP activity continued as the hip flexed and the knee extended. For both directions, tibialis anterior (TA) was active throughout swing as the ankle flexed and then extended. A second ST burst occurred at the end of swing for FWD walking as hip flexion and knee extension slowed for paw contact. 4. For both directions, knee extensor (vastus lateralis, VL) activity began at paw contact. Ankle extensor (lateral gastrocnemius, LG) activity began during midswing for BWD walking but just before paw contact for FWD walking. At the ankle joint, flexion during the E2 phase (yield) of stance was minimal or absent for BWD walking, and ankle extension during BWD stance was accompanied by a ramp increase in LG-EMG activity. At the knee joint, the yield was also small (or absent) for BWD walking, and increased VL-EMG amplitudes were associated with the increased range of knee extension for BWD stance. 5. Although the uniarticular hip extensor (anterior biceps femoris, ABF) was active during stance for both directions, the hip flexed during BWD stance and extended during FWD stance.(ABSTRACT TRUNCATED AT 400 WORDS)

Medial and Lateral Quadriceps Muscle Activity during Weight-Bearing Knee Extension Exercise

1998 ◽  
Vol 7 (4) ◽  
pp. 248-257 ◽  
Author(s):  
Gilbert M. Willett ◽  
Jason B. Paladino ◽  
Kory M. Barr ◽  
Jill N. Korta ◽  
Gregory M. Karst
Keyword(s):  
Vastus Lateralis ◽  
Weight Bearing ◽  
Quadriceps Muscle ◽  
Surface Emg ◽  
Knee Extension ◽  
Emg Activity ◽  
Exercise Condition ◽  
Elastic Resistance ◽  
Activity Performance ◽  
History Of

The purpose of this study was to determine the effect of weight-bearing terminal knee extension (WBKE) on normalized mean electromyographic (EMG) activity of the vastus medialis oblique (VMO) and vastus lateralis (VL) and the VMO/VL ratio. Sixteen subjects with no history of knee dysfunction participated. Surface EMG data were recorded from the VMO and VL of subjects' test legs as they performed the WBKE exercise under four conditions, three involving elastic resistance and one involving no elastic resistance. EMG data were normalized relative to a maximal isometric quadriceps contraction, and overall mean VMO and VL activity and the VMO/VL ratio were determined for all conditions. The three conditions utilizing elastic resistance showed higher mean VMO and VL activity than the no-resistance condition. The VMO/ VL ratio was not significantly altered during any exercise condition as compared to maximal, quadriceps setting exercise. WBKE against elastic resistance was superior to the same exercise without resistance for generating mean VMO and VL activity. Performance of the WBKE, regardless of the position of lower extremity rotation, does not selectively activate the VMO apart from, or to a greater degree than, the VL.

Training can improve muscle strength and endurance in 78- to 84-yr-old men

1992 ◽  
Vol 73 (6) ◽  
pp. 2517-2523 ◽  
Author(s):  
G. Grimby ◽  
A. Aniansson ◽  
M. Hedberg ◽  
G. B. Henning ◽  
U. Grangard ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Knee Extension ◽  
Emg Activity ◽  
Vastus Lateralis Muscle ◽  
Neural Activation ◽  
Cross Sectional ◽  
Before And After ◽  
The Right

Nine men, 78–84 yr of age, participated in a dynamometer training program 2–3 times/wk, totaling 25 sessions, using voluntary maximal isometric, concentric, and eccentric right knee–extension actions (30 and 180 degrees/s). Measurements of muscle strength with a Kin-Com dynamometer and simultaneous electromyograms (EMG) were performed of both sides before and after the training period. Muscle biopsies were taken from the right vastus lateralis muscle. The total quadriceps cross-sectional area was measured with computerized tomography. Training led to an increase in maximal torque for concentric (10% at 30 degrees/s) and eccentric (13–19%) actions in the trained leg. The EMG activity increased at maximal eccentric activities. The total cross-sectional quadriceps area of the trained leg increased by 3%, but no changes were recorded in muscle fiber areas in these subjects, who already had large mean fiber areas (5.15 microns 2 x 10(3)). The fatigue index measured from 50 consecutive concentric contractions at 180 degrees/s decreased and the citrate synthase activity increased in all but one subject. The results demonstrate that increased neural activation accompanies an increase in muscle strength at least during eccentric action in already rather active elderly men and that muscle endurance may also be improved with training.

Vastus Lateralis and Vastus Medialis Obliquus Activity during a Straight-Leg Raise and Knee Extension with Lateral Hip Rotation

2002 ◽  
Vol 11 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Nicole M. Livecchi ◽  
Charles W. Armstrong ◽  
Mitchell L. Cordova ◽  
Mark A. Merrick ◽  
James M. Rankin
Keyword(s):  
Repeated Measures ◽  
Outcome Measure ◽  
Vastus Lateralis ◽  
Knee Extension ◽  
Emg Activity ◽  
Neutral Position ◽  
Vastus Medialis ◽  
Vastus Medialis Obliquus ◽  
Main Outcome Measure ◽  
Straight Leg Raise

Objective:To compare average electromyogram (EMG) activity of the vastus medialis obliquus (VMO) and vastus lateralis (VL) during straight-leg raise (SLR) and knee extension (KE) with the hip in neutral and lateral rotation.Design:1 × 4 factorial repeated-measures.Setting:Laboratory.Participants:13 male college students.Intervention:SLR with hip flexed at 40°, in neutral position, and maximally laterally rotated and KE with hip in neutral and maximally laterally rotated.Main Outcome Measure:Average EMG activity during each of the 4 conditions, normalized against peak muscle activity during that trial.Results:No differences were observed between exercises in VMO activity (F3,36= 0.646,P> .05), VL activity (F3,36= 1.08,P> .05), or VMO:VL ratio (F3,36= 0.598,P> .05).Conclusions:Electrical activity of the VMO or VL and VMO:VL ratio do not change with hip position or exercise.

Skeletal Muscle Function in Young Patients With Cystic Fibrosis

2016 ◽  
Vol 28 (3) ◽  
pp. 364-373 ◽  
Author(s):  
Lothar Stein ◽  
Constanze Pacht ◽  
Sibylle Junge ◽  
Tobias S. Kaeding ◽  
Momme Kück ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cystic Fibrosis ◽  
Muscle Function ◽  
Vastus Lateralis ◽  
Young Patients ◽  
Forced Expiratory Volume ◽  
Knee Extensors ◽  
Emg Activity ◽  
Skeletal Muscle Function ◽  
M Wave

Purpose:Defects in the gene encoding the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) cause CF. Absence of the CFTR may result in skeletal muscle dysfunction. Here, we tested skeletal muscle function in male adolescent patients with CF.Methods:Ten CF and 10 control participants (age: 16.8 ± 0.6 years) performed 7 repetitive sets of maximum voluntary contractions (MVCs) and underwent an isometric fatigue test of the knee extensors. Electromyography (EMG) activity was recorded from the m. vastus lateralis (VL) and m. vastus medialis (VM).Results:In CF, the MVC torque was lower and correlated with the predicted forced expiratory volume in one second (r = .73, p = .012, n = 10). The M-wave in the VL was shorter in CF than in controls (18.6 ± 0.5 vs. 20.3 ± 0.5 ms, p < .028). In the VM, both the M-wave (4.96 ± 0.61 vs. 7.97 ± 0.60 mV, p = .001) and the EMG (0.29 ± 0.04 vs. 0.47 ± 0.04 mV, p = .004) amplitudes were smaller in CF.Conclusion:The differences in the VL and VM EMG signals between the groups indicate that the lower MVC torque in CF did not result from the direct impact of a CFTR defect on the sarcolemmal excitability; the differences more likely resulted from the less developed musculature in the patients with CF.

Lower limb skeletal muscle function after 6 wk of bed rest

1997 ◽  
Vol 82 (1) ◽  
pp. 182-188 ◽  
Author(s):  
H. E. Berg ◽  
L. Larsson ◽  
P. A. Tesch
Keyword(s):  
Skeletal Muscle ◽  
Lower Limb ◽  
Muscle Function ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Bed Rest ◽  
Emg Activity ◽  
Type I ◽  
Skeletal Muscle Function

Berg, H. E., L. Larsson, and P. A. Tesch. Lower limb skeletal muscle function after 6 wk of bed rest. J. Appl. Physiol. 82(1): 182–188, 1997.—Force, electromyographic (EMG) activity, muscle mass, and fiber characteristics were studied in seven healthy men before and after 6 wk of bed rest. Maximum voluntary isometric and concentric knee extensor torque decreased ( P < 0.05) uniformly across angular velocities by 25–30% after bed rest. Maximum quadricep rectified EMG decreased by 19 ± 23%, whereas submaximum (100-Nm isometric action) EMG increased by 44 ± 28%. Knee extensor muscle cross-sectional area (CSA), assessed by using magnetic resonance imaging, decreased by 14 ± 4%. Maximum torque per knee extensor CSA decreased by 13 ± 9%. Vastus lateralis fiber CSA decreased 18 ± 14%. Neither type I, IIA, and IIB fiber percentages nor their relative proportions of myosin heavy chain (MHC) isoforms were altered after bed rest. Because the decline in strength could not be entirely accounted for by decreased muscle CSA, it is suggested that the strength loss is also due to factors resulting in decreased neural input to muscle and/or reduced specific tension of muscle, as evidenced by a decreased torque/EMG ratio. Additionally, it is concluded that muscle unloading in humans does not induce important changes in fiber type or MHC composition or in vivo muscle contractile properties.

scholarly journals Central excitability does not limit postfatigue voluntary activation of quadriceps femoris

2006 ◽  
Vol 100 (6) ◽  
pp. 1757-1764 ◽  
Author(s):  
J. M. Kalmar ◽  
E. Cafarelli
Keyword(s):  
Evoked Potentials ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Motor Evoked Potentials ◽  
Vastus Lateralis ◽  
Central Fatigue ◽  
Knee Extension ◽  
Voluntary Activation ◽  
Fatigue Protocol ◽  
Central Excitability

After fatigue, motor evoked potentials (MEP) elicited by transcranial magnetic stimulation and cervicomedullary evoked potentials elicited by stimulation of the corticospinal tract are depressed. These reductions in corticomotor excitability and corticospinal transmission are accompanied by voluntary activation failure, but this may not reflect a causal relationship. Our purpose was to determine whether a decline in central excitability contributes to central fatigue. We hypothesized that, if central excitability limits voluntary activation, then a caffeine-induced increase in central excitability should offset voluntary activation failure. In this repeated-measures study, eight men each attended two sessions. Baseline measures of knee extension torque, maximal voluntary activation, peripheral transmission, contractile properties, and central excitability were made before administration of caffeine (6 mg/kg) or placebo. The amplitude of vastus lateralis MEPs elicited during minimal muscle activation provided a measure of central excitability. After a 1-h rest, baseline measures were repeated before, during, and after a fatigue protocol that ended when maximal voluntary torque declined by 35% (Tlim). Increased prefatigue MEP amplitude ( P = 0.055) and cortically evoked twitch ( P < 0.05) in the caffeine trial indicate that the drug increased central excitability. In the caffeine trial, increased MEP amplitude was correlated with time to task failure ( r = 0.74, P < 0.05). Caffeine potentiated the MEP early in the fatigue protocol ( P < 0.05) and offset the 40% decline in placebo MEP ( P < 0.05) at Tlim. However, this was not associated with enhanced maximal voluntary activation during fatigue or recovery, demonstrating that voluntary activation is not limited by central excitability.

scholarly journals Electrical Stimulation Frequency and Skeletal Muscle Characteristics: Effects on Force and Fatigue

2017 ◽  
Vol 27 (4) ◽  
Author(s):  
Maria Vromans ◽  
Pouran Faghri
Keyword(s):  
Electrical Stimulation ◽  
Vastus Lateralis ◽  
Voluntary Contraction ◽  
Current Intensity ◽  
Muscle Size ◽  
Emg Activity ◽  
Abductor Pollicis Brevis ◽  
Fiber Composition ◽  
Initial Drop ◽  
Initial Force

This investigation aimed to determine the force and muscle surface electromyography (EMG) responses to different frequencies of electrical stimulation (ES) in two groups of muscles with different size and fiber composition (fast- and slow-twitch fiber proportions) during a fatigue-inducing protocol. Progression towards fatigue was evaluated in the abductor pollicis brevis (APB) and vastus lateralis (VL) when activated by ES at three frequencies (10, 35, and 50Hz). Ten healthy adults (mean age: 23.2 ± 3.0 years) were recruited; participants signed an IRB approved consent form prior to participation. Protocols were developed to 1) identify initial ES current intensity required to generate the 25% maximal voluntary contraction (MVC) at each ES frequency and 2) evaluate changes in force and EMG activity during ES-induced contraction at each frequency while progressing towards fatigue. For both muscles, stimulation at 10Hz required higher current intensity of ES to generate the initial force. There was a significant decline in force in response to ES-induced fatigue for all frequencies and for both muscles (p<0.05). However, the EMG response was not consistent between muscles. During the progression towards fatigue, the APB displayed an initial drop in force followed by an increase in EMG activity and the VL displayed a decrease in EMG activity for all frequencies. Overall, it appeared that there were some significant interactions between muscle size and fiber composition during progression towards fatigue for different ES frequencies. It could be postulated that muscle characteristics (size and fiber composition) should be considered when evaluating progression towards fatigue as EMG and force responses are not consistent between muscles.

scholarly journals Exploratory study of electromyographic behavior of the vastus medialis and vastus lateralis at neuromuscular fatigue onset

2014 ◽  
Vol 20 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Cristiano Rocha da Silva ◽  
Danilo de Oliveira Silva ◽  
Deisi Ferrari ◽  
Rúben de Faria Negrão Filho ◽  
Neri Alves ◽  
...  
Keyword(s):  
Exploratory Study ◽  
Vastus Lateralis ◽  
Knee Extension ◽  
Neuromuscular Fatigue ◽  
Isometric Contractions ◽  
Median Frequency ◽  
Vastus Medialis ◽  
Mean Square ◽  
Electromyographic Signal ◽  
The Moment

This study aimed to determine and analyze the neuromuscular fatigue onset by median frequency (MDF) and the root mean square (RMS) behavior of an electromyographic signal (EMG). Eighteen healthy men with no prior knee problems initially performed three maximum voluntary isometric contractions (MVIC). After two days of MVIC test, participants performed a fatiguing protocol in which they performed submaximal knee-extension contractions at 20% and 70% MVIC held to exhaustion. The MDF and RMS values from the EMG signals were recorded from the vastus medialis (VM) and the vastus lateralis (VL). Analysis of the MDF and RMS behavior enabled identification of neuromuscular fatigue onset for VM and VL muscles in 20% and 70% loads. Alterations between the VM and VL in the neuromuscular fatigue onset, at 20% and 70% MVIC, were not significant. These findings suggest that the methodology proposal was capable of indicating minute differences sensible to alterations in the EMG signals, allowing identification of the moment when the MDF and the RMS showed significant changes in behavior. The methodology used was also a viable one for describing and identifying the neuromuscular fatigue onset by means of the analysis of EMG signals.

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