Surface EMG characteristics of people with multiple sclerosis during static contractions of the knee extensors

2010 ◽  
Vol 31 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Sasha M. Scott ◽  
Adrienne R. Hughes ◽  
Stuart D. R. Galloway ◽  
Angus M. Hunter
Keyword(s):  
Multiple Sclerosis ◽  
Surface Emg ◽  
Knee Extensors ◽  
Static Contractions

Cerebral blood flow during static exercise in humans

1990 ◽  
Vol 68 (6) ◽  
pp. 2358-2361 ◽  
Author(s):  
H. B. Rogers ◽  
T. Schroeder ◽  
N. H. Secher ◽  
J. H. Mitchell
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Venous Pressure ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Flow Index ◽  
133Xe Clearance ◽  
Leg Exercise ◽  
Static Contractions ◽  
Clearance Technique

Cerebral blood flow (CBF) was determined in humans at rest and during four consecutive unilateral static contractions of the knee extensors. Each contraction was maintained for 3 min 15 s with the subjects in a semisupine position. The contractions corresponded to 8, 16, 24, and 32% of the maximal voluntary contraction (MVC) and utilized alternate legs. CBF (measured by the 133Xe clearance technique) was expressed by a noncompartmental flow index (ISI). Heart rate and mean arterial pressure increased from resting values of 73 (55-80) beats/min and 88 (74-104) mmHg to 106 (86-138) beats/min and 124 (102-146) mmHg, respectively (P less than 0.0005), during the contraction at 32% MVC. Arterial PCO2 and central venous pressure did not change. Corrected to the average resting PCO2, CBF during control was 55 (35-73) ml.100 g-1.min-1 and remained constant during contractions. Cerebral vascular resistance increased from 1.5 (1.0-2.2) to 2.4 (1.4-3.0) mmHg. 100 g.min.ml-1 (P less than 0.025) at 32% of MVC. There was no difference in CBF between the two hemispheres at rest or during exercise. In contrast to dynamic leg exercise, static leg exercise is not associated with an increase in global CBF when measured by the 133Xe clearance technique.

scholarly journals Effects of long-term resistance training and simultaneous electro-stimulation on muscle strength and functional mobility in multiple sclerosis

2010 ◽  
Vol 17 (4) ◽  
pp. 468-477 ◽  
Author(s):  
Tom Broekmans ◽  
Machteld Roelants ◽  
Peter Feys ◽  
Geert Alders ◽  
Domien Gijbels ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Resistance Training ◽  
Muscle Strength ◽  
Controlled Trial ◽  
Knee Extensor ◽  
Functional Mobility ◽  
Knee Extensors ◽  
Strength Analysis ◽  
Control Group

Background: Resistance training studies in multiple sclerosis (MS) often use short intervention periods. Furthermore, training efficiency could be optimized by unilateral training and/or electrical stimulation. Objective: To examine the effect(s) of unilateral long-term (20 weeks) standardized resistance training with and without simultaneous electro-stimulation on leg muscle strength and overall functional mobility. Methods: A randomized controlled trial involving 36 persons with MS. At baseline (PRE) and after 10 (MID) and 20 (POST) weeks of standardized (ACSM) light to moderately intense unilateral leg resistance training (RESO, n = 11) only or resistance training with simultaneous electro-stimulation (RESE, n = 11, 100 Hz, biphasic symmetrical wave, 400 µs), maximal isometric strength of the knee extensors and flexors (45°, 90° knee angle) and dynamic (60–180°/s) knee-extensor strength was measured and compared with a control group (CON, n = 14). Functional mobility was evaluated using the Timed Get Up and Go, Timed 25 Foot Walk, Two-Minute Walk Test, Functional Reach and Rivermead Mobility Index. Results: Maximal isometric knee extensor (90°, MID: +10 ± 3%, POST: +10 ± 4%) in RESO and knee flexor (45°, POST: +7 ± 4%; 90°, POST: +9 ± 5%) in RESE strength increased ( p < 0.05) compared with CON but RESO and RESE did not differ. Also, impaired legs responded positively to resistance training (unilateral leg strength analysis) and functional reaching increased significantly in RESO (+18%) compared with CON. Dynamic muscle strength and the remaining functional mobility tests did not change. Conclusion: Long-term light to moderately intense resistance training improves muscle strength in persons with MS but simultaneous electro-stimulation does not further improve training outcome.

Comparison of lower limb muscle activity during the dynamic balance test between baseball pitchers and healthy young adults

2020 ◽  
pp. 1-7
Author(s):  
Jeongwoo Jeon ◽  
Jiyeon Lee ◽  
Jiheon Hong ◽  
Jaeho Yu ◽  
Jinseop Kim ◽  
...  
Keyword(s):  
Young Adults ◽  
Muscle Activity ◽  
Vastus Lateralis ◽  
Dynamic Balance ◽  
Neuromuscular Control ◽  
Surface Emg ◽  
Knee Extensors ◽  
Balance Test ◽  
Lower Extremity Muscle ◽  
Baseball Pitchers

BACKGROUND: Dynamic balance is an essential factor for efficient pitching by baseball pitchers. OBJECTIVE: To compare distances reached and lower-extremity muscle activity during the star excursion balance test (SEBT) in baseball pitchers and healthy young adults. METHODS: Nineteen baseball pitchers (BPG) and 20 healthy adults (HAG) were recruited. Surface EMG was used to measure the activity of vastus medialis (VM), vastus lateralis (VL), tibialis anterior, and lateral gastrocnemius. RESULTS: The BPG exhibited greater dynamic balance than in the HAG (p< 0.05) in the posteromedial (PM) and posterolateral (PL) directions. For the PM and PL directions, significantly greater muscle activity of VM and VL was found in the BPG than in the HAG (p< 0.05). CONCLUSION: SEBT performance is characterized by high-level VM and VL muscle activities. Neuromuscular control of knee extensors, such as the VM and VL of pitchers, might affect the dynamic balance measured by the SEBT.

Surface EMG crosstalk quantified at the motor unit population level for muscles of the hand, thigh, and calf

2021 ◽  
Author(s):  
Carina Marconi Germer ◽  
Dario Farina ◽  
Leonardo Abdala Elias ◽  
Stefano Nuccio ◽  
François Hug ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Motor Unit ◽  
Population Level ◽  
Motor Units ◽  
Spatial Filtering ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Plantar Flexors ◽  
Emg Power Spectrum

Crosstalk is an important source of error in interpreting surface electromyography (EMG) signals. Here, we aimed at characterizing crosstalk for three groups of synergistic muscles by the identification of individual motor unit action potentials. Moreover, we explored whether spatial filtering (single and double differential) of the EMG signals influences the level of crosstalk. Three experiments were conducted. Participants (total twenty-five) performed isometric contractions at 10% of the maximal voluntary contraction (MVC) with digit muscles and knee extensors, and at 30% MVC with plantar flexors. High-density surface EMG signals were recorded and decomposed into motor unit spike trains. For each muscle, we quantified the crosstalk induced to neighboring muscles and the level of contamination by the nearby muscle activity. We also estimated the influence of crosstalk on the EMG power spectrum and intermuscular correlation. Most motor units (80%) generated significant crosstalk signals to neighboring muscle EMG in monopolar recording mode, but this proportion decreased with spatial filtering (50% and 42% for single and double differential, respectively). Crosstalk induced overestimations of intermuscular correlation and has a small effect on the EMG power spectrum, which indicates that crosstalk is not reduced with high-pass temporal filtering. Conversely, spatial filtering diminished the crosstalk magnitude and the overestimations of intermuscular correlation, confirming to be an effective and simple technique to reduce crosstalk. This paper presents a new method for the identification and quantification of crosstalk at the motor unit level and clarifies the influence of crosstalk on EMG interpretation for muscles with different anatomy.

Muscle activation and blood flow do not explain the muscle length-dependent variation in quadriceps isometric endurance

2005 ◽  
Vol 98 (3) ◽  
pp. 810-816 ◽  
Author(s):  
R. D. Kooistra ◽  
C. J. de Ruiter ◽  
A. de Haan
Keyword(s):  
Blood Flow ◽  
Blood Supply ◽  
Vastus Lateralis ◽  
Muscle Length ◽  
Rectus Femoris ◽  
Surface Emg ◽  
Knee Extensors ◽  
Emg Activity ◽  
Central Activation ◽  
Full Occlusion

We investigated the role of central activation in muscle length-dependent endurance. Central activation ratio (CAR) and rectified surface electromyogram (EMG) were studied during fatigue of isometric contractions of the knee extensors at 30 and 90° knee angles (full extension = 0°). Subjects ( n = 8) were tested on a custom-built ergometer. Maximal voluntary isometric knee extension with supramaximal superimposed burst stimulation (three 100-μs pulses; 300 Hz) was performed to assess CAR and maximal torque capacity (MTC). Surface EMG signals were obtained from vastus lateralis and rectus femoris muscles. At each angle, intermittent (15 s on 6 s off) isometric exercise at 50% MTC with superimposed stimulation was performed to exhaustion. During the fatigue task, a sphygmomanometer cuff around the upper thigh ensured full occlusion (400 mmHg) of the blood supply to the knee extensors. At least 2 days separated fatigue tests. MTC was not different between knee angles (30°: 229.6 ± 39.3 N·m vs. 90°: 215.7 ± 13.2 N·m). Endurance times, however, were significantly longer ( P < 0.05) at 30 vs. 90° (87.8 ± 18.7 vs. 54.9 ± 12.1 s, respectively) despite the CAR not differing between angles at torque failure (30°: 0.95 ± 0.05 vs. 90°: 0.96 ± 0.03) and full occlusion of blood supply to the knee extensors. Furthermore, rectified surface EMG values of the vastus lateralis (normalized to prefatigue maximum) were also similar at torque failure (30°: 56.5 ± 12.5% vs. 90°: 58.3 ± 15.2%), whereas rectus femoris EMG activity was lower at 30° (44.3 ± 12.4%) vs. 90° (69.5 ± 25.3%). We conclude that differences in endurance at different knee angles do not find their origin in differences in central activation and blood flow but may be a consequence of muscle length-related differences in metabolic cost.

Frequency Analysis of Surface EMG on Knee Extensors in Cases with ACL Insufficiency. Per- and Post-operative Comparison.

1994 ◽  
Vol 43 (4) ◽  
pp. 1403-1405
Author(s):  
Jouji Noguchi ◽  
Takanobu Abe ◽  
Nobuhiro Tanaka ◽  
Takashi Soejima ◽  
Akio Inoue ◽  
...  
Keyword(s):  
Frequency Analysis ◽  
Surface Emg ◽  
Knee Extensors
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