Effect of number of stimuli and timing of twitch application on variability in interpolated twitch torque

2001 ◽  
Vol 90 (3) ◽  
pp. 1036-1040 ◽  
Author(s):  
Esther Suter ◽  
Walter Herzog
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Single Pulse ◽  
Time Intervals ◽  
Large Variability ◽  
Stochastic Nature ◽  
Single Twitch ◽  
Train Stimulation ◽  
Time Point

Application of a supramaximal electrical twitch to the voluntarily contracted muscle is used to assess the level of muscle activation. Large variability in the interpolated twitch torque (ITT) has been observed when repeated stimulations are performed. It is hypothesized that this variability in ITT is caused by the stochastic nature of the timing of twitch application relative to pulses of voluntary excitation trains. Two experiments were performed on 12 subjects each to test this hypothesis. For the first experiment, a single twitch was superimposed on a train stimulation at different time intervals relative to the train pulses. For the second experiment, single, double, triple, or quadruple twitches were applied on a voluntarily contracted muscle. The ITT critically depended on the time point of twitch application: a single pulse applied 5 ms before a train pulse consistently evoked higher ITTs than all other stimulation conditions. Furthermore, variability of the ITT decreased as the number of applied twitches increased. The results support the hypothesis that a large part of the variability in the ITT may be caused by the timing of the superimposed twitch relative to the motor unit trains. The variability may be reduced by increasing the number of superimposed twitches.

scholarly journals Debridement, Antibiotics, and Implant Retention Is a Viable Treatment Option for Early Periprosthetic Joint Infection Presenting More Than 4 Weeks After Index Arthroplasty

2019 ◽  
Vol 71 (3) ◽  
pp. 630-636 ◽  
Author(s):  
Claudia A M Löwik ◽  
Javad Parvizi ◽  
Paul C Jutte ◽  
Wierd P Zijlstra ◽  
Bas A S Knobben ◽  
...  
Keyword(s):  
Treatment Failure ◽  
Periprosthetic Joint Infection ◽  
Joint Infection ◽  
Viable Option ◽  
Time Intervals ◽  
Implant Retention ◽  
Time Point ◽  
Viable Treatment

Abstract Background The success of debridement, antibiotics, and implant retention (DAIR) in early periprosthetic joint infection (PJI) largely depends on the presence of a mature biofilm. At what time point DAIR should be disrecommended is unknown. This multicenter study evaluated the outcome of DAIR in relation to the time after index arthroplasty. Methods We retrospectively evaluated PJIs occurring within 90 days after surgery and treated with DAIR. Patients with bacteremia, arthroscopic debridements, and a follow-up <1 year were excluded. Treatment failure was defined as (1) any further surgical procedure related to infection; (2) PJI-related death; or (3) use of long-term suppressive antibiotics. Results We included 769 patients. Treatment failure occurred in 294 patients (38%) and was similar between time intervals from index arthroplasty to DAIR: the failure rate for Week 1–2 was 42% (95/226), the rate for Week 3–4 was 38% (143/378), the rate for Week 5–6 was 29% (29/100), and the rate for Week 7–12 was 42% (27/65). An exchange of modular components was performed to a lesser extent in the early post-surgical course compared with the late course (41% vs 63%, respectively; P < .001). The causative microorganisms, comorbidities, and durations of symptoms were comparable between time intervals. Conclusions DAIR is a viable option in patients with early PJI presenting more than 4 weeks after index surgery, as long as DAIR is performed within at least 1 week after the onset of symptoms and modular components can be exchanged.

Dealing with Precise and Imprecise Temporal Data in Crisp Ontology

2020 ◽  
Vol 15 (2) ◽  
pp. 30-49 ◽  
Author(s):  
Fatma Ghorbel ◽  
Fayçal Hamdi ◽  
Elisabeth Métais
Keyword(s):  
Set Theory ◽  
Temporal Reasoning ◽  
Time Interval ◽  
Temporal Data ◽  
Time Intervals ◽  
Time Points ◽  
Interval Algebra ◽  
Precise Time ◽  
Time Point

This article proposes a crisp-based approach for representing and reasoning about concepts evolving in time and of their properties in terms of qualitative relations (e.g., “before”) in addition to quantitative ones, time intervals and points. It is not only suitable to handle precise time intervals and points, but also imprecise ones. It extends the 4D-fluents approach with crisp components to represent handed data. It also extends the Allen's interval algebra. This extension allows reasoning about imprecise time intervals. Compared to related work, it is based on crisp set theory. These relations preserve many properties of the original algebra. Their definitions are adapted to allow relating a time interval and a time point, and two time points. All relations can be used for temporal reasoning by means of transitivity tables. Finally, it proposes a crisp ontology that based on the extended Allen's algebra instantiates the 4D-fluents-based representation.

scholarly journals The Effects of Resistance Training on Motor Unit Firing Rates and Muscle Activation

2018 ◽  
Vol 50 (5S) ◽  
pp. 567
Author(s):  
Adam J. Sterczala ◽  
Jonathan D. Miller ◽  
Mandy E. Wray ◽  
Hannah L. Dimmick ◽  
Michael A. Trevino ◽  
...  
Keyword(s):  
Resistance Training ◽  
Motor Unit ◽  
Muscle Activation ◽  
Firing Rates ◽  
Motor Unit Firing

Motor unit firing rates during isometric voluntary contractions performed at different muscle lengths

2004 ◽  
Vol 82 (8-9) ◽  
pp. 769-776 ◽  
Author(s):  
Alejandro Del Valle ◽  
Christine K Thomas
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Muscle Length ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Force Frequency ◽  
Triceps Brachii ◽  
Firing Rates ◽  
Motor Unit Firing ◽  
Voluntary Contractions

Firing rates of motor units and surface EMG were measured from the triceps brachii muscles of able-bodied subjects during brief submaximal and maximal isometric voluntary contractions made at 5 elbow joint angles that covered the entire physiological range of muscle lengths. Muscle activation at the longest, midlength, and shortest muscle lengths, measured by twitch occlusion, averaged 98%, 97%, and 93% respectively, with each subject able to achieve complete activation during some contractions. As expected, the strongest contractions were recorded at 90° of elbow flexion. Mean motor unit firing rates and surface EMG increased with contraction intensity at each muscle length. For any given absolute contraction intensity, motor unit firing rates varied when muscle length was changed. However, mean motor unit firing rates were independent of muscle length when contractions were compared with the intensity of the maximal voluntary contraction (MVC) achieved at each joint angle.Key words: muscle activation, length–tension relationships, force–frequency relationships.

Vastus lateralis surface and single motor unit EMG following submaximal shortening and lengthening contractions

2008 ◽  
Vol 33 (6) ◽  
pp. 1086-1095 ◽  
Author(s):  
Teatske M. Altenburg ◽  
Cornelis J. de Ruiter ◽  
Peter W.L. Verdijk ◽  
Willem van Mechelen ◽  
Arnold de Haan
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Discharge Rate ◽  
Vastus Lateralis ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Single Motor Unit ◽  
Discharge Rates ◽  
Active Motor

A single shortening contraction reduces the force capacity of muscle fibers, whereas force capacity is enhanced following lengthening. However, how motor unit recruitment and discharge rate (muscle activation) are adapted to such changes in force capacity during submaximal contractions remains unknown. Additionally, there is limited evidence for force enhancement in larger muscles. We therefore investigated lengthening- and shortening-induced changes in activation of the knee extensors. We hypothesized that when the same submaximal torque had to be generated following shortening, muscle activation had to be increased, whereas a lower activation would suffice to produce the same torque following lengthening. Muscle activation following shortening and lengthening (20° at 10°/s) was determined using rectified surface electromyography (rsEMG) in a 1st session (at 10% and 50% maximal voluntary contraction (MVC)) and additionally with EMG of 42 vastus lateralis motor units recorded in a 2nd session (at 4%–47%MVC). rsEMG and motor unit discharge rates following shortening and lengthening were normalized to isometric reference contractions. As expected, normalized rsEMG (1.15 ± 0.19) and discharge rate (1.11 ± 0.09) were higher following shortening (p < 0.05). Following lengthening, normalized rsEMG (0.91 ± 0.10) was, as expected, lower than 1.0 (p < 0.05), but normalized discharge rate (0.99 ± 0.08) was not (p > 0.05). Thus, muscle activation was increased to compensate for a reduced force capacity following shortening by increasing the discharge rate of the active motor units (rate coding). In contrast, following lengthening, rsEMG decreased while the discharge rates of active motor units remained similar, suggesting that derecruitment of units might have occurred.

Brain stem reticular influences on lumbar axial muscle activity. II. Temporal aspects

1984 ◽  
Vol 246 (3) ◽  
pp. R396-R401 ◽  
Author(s):  
P. A. Femano ◽  
S. Schwartz-Giblin ◽  
D. W. Pfaff
Keyword(s):  
Brain Stem ◽  
Reticular Formation ◽  
Muscle Activation ◽  
Single Pulse ◽  
Temporal Aspects ◽  
Low Probability ◽  
Axial Musculature ◽  
Epaxial Muscle ◽  
Repetitive Stimulus ◽  
Pulse Stimulation

Epaxial muscle electromyographic (EMG) responses to electrical stimulation of the pontomedullary reticular formation were analyzed for temporal patterns in the urethan-anesthetized rat. Recordings were obtained from the transversospinalis, medial longissimus, and lateral longissimus groups of back muscles. In response to a series of repetitive stimulus trains, the latency of muscle activation decreased with successive trains. Typically a 10-fold decrease in latency required eight to nine stimulus trains (5 trains/s, 25 pulses/train) with currents of 25-30 microA. Individual pulses within long stimulus trains evoked muscle spike potentials at low probability but with short latencies (population range 4-7 ms). The results suggest that whereas influences on lumbar axial musculature from brain stem reticular formation were not powerful enough to evoke muscle spikes with single-pulse stimulation at currents applied in this study, they can yield short, relatively fixed EMG onset latencies in response to individual pulses within stimulus trains once a potentiation phenomenon has occurred.

Tissue carbon dioxide concentrations in rats during acute respiratory acidosis

1960 ◽  
Vol 15 (1) ◽  
pp. 49-52 ◽  
Author(s):  
Alan M. Thompson ◽  
E. B. Brown
Keyword(s):  
Carbon Dioxide ◽  
Skeletal Muscle ◽  
Rate Constant ◽  
Respiratory Acidosis ◽  
Post Mortem ◽  
Time Intervals ◽  
Large Variability ◽  
Capacity Curves ◽  
Carbon Dioxide Concentrations ◽  
Single Exponential

Tissue carbon dioxide concentrations were measured in rats following exposure of the intact animals to 10% or 30% Co2 in oxygen for time intervals from 5 minutes to 2.5 hours. The rats were sacrificed by decapitation. The average normal Co2 concentrations in skeletal muscle, heart and brain were 13.2, 18.6 and 15.1 mm/kg of wet tissue, respectively. The tissue Co2 increased at about the same rate, relative to normal concentration, in each of the three tissues, the concentration approximately doubling in the first 35 minutes on 30% Co2. The skeletal muscle Co2 concentration on 30% Co2 followed a single exponential curve in which the rate constant was 0.036 min.-1. Tissue Co2 capacity curves and data on the rate of Co2 loss post mortem are presented. The barium-soluble Co2 fraction of Conway and Fearon was found to increase in skeletal muscle from 9.4 to 14.6 mm/kg wet tissue when rats had been on 30% Co2 for 1 hour. Even in control rats this fraction showed a large variability and may have little physiological significance. Submitted on April 23, 1959

scholarly journals Imperceptible Somatosensory Single Pulse and Pulse Train Stimulation Oppositely Modulate Mu Rhythm Activity and Perceptual Performance

2020 ◽  
Vol 30 (12) ◽  
pp. 6284-6295
Author(s):  
Fivos Iliopoulos ◽  
Birol Taskin ◽  
Arno Villringer ◽  
Till Nierhaus
Keyword(s):  
Single Pulse ◽  
Mu Rhythm ◽  
Neural Basis ◽  
Pulse Trains ◽  
Perceptual Performance ◽  
The Common ◽  
Three Delays ◽  
Rhythm Activity ◽  
Neural Signaling ◽  
Train Stimulation

Abstract Subliminal stimulation alters conscious perception – a potential mechanism is the modulation of cortical background rhythms especially in the alpha range. Here, in the human somatosensory domain, we assessed effects of subthreshold (imperceptible) electrical finger nerve stimulation – either presented as single pulses or as brief (1 s) 7 Hz pulse trains—on mu-alpha rhythm and perceptual performance. In electroencephalography, subthreshold single pulses transiently (~150–350 ms poststimulus) increased mu activity (event-related synchronization), while, interestingly, subthreshold trains led to prolonged (&gt;1 s) mu desynchronization. In psychophysics, detection of near-threshold target stimuli was consistently reduced when presented together with subthreshold trains (at three delays), whereas for targets paired with subthreshold single pulses detection remained unaffected (30 and 180 ms) or was even elevated (60 ms). Though both imperceptible, single pulses and pulse trains exerted opposite effects on neural signaling and perception. We suggest that the common neural basis is preferential activation of cortical inhibitory interneurons. While the inhibitory impact of a subthreshold single pulse (reflected by mu synchronization) is not psychophysically detectable—rather perception may be facilitated—repetition of the same subthreshold pulse shifts the excitation-inhibition balance toward an inhibitory cortical state (reflected by perceptual impediment) accompanied by mu desynchronization. These differential findings provide novel insights on the notion of alpha activity mediating functional inhibition.

The Effect of Load Uncertainty and Foreperiod Regularity on Anticipatory and Compensatory Neuromotor Control in Catching

Motor Control ◽  
2017 ◽  
Vol 21 (1) ◽  
pp. 1-25 ◽  
Author(s):  
William P. Berg ◽  
Michael R. Hughes
Keyword(s):  
Muscle Activation ◽  
Time Intervals ◽  
Load Uncertainty ◽  
Neuromotor Control ◽  
Weight Condition

Muscle activation was measured using EMG in 28 males (n = 28) while participants caught visually identical balls of known and unknown weights (50, 1.32, 2.18, and 2.99 kg) under variable (1–10s) and constant (3s) foreperiods. EMG integrals were computed for three time intervals before the catch (anticipatory), and one after (compensatory). Load uncertainty caused the CNS to use an anticipatory strategy characterized by preparation to catch balls of an unknown weight by utilizing about 92% of the muscle activation used to catch the heaviest possible ball under the known weight condition. The CNS appeared to scale anticipatory muscle activation to afford an opportunity to catch a ball of an unknown weight between .50 and 2.99 kg. The constant 3s foreperiod, which permitted temporal anticipation, did not influence the anticipatory neuromotor strategy adopted by the CNS to cope with load uncertainty. Load uncertainty also altered compensatory neuromotor control in catching.

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