Sustained Maximal Isometric Contraction Research Articles

Associations between apathy and fatigue in patients with neurocognitive disorders

AbstractBackgroundApathy and fatigue are two disabling symptoms of neurocognitive disorders causing a reduction of activity in daily functioning, including in motor activity, and contributing to loss of autonomy. Fatigability is characterized by a reduction in the ability to produce a motor work during a physical task and is a central element in the circle of deconditioning because many activities of daily living require the ability to exert effort over an extended period of time. This study aims to explore the fatigability of apathetic and non‐apathetic patients with neurocognitive disorders (ND).Method20 subjects (out of 40 still to include) with mild to major ND (age= 78,0 ± 6,3y, MMSE= 26,0±2,3) were classified as apathetic (n=10, BMI= 25 ± 2,5) vs non‐apathetic (n=10, BMI= 25 ± 4,5) based on the apathy diagnostic criteria[1]. Subjects performed a 6 minutes walk test, a handgrip test with a sustained maximal isometric contraction for 15 seconds, and a sit to stand task until exhaustion surrounded by a maximal voluntary contraction of extensors knee.ResultPreliminary results showed a significant greater decrease of performance in apathetic patients during the handgrip sustained maximal isometric test (p=0,028). On the 6 minutes walk test and the sit to stand task, no significant differences of fatigability index were found between two groups.ConclusionThe greater decrease of performance during the handgrip test suggests a higher fatigability in apathetic ND patients. This is not yet confirmed by the two other tasks, probably due to the small sample size. As data collection for the study will finish in June 2021, I will present at the conference more reliable results. Reference: [1] Robert P, Lanctôt KL, Agüera‐Ortiz L, et al. Is it time to revise the diagnostic criteria for apathy in brain disorders? The 2018 international consensus group. Eur Psychiatry. 2018;54:71‐76.

Effect of blood flow occlusion on neuromuscular fatigue following sustained maximal isometric contraction.

Sustained isometric maximal voluntary contractions (IMVCs) have blood flow occlusive effects on the microvasculature. However, it is unknown if this effect would be magnified with additional blood flow restriction via a cuff and what the influence on fatigue development would be. Twelve healthy male participants performed a 1-min IMVC of the knee extensors with and without additional blood flow occlusion induced by pneumatic cuff in counterbalanced order on separate days. Vastus lateralis muscle deoxygenation was estimated via near-infrared spectroscopy-derived tissue oxygen saturation (SmO2) throughout the fatiguing contraction. Central and peripheral measures of neuromuscular fatigue (NMF) were assessed via surface electromyography (EMG) and force responses to voluntary contractions and peripheral nerve/transcranial magnetic stimulations before, immediately after, and throughout an 8-min recovery period. SmO2, force, and EMG amplitude decreased during the 1-min IMVC, but there were no between-condition differences. Similarly, no significant (p > 0.05) between-condition differences were detected for any dependent variable immediately after the fatiguing contraction. Transcranial magnetic stimulation (TMS)-derived voluntary activation was lower (p < 0.05) in the no-cuff condition during the recovery period. Sustained IMVC results in a similar degree of muscle deoxygenation and NMF as IMVCs with additional occlusion, providing further evidence that a sustained IMVC induces full ischemia. Novelty NMF etiology, muscle oxygenation, and corticospinal factors during an IMVC are similar with or without an occlusion cuff. Contrary to all other measures, TMS-evaluated voluntary activation returned to baseline faster following the occluded condition.

Fatigue Related Changes in Electromyographic Coherence between Homologous Vastus Lateralis Muscles

Background. The aim of this study was to examine changes in the coherence between EMG signals of homologous quadriceps (vastus lateralis, VL) muscles during in the beginning and the end of multiple sustained isometric bilateral contraction at maximal effort. Methods. Twelve young healthy males participated in the study. The increase in coherence between EMG signals of homologous VL muscles in alpha band, beta band and gamma band was observed during the performance of sustained maximal bilateral isometric contraction with simultaneous decreases in bilateral force, CAR. EMG frequency and EMG amplitude.Results. The increase in beta band coherence during sustained maximal isometric contraction was negatively correlated with the decrease in bilateral force, CAR, EMG amplitude and EMG frequency indicating the possible role of beta coherence to improve VL muscle activation efficiency during maximal bilateral isometric contraction and overcome the effects of VL muscle fatigue in young healthy males. Keywords: muscle fatigue, EMG coherence, bilateral contraction, common drive.

Ge and Gender Differences of Fatigue during Sustained Maximal Isometric Contractions in Adults

Numerous studies have shown that males can generate a higher absolute muscle force, but are less fatigue resistant comparing to females. Even thought aging is accompanied by substantial reductions in muscle mass and strength, it is known, that older adults can sustain a relative submaximal force for a longer duration than young adults. However, findings of quadriceps muscle fatigue after maximal isomeric contractions (MVC) are not well understood, because motor fatigue is task specific and depends of sex, age and the muscle group tested. Thus the aim of our study was to assess gender differences of fatigue from sustained maximal-effort isometric contraction of the knee extensors in older adults. Twenty four young (18–29 years) and twenty older (65–75 years) males and females volunteered to participate in experimental trial. Before experimental procedures anthropometric variables of the subjects were measured (TBF-300 body composition scale „Tanita“ (West Drayton, UK). Subsequently, baseline measures were done: the maximal voluntary contraction (MVC) of knee extensor muscles was measured using an isokinetic dynamometer (System 3; Biodex Medical Systems, Shirley, NY, USA), then involuntary torques were superimposed with electrostimulation of 20Hz and 100Hz stimuli (MG 440; Medicor, Budapest, Hungary). After baseline measures sustained maximum-effort fatiguing contraction of 30 s was conducted. The PTT100 stimulus was superimposed also on the 30-s contraction to asses central activation ratio (CAR). After 5 and 10 min recovery of involuntary (20Hz,100Hz) and voluntary force (MVC) was assessed. Results of our study revealed that baseline involuntary torque, MVC and CAR values of young subjects were greater than older adults (p 0.05). P20 variables of older adults did not changed, but P100 torque values decreased significantly in all groups during fatiguing contraction (p > 0.05). Significant age interaction established in all groups, but sex interaction imposed only in young adult’s baseline measurements (p 0.05), and here was no sex impact observed. Main findings of our study are that older females were more fatigue resistant than older males and young adult groups, whereas MVC decreased in all groups, but the greatest decline established in young adult groups. Moreover, central activation ratio of older females was lower than other groups and recovery of CAR was the slowest in older men group. There was an age-induced peripheral fatigue difference, when young had greater peripheral fatigue then older, and young males suffered greatest peripheral fatigue between all of the groups. Keywords: fatigue, quadriceps muscle, old age, gender differences. DOI: http://dx.doi.org/10.15823/sm.2016.31

Mechanomyographic Response For The Biceps Brachii During A Sustained Maximal Isometric Contraction

Mechanomyographic Response For The Biceps Brachii During A Sustained Maximal Isometric Contraction

The effect of paired associative stimulation on fatigue resistance

Paired associative stimulation (PAS) is a non-invasive stimulation method developed to induce bidirectional changes in the excitability of the cortical projections to the target muscles. However, very few studies have shown an association between changes in motor evoked potentials (MEP) after PAS and behavioral changes in healthy subjects. In the present study we hypothesized that the functional relevance of PAS can be seen during fatiguing exercise, since there is always a central contribution to the development of fatigue. Transcranial magnetic stimulation was applied over the motor cortex to measure changes in the MEPs of the soleus muscle before and after PAS. Furthermore, fatigue resistance was tested during 15s sustained maximal isometric contractions before and after PAS. On average, fatigue resistance did not change after PAS, however the change in excitability correlated significantly with the change in fatigue resistance. Discussion: Functionality of PAS intervention was not demonstrated in this study. However, the observed relationship between excitability and fatigue resistance suggests that PAS might have affected central fatigue during short maximal contractions.

On simulating sustained isometric muscle fatigue: a phenomenological model considering different fiber metabolisms

The present study shows a new computational FEM technique to simulate the evolution of the mechanical response of 3D muscle models subjected to fatigue. In an attempt to obtain very realistic models, parameters needed to adjust the mathematical formulation were obtained from in vivo experimental tests. The fatigue contractile properties of three different rat muscles (Tibialis Anterior, Extensor Digitorium Longus and Soleus) subjected to sustained maximal isometric contraction were determined. Experiments were conducted on three groups [Formula: see text] of male Wistar rats [Formula: see text] using a protocol previously developed by the authors for short tetanic contractions. The muscles were subjected to an electrical stimulus to achieve tetanic contraction during 10s. The parameters obtained for each muscle were incorporated into a finite strain formulation for simulating active and passive behavior of muscles with different fiber metabolisms. The results show the potential of the model to predict muscle fatigue under high-frequency stimulation and the 3D distribution of mechanical variables such as stresses and strains.

Dissociation of recovery of muscle activation and force following a sustained maximal isometric contraction

To investigate time‐dependency of nervous system recovery following muscular contractions subjects (n=10) performed two bouts (B1, B2) of sustained maximal isometric handgrip contractions separated by 10‐min recovery. Force and surface EMG were collected continuously throughout contraction bouts but were analyzed at 15 sec intervals (1 sec segments). iEMG and mean power frequency (MPF) were calculated for the brachioradialis (BR), flexor carpi radialis (FCR) flexor carpi ulnaris (FCU), and flexor digitorum profundus (FDP) muscles. Muscle activation (iEMG‐MPF: BR:68–20%; FCR:72–16%; FCU: 65–20%; FDP:48–50%, respectively) and isometric force (88%) decreased following B1(120‐sec contraction). Following recovery, initial force of B2 was significantly less than B1 (23%); however muscle activation (iEMG) was similar to B1 for BR, FCR and FDP. Initial B2 FCU iEMG activity was lower but increased to B1 levels by 15 sec; remaining similar throughout. MPF was similar and decreased similarly over time in both bouts but tended to be higher at initiation of B2. The mechanical response was similar in both bouts despite differences in initial force generation (B1: y = −0.172x+22.7; R2=0.98; B2: y = −0.182x+17.9 R2=0.97). Incomplete recovery of force observed in B2 suggests interference in excitation‐contraction coupling while fatigue within each bout appears specifically related to changes in muscle activation.

2174 NEAR INFRARED SPECTROSCOPY OF PELVIC FLOOR MUSCLES SHOWS THE EFFECT OF PELVIC FLOOR MUSCLE TRAINING IN WOMEN WITH STRESS INCONTINENCE

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Urodynamic Testing1 Apr 20112174 NEAR INFRARED SPECTROSCOPY OF PELVIC FLOOR MUSCLES SHOWS THE EFFECT OF PELVIC FLOOR MUSCLE TRAINING IN WOMEN WITH STRESS INCONTINENCE lynn stothers, Andrea Marques, Babak Shadgan, and Andrew Macnab lynn stotherslynn stothers Vancouver, Canada More articles by this author , Andrea MarquesAndrea Marques Campinas, Brazil More articles by this author , Babak ShadganBabak Shadgan Vancouver, Canada More articles by this author , and Andrew MacnabAndrew Macnab Vancouver, Canada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.2411AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Near-infrared spectroscopy (NIRS) monitors changes in muscle chromophore concentration of oxygenated (O2Hb), deoxygenated (HHb) and total hemoglobin (tHb). In exercise science, NIRS has been used to monitor rates of muscular fatigue and to modify exercise techniques in athletes. The objective of this study was to demonstrate the feasibility of NIRS to monitor pelvic floor muscle oxygen consumption during pelvic floor muscle training (PFMT) in women with stress urinary incontinence (SUI) compared to healthy controls. METHODS 20 adult women consented. Measures included: voiding diary, body mass index, Incontinence Impact Questionnaire, Sports Medicine Lifestyle Classification, multichannel urodynamics, leak point pressure and Brink Score. NIRS light emitting diodes (785, 808 and 830 nm) were integrated into a vaginal probe. Subjects completed daily and in person PFMT by a PhD physiotherapist weekly x 6 weeks. NIRS was recorded during; a) 3 maximal voluntary contractions, b) 1 minute of sustained maximal isometric contraction and c) 10 rapid continuous contractions. Statistical comparison examined chromophore concentrations before and after PFMT and to controls with p<0.05 as significant. RESULTS 82% of SUI women reported improved continence status following PFMT. SUI women responding to PFMT had a pattern of decreasing musclar O2Hb and tHb, with an increase in HHb during each contraction. Chromophore values returned to baseline following muscle relaxation (fig 1). The magnitude of changes of O2Hb, HHb and tHb were significantly higher after completion of the PFMT program compared to their baseline in women with improved continence. Non responding incontinent women had rates of oxygen decline >50% faster during isometric contraction compared to responders which was correlated to leak point pressure. Control women displayed statistically longer time to muscular fatigue. CONCLUSIONS NIRS interrogation of the pelvic floor demonstrated changes in oxygenation patterns following 6 weeks of PFMT. The feasibility of transvaginal NIRS for evaluation of pelvic floor muscle performance was demonstrated which could allow for personalized PFMT programs in women based on individual rates of muscular fatigue. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e871 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information lynn stothers Vancouver, Canada More articles by this author Andrea Marques Campinas, Brazil More articles by this author Babak Shadgan Vancouver, Canada More articles by this author Andrew Macnab Vancouver, Canada More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Contralateral muscle fatigue in human quadriceps muscle: evidence for a centrally mediated fatigue response and cross-over effect

The purpose of this investigation was to examine the effects of voluntary muscular fatigue in one lower limb and determine whether a 'cross-over' of fatigue is evident in the contralateral limb. Twenty-eight subjects (13 males and 15 females) performed a series of voluntary and evoked isometric contractions of both the dominant (exercised) and non-dominant (non-exercised) leg extensor muscles, prior to and after a fatigue protocol consisting of a 100-s sustained maximal isometric contraction (MVC) performed by the dominant limb only. Force values and surface electromyography (EMG) from the vastus lateralis muscle were obtained allowing for the determination of twitch and compound action potential (M-wave) values. Maximal twitch tension and peak-to-peak amplitude were significantly decreased after the fatigue test in the dominant limb, as was maximal voluntary force (approximately 65 N reduction), EMG activity (approximately 0.1 mV decrease) and voluntary activation (approximately 17% decline). However, no significant changes were observed in the non-dominant limb with respect to twitch and M-wave properties nor in MVC force. The voluntary activation of the non-dominant limb decreased significantly by 8.7% after the fatigue test, which was performed only on the dominant limb. The results of the present study suggest that the decrease in force production in the exercised limb was primarily related to peripheral fatigue mechanisms, with central fatigue making a lesser contribution. Centrally mediated mechanisms appear to be the sole contributor to fatigue in the non-exercised limb suggesting an anticipatory fatigue response and a 'cross-over' of central fatigue between the exercised and non-exercised contralateral limb.

Chronic hypobaric hypoxia does not affect electro-mechanical muscle activities during sustained maximal isometric contractions.

The aim of the study was to evaluate the influence of chronic hypobaric hypoxia [43 days at 5050 m above sea level, a.s.l.] on the electrical and mechanical activities of the elbow flexor and knee extensor muscles during sustained maximal isometric contractions. Seven subjects participated in this study. The maximal voluntary contraction (MVC) of the two muscle groups was assessed. The subjects were then asked to perform a sustained MVC for 1 min, during which surface EMG and MMG signals were recorded before (SL) and after 43 days at high altitude (HA). From the time and frequency domain analysis of the surface EMG and MMG, the root mean square (RMS) and the mean frequency (MF) were then calculated. After HA exposure, in both the investigated muscle groups the results showed that: (1) the MVC did not change; (2) the maximum force decay during the sustained MVC was similar; (3) surface EMG and MMG parameters did not show any statistical difference. These data suggest that exposure to HA did not affect the electrical and mechanical properties of the two investigated muscle groups. We conclude that exposure to chronic hypobaric hypoxia seems to have no effect on the central motor drive or on muscle performance during sustained maximal isometric contractions of the active muscles.

The muscular wisdom hypothesis in human muscle fatigue.

The muscular wisdom hypothesis proposed that the slowing of the motor unit discharge rate during sustained maximal isometric contractions serves to minimize fatigue. The purpose of this review is to examine the applicability of the muscular wisdom hypothesis during other forms of contraction, i.e., prolonged submaximal isometric or dynamic contractions.

Changes in upper limb joint torque patterns and EMG signals with fatigue following a stroke

Purpose : Little is known concerning changes in neuromuscular fatigue following a stroke. The purpose of this study was to evaluate the effect of a stroke on fatigue-related changes in upper limb torque patterns and electromyographic signals. Method : The paretic and non-paretic upper limb of 10 adults (51 - 79 years) who had a stroke (time since stroke: 3 - 75 months) were compared. Subjects had to perform a fatigue task consisting of a sustained maximal isometric contraction in elbow flexion until torque decreased to below 50% of initial. The main variables of interest assessed before, during and after fatigue were: (1) the torque in elbow flexion, as well as associated forces/torques at the shoulder and forearm; (2) the level of voluntary activation; (3) the amplitude (RMS); and (4) frequency content (median frequency) of electromyographic signals. Results : Compared to the non-paretic side, the paretic side showed a lower level of voluntary activation and higher relative torque levels at the forearm and shoulder which could both be exaggerated with fatigue, and a lesser fatigue-related decrease in median frequency. Conclusions : Thus, greater fatigue-related changes in features of the central command (ability to maximally activate a muscle and ability to isolate effort to a muscle group) were observed for the paretic compared with the non-paretic side. This could be a confounding factor when assessing changes in peripheral measures of fatigue following a stroke using voluntary contractions.

Neuromuscular fatigue during maximal concurrent hand grip and elbow flexion or extension

The objective was to investigate muscle fatigue measuring changes in force output and force tremor and electromyographic activity (EMG) during two sustained maximal isometric contractions for 60 s: (1) concurrent hand grip and elbow flexion (HG and EF); or (2) hand grip and elbow extension (HG and EE). Each force tremor amplitude was decomposed into four frequency bands (1–3, 4–10, 11–20, and 21–50 Hz). Surface EMGs were recorded from the flexor digitorum superficialis (FDS), extensor digitorum (ED), biceps brachii (BB) and lateral head of triceps brachii (TB). The HG and EF forces for the HG and EF and the HG force for the HG and EE declined rapidly, whereas the EE force remained almost constant near to the initial value for the first 40 s and then declined. The decrease in EMG amplitude was observed not for the FDS muscle but for the ED muscle. The HG tremor amplitude for each frequency band showed similar decreasing rate, whereas the decreases in EF and EE tremor amplitudes for the lower band (below 10 Hz) were slower than those for the higher band (above 11 Hz). The neuromuscular mechanisms underlying muscle fatigue during sustained maximal concurrent contractions of hand grip and elbow flexion or extension are discussed.

Cardiovascular responses to sustained maximal isometric contractions of the finger flexors.

This study investigated cardiovascular responses to 2 min sustained submaximal (20% MVC) and maximal (100% MVC) voluntary isometric contractions of the finger flexors in healthy young women. Cardiovascular variables investigated were: heart rate (fc), mean arterial pressure (Pa), and stroke volume (SV). Doppler echocardiography was used to estimate SV from measures of aortic diameter (AD) and time-velocity integrals. Preliminary studies indicated that AD did not change significantly after 2 min sustained 100% MVC. Therefore, pre-exercise AD values were used to calculate SV before, during and after exercise. During the 2-min 100% MVC period, fc and Pa increased significantly during the first 30 s of contraction. fc then remained constant during the remainder of the 2-min contraction period, while Pa continued to rise. SV did not change significantly during the 100% MVC task but increased significantly during recovery from sustained 100% MVC. The data suggest that the magnitude of cardiovascular responses to isometric exercise is dependent on the specific task performed, and that there is a different pattern of response for fc, Pa, and SV during 20% and 100% MVC tasks. Unlike fc and Pa, SV did not change significantly during isometric exercise, but increased significantly after sustained 100% MVC.

Long‐lasting supernormal conduction velocity after sustained maximal isometric contraction in human muscle

Local muscle fatigue (1 min maximal voluntary contraction) and recovery were studied by means of surface and invasive EMG on elbow flexors to record the changes in muscle fiber conduction velocity (MFCV), median power frequency (MPF), integrated EMG (IEMG), and force. The main finding was a long-lasting "supernormal" MFCV during recovery, for at least 1 hour. After a normalization phase, the MFCV and MPF continued to increase reaching a steady state at supernormal values after 10-12 min. Mean MFCV increase at 20% MVC after 15-min recovery was 0.58 m.s-1 (12%). Postfatigue IEMG values were increased at all contraction levels. In combination with near normal force levels, this resulted in a decrease in "neuromuscular efficiency" (force/IEMG). We suggest that this IEMG increase is mainly a result of the MFCV increase. The MFCV changes in fastest and slowest fibers found with the invasive method indicate a relatively equal effect on type I and II fiber types. A possible explanation of the supernormal MFCV is muscle fiber swelling, in combination with altered membrane properties.