Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anticipatory postural adjustments (APAs) are postulated to ameliorate the effects of the disturbance to posture caused by voluntary movement. The primary hypothesis tested in our study was that the magnitude of anticipatory trunk muscle activity is altered by abdominal muscle fatigue. A subsidiary aim of the present study was to examine the directional nature of APAs and use this information to elucidate the central or peripheral nature of changes in postural muscle activity associated with abdominal muscle fatigue. The present study was a within subject design, where abdominal muscle fatigue was induced by a static abdominal curl. Surface EMG was used to assess postural muscle activity in the following trunk muscles; rectus abdominis, erector spinae and internal oblique. Following abdominal muscle fatigue, the magnitude of muscle activity during APAs was significantly reduced by 20% in both the rectus abdominis (fatigued muscle) and the erector spinae (not fatigued) indicating a central rather than peripheral fatigue effect on muscle activity. Abdominal muscle fatigue also induced a 30% increase in the baseline muscle activity of the internal oblique. The changes in magnitude of APA muscle activity may reflect a change in system gain or a change in postural control perhaps related to a change in perceived postural stability. An increase in baseline muscle activity in the internal oblique may compensate partially for the reduction in APAs.
Gait Posture 2006 Nov
PMID:Effects of abdominal muscle fatigue on anticipatory postural adjustments associated with arm raising. 1640 23

The purpose of this study was to quantify changes in postural stability with fatigue of the frontal and sagittal movers of the lower extremities. There were four test sessions, with a randomized order assigned according to the muscles tested and the plane of motion. Subjects were 20 healthy men (age: 22.6+/-2.4 years, height: 173.7+/-3.6 cm, weight: 63.3+/-7.9 kg). During each session, one set of muscle groups was fatigued using isokinetic contractions: ankle plantar/dorsi flexors, ankle evertor/invertors, hip flexor/extensors or hip abductor/adductors. The Biodex Stability System was used to assess anterior/posterior and medial/lateral stability before and after muscle fatigue. Repeated measures ANOVAs revealed that fatigue was associated with a significant increase in all stability indices. Fatigue of the hip movers, whether in the frontal or sagittal planes, led to greater increments in stability indices than fatigue of the ankle musculature. Fatigue of the frontal movers resulted in greater increases in the medial/lateral stability index compared to fatigue of the sagittal movers. In conclusion, fatigue of proximal lower extremity muscles affects postural stability and fatigue of the frontal movers is associated with postural instability in the frontal plane.
Gait Posture 2007 Jul
PMID:Changes in postural stability with fatigue of lower extremity frontal and sagittal plane movers. 1704 37

The purpose of this study was to examine the influence of muscular fatigue of tibialis anterior (TA) on the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered at different constant accelerations (a=0.01, 0.07 and 0.05 ms(-2)). Twenty women (height: 168.9+/-3.36 cm) performed WRTs and RWTs on a motor-driven treadmill, before and after a protocol inducing muscular fatigue of the TA. WRT-speed decreased after TA fatigue whereas RWT-speed did not change except during the intermediate deceleration. Integrated EMG (iEMG) of the activity burst of TA around heel contact was examined in the last steps before transition, the transition step and the first steps after transition. iEMG increased before WRT, then decreased after transition to running. In the RWT the opposite was observed: iEMG increased after RWT, then decreased with decreasing walking speed. After inducing fatigue in the TA, there was a decrease in iEMG in the WRT whereas no influence of fatigue was found on iEMG in the RWT. As a result of TA fatigue, WRT occurred at a lower speed, probably to avoid over-exertion of the TA. This indicates that the TA is a likely determinant of WRT as previously reported. The RWT, on the other hand, was not altered following TA fatigue, which would indicate that WRT and RWT are determined by different factors.
Gait Posture 2007 Apr
PMID:Influence of M. tibialis anterior fatigue on the walk-to-run and run-to-walk transition in non-steady state locomotion. 1704 61

Injury patterns in distance running may be related to kinematic adjustments induced by fatigue. The goal was to measure changes in lower extremity mechanics during an exhaustive run in individuals with and without a history of iliotibial band syndrome (ITBS). Sixteen recreational runners ran to voluntary exhaustion on a treadmill at a self-selected pace. Eight runners had a history of ITBS. Twenty-three reflective marker positions were recorded by an eight-camera 120 Hz motion capture system. Joint angles during stance phase were exported to a musculoskeletal model (SIMM) with the iliotibial band (ITB) modeled as a passive structure to estimate strain in the ITB. For ITBS runners, at the end of the run: (1) knee flexion at heel-strike was higher than control (20.6 degrees versus 15.3 degrees, p=0.01); (2) the number of knees with predicted ITB impingment upon the lateral femoral epicondyle increased from 6 to 11. Strain in the ITB was higher in the ITBS runners throughout all of stance. Maximum foot adduction in the ITBS runners was higher versus control at the start of the run (p=0.003). Maximum foot inversion (p=0.03) and maximum knee internal rotation velocity (p=0.02) were higher versus control at the end of the run. In conclusion, ITB mechanics appear to be related to changes in knee flexion at heel-strike and internal rotation of the leg. These observations may suggest kinematic discriminators for clinical assessment.
Gait Posture 2007 Sep
PMID:Lower extremity mechanics of iliotibial band syndrome during an exhaustive run. 1713 4

Neuromuscular dyscontrol during gait following stroke may be further compromised by increased susceptibility to fatigue. Our purpose was to examine how extended effortful activity affected spatio-temporal gait parameters after stroke. The influence of sub-maximal exercise was assessed among 26 stroke survivors who performed the Six-Minute Walk Test with distance recorded every 2 min. Walking distance decreased 5.8 (S.D. 6.9) m in the second 2-min interval and another 2.3 (S.D. 9.9) m in the final 2 min (p=0.0005). Secondly, we evaluated spatio-temporal gait parameters prior to and immediately following a standardized maximal exercise test on a cycle ergometer in 36 stroke survivors. In contrast to the expected reduction in walking speed, maximal exercise led to a 5.5 (S.D. 11.5) cm/s increase in preferred gait speed (p=0.007) and a 4.5 (S.D. 7.7) steps/min increase in cadence (p=0.0004), but did not affect gait symmetry. Subsequent division of participants by preferred pedaling cadence revealed that individuals with lower preferred cadence had the greatest increase in preferred speed, cadence and paretic leg step length (p<0.01). These unexpected results suggest that potential fatigue-induced effects on gait may have been masked by immediate positive influences of movement rate on walking speed. Such activity-specific effects may have clinical applications for stroke patients and other populations with gait deviations.
Gait Posture 2008 Apr
PMID:Effects of extended effortful activity on spatio-temporal parameters of gait in individuals with stroke. 1762 83

To investigate the effects of muscle fatigue on force sense at the ankle joint, 10 young healthy adults were asked to perform an isometric contra-lateral force ankle-matching task in two experimental conditions of: (1) no-fatigue and (2) fatigue of the plantar-flexor muscles. Measures of the overall accuracy and the variability of the force matching performances were determined using the absolute error and the variable error, respectively. Results showed less accurate and less consistent force matching performances in the fatigue than no fatigue condition, as indicated by decreased absolute and variable errors, respectively. The present findings evidence that muscle fatigue degrades force sense at the ankle joint.
Gait Posture 2008 Oct
PMID:Muscle fatigue degrades force sense at the ankle joint. 1843 57

Quantifying muscle force and fatigue is important in designing ergonomic work stations, in planning appropriate work-rest patterns, and in preventing/assessing the progress of disorders. In 14 subjects (seven males, seven females), muscle force and fatigue were estimated by subjective perception (based on Borg scale CR10) and objective indexes extracted from surface electromyogram (EMG). The experimental protocol consisted of an isometric task selective for the upper trapezius muscle at different force levels (10-80% of maximal voluntary contraction--MVC, in steps of 10%MVC) and one fatiguing contraction (constant force level at 50%MVC until exhaustion). Surface EMG signals were detected by a two-dimensional (2D) array of electrodes placed half way between C7 and the acromion. The following variables were calculated from EMG signals: muscle fibre conduction velocity (CV), root mean square value (RMS), mean frequency of the power spectrum (MNF), fractal dimension (FD), and entropy. All detected signals were also used to build topographical maps of RMS. Both subjective and objective indications of force and fatigue can provide information on exerted force and endurance time (ET). In particular, Borg ratings, RMS, and entropy were significantly related to force, and the rate of change of CV, MNF, FD, and Borg ratings were predictive of the endurance time. Moreover, significant differences were found in Borg ratings between males and females. The correlation coefficient of pairs of topographical maps of RMS was high (of the order of 0.8). This reflects a characteristic spatial-temporal recruitment of upper trapezius motor units that is not affected by force levels or fatigue.
Gait Posture 2008 Aug
PMID:Assessment of force and fatigue in isometric contractions of the upper trapezius muscle by surface EMG signal and perceived exertion scale. 1849 Jan 65

This study examines how lower extremity fatigue of the quadriceps alters gait variables related to slip propensity. Sixteen healthy young adults were recruited to walk across vinyl floor surfaces in states of fatigue and no fatigue. Kinematic and kinetic data were collected using a three-dimensional motion analysis system and force plates. The results indicated a significant increase in both the heel contact velocity and required coefficient of friction and a decrease in the transitional acceleration of the whole body center of mass and peak knee joint moment in the fatigue trials. Thus, suggesting that slip propensity could increase with fatigue. Additionally, there was increased knee flexion and reduced ankle dorsiflexion at the heel contact phase of the gait cycle during fatigue trials. These findings provide new insights into the biomechanical relationship between localized muscle fatigue and gait parameters associated with slip propensity. The present study concluded that localized muscle fatigue affects gait parameters and hence can be considered as a potential risk factor for slip-induced falls.
Gait Posture 2008 Nov
PMID:Effects of quadriceps fatigue on the biomechanics of gait and slip propensity. 1851 22

The purpose of this study was to assess plantar pressure deviations due to fatigue. Plantar pressure was assessed using a portable system while eleven healthy subjects performed three walking tests, one before, one immediately after and another 30-min after intensive running. Pressure peak, intra-subject coefficient of variation and relative impulse were recorded. Significant decrease in pressure peak and the relative impulse under the heel and the midfoot along with significant increase in pressure peak and relative impulse under the forefoot were observed 30 min after the run. After a 30-min rest, the heel and forefoot loading remained significantly affected compared to the pre-test conditions while variability, step length and frequency remained unchanged. The study demonstrates short- and long-term plantar pressure deviations due to fatigue induced by an intensive 30-min run, while previous studies showed negligible deviation of the ground reaction force.
Gait Posture 2008 Nov
PMID:The effects of fatigue on plantar pressure distribution in walking. 1858 95

This study tested the effect of lower limb muscle fatigue induced by series of high-level isometric contractions (IC) on postural adjustments and maintenance of erect posture. Subjects (N=7) displaced a bar (grasp-bar) forward with both hands at maximal velocity towards a target ("bilateral forward-reach" task, BFR), before and after a procedure designed to induce fatigue in dorsal leg muscles. This procedure included IC at 60% of maximum. Postural joint and grasp-bar motion, along with electrical activity of postural and focal muscles were recorded. Integrated electromyographical (EMG) activity per 20 ms period ranging from 400 ms before BFR onset (t0) to 400 ms after t0 was compared before and after the fatiguing procedure. This time-window included "anticipatory", "on-line" and "corrective" postural adjustments, i.e. those postural adjustments occurring before (APAs), during (OPAs) and after (CPAs) BFR, respectively. In contrast to the literature, results showed that the fatiguing procedure had no effect on muscle excitation or timing in any of the recorded postural muscles, regardless of APA, OPA or CPA-related time-window. Therefore, the postural drive did not change with fatigue. Furthermore, the peak-to-peak motion at postural joints did not change. Postural maintenance was therefore not additionally challenged. These results are in line with the hypothesis that the effect of fatigue on postural adjustments is dependent on the adequacy between fatigued motor units (MUs) and MUs recruited during the postural adjustments. Increasing IC intensity during the fatiguing procedure might therefore not necessarily exacerbate the effect of fatigue on postural control highlighted during lower level IC.
Gait Posture 2009 Jan
PMID:Effect of lower limb muscle fatigue induced by high-level isometric contractions on postural maintenance and postural adjustments associated with bilateral forward-reach task. 1872 52


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>