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Muscle Recruitment (muscle + recruitment)
Selected AbstractsCerebral oxygenation decreases but does not impair performance during self-paced, strenuous exerciseACTA PHYSIOLOGICA, Issue 4 2010F. Billaut Abstract Aim:, The reduction in cerebral oxygenation (Cox) is associated with the cessation of exercise during constant work rate and incremental tests to exhaustion. Yet in exercises of this nature, ecological validity is limited due to work rate being either fully or partly dictated by the protocol, and it is unknown whether cerebral deoxygenation also occurs during self-paced exercise. Here, we investigated the cerebral haemodynamics during a 5-km running time trial in trained runners. Methods:, Rating of perceived exertion (RPE) and surface electromyogram (EMG) of lower limb muscles were recorded every 0.5 km. Changes in Cox (prefrontal lobe) were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxyhaemoglobin (,[O2Hb], ,[HHb]). Changes in total Hb were calculated (,[THb] = ,[O2Hb] + ,[HHb]) and used as an index of change in regional blood volume. Results:, During the trial, RPE increased from 6.6 ± 0.6 to 19.1 ± 0.7 indicating maximal exertion. Cox rose from baseline to 2.5 km (,,[O2Hb], ,,[HHb], ,,[THb]), remained constant between 2.5 and 4.5 km, and fell from 4.5 to 5 km (,,[O2Hb], ,,[HHb], ,,[THb]). Interestingly, the drop in Cox at the end of the trial coincided with a final end spurt in treadmill speed and concomitant increase in skeletal muscle recruitment (as revealed by higher lower limb EMG). Conclusion:, Results confirm the large tolerance for change in Cox during exercise at sea level, yet further indicate that, in conditions of self-selected work rate, cerebral deoxygenation remains within a range that does not hinder strenuous exercise performance. [source] Simultaneous feedforward recruitment of the vasti in untrained postural tasks can be restored by physical therapyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2003Sallie M. Cowan Abstract Background and purpose: Physical therapy rehabilitation strategies are commonly directed at the alteration of muscle recruitment in functional movements. The aim of this study was to investigate whether feedforward strategies of the vasti in people with patellofemoral pain syndrome can be changed by a physical therapy treatment program in a randomised, double blind, placebo controlled trial. Subjects: Forty (25 female, 15 male) subjects aged 40 yrs or less (27.2 ± 7.8 yrs). Methods: Subjects were allocated to either a placebo treatment or a physical therapy intervention program. The postural challenge used as the outcome measure was not included in the training program. Electromyography (EMG) onsets of vastus medialis obliquus (VMO), vastus lateralis (VL), tibialis anterior and soleus were assessed before and after the six week standardised treatment programs. Results: At baseline the EMG onset of VL occurred prior to that of VMO in both subject groups. Following physical therapy intervention there was a significant change in the time of onset of EMG of VMO compared to VL with the onsets occurring simultaneously. This change was associated with a reduction in symptoms. In contrast, following placebo intervention the EMG onset of VL still occurred prior to that of VMO. Conclusion and discussion: The results indicate that the feedforward strategy used by the central nervous system to control the patella can be restored. Importantly, the data suggest that this intervention produced a change that was transferred to a task that was not specifically included in the training program. Furthermore, the change in motor control was associated with clinical improvement in symptoms. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Diet quality and anthropometry between different sailboarding stylesNUTRITION & DIETETICS, Issue 1 2010Ioannis DOUMTSIOS Abstract Aim:, To identify diet quality and basic anthropometric characteristics of sailboarders. Methods:, The study was conducted in 91 sailboarders, who were divided in two groups according to muscle recruitment during sailing; those performing wave or freestyle surfing formed the WF group (n = 46) and those performing slalom or formula the SF group (n = 45), as the first includes more lower-body muscle recruitment. Diet and anthropometry were evaluated during training days and compared between the two study groups. Results:, The WFs demonstrated lower % body fat (21%), circumferences, skinfolds, body mass index (23.9 kg/m2) and fat mass index (5.1 kg/m2) compared with the SFs (body fat 25.2%, body mass index 26.1 kg/m2 and fat mass index 6.6 kg/m2). Dietary intake was similar and both groups presented a negative energy balance, high cholesterol intake and adequacy in the intake of most micronutrients except for vitamin E of the WF group. The windsurfers achieved a low healthy eating index (54.3 and 58.1 for WF and SF respectively), indicative of a diet in need of improvement and reported the post-training consumption of beer and fast food. Conclusion:, Overall findings suggest the need for dietary counselling in windsurfers, as glycogen depletion is crucial in sailboarding, where one athlete consists of the total boat crew thus, glycogen depletion leading to insufficient energy for technical movements while sailing, has direct effect on the result of the race. [source] Prospective blinded comparison of surface versus wire electromyographic analysis of muscle recruitment in shoulder instabilityPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 1 2009Anju Jaggi Abstract Background.,This pilot study assesses level of agreement between surface and fine-wire electromyography (EMG), in order to establish if surface is as reliable as fine wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder.,Method.,Eighteen participants (11 female) with unstable shoulders were recruited after written consent and ethical approval. Anthropometric information and mean skinfold size for triceps, subscapular, biceps and suprailiac sites were obtained. Triple-stud self-adhesive surface electrodes ('Triode'; Thermo Scientific, Physio Med Services, Glossop, Derbyshire, England) were placed over pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS) at standardized locations. Participants performed five identical uniplanar standard movements (flexion, abduction, external rotation, extension and cross-body adduction). After a 20-minute rest period, a dual-needle technique for fine-wire insertion was performed and the standard movements were repeated. An experienced examiner in each technique reported if muscle activation patterns differed from agreed normal during any movement and were blinded to the other test results. Sensitivity, specificity and Kappa values for level of agreement between methods were calculated for each muscle according to the method of Altman (1991).,Results.,Fifteen participants were successfully tested. Sensitivity, specificity and Kappa values between techniques for each muscle were PM (57%, 50%, 0.07), LD (38%, 85%, 0.22), AD (0%, 76%, ,0.19) and IS (85%, 75%, 0.6). Only IS demonstrated high sensitivity and specificity and a moderate level of agreement between the two techniques. There was no correlation between skinfold size and agreement levels.,Conclusion.,The use of surface EMG may help to classify types of shoulder instability and recognize abnormal muscle patterns. It may allow physiotherapists to direct specific rehabilitation strategies, avoiding strengthening of inappropriate muscles. It has a reasonable degree of confidence to evaluate IS but may have poor sensitivity in detecting abnormal patterns in PM, LD and AD. Further work is required to see if investigator interpretation may have been a factor for the poor level of agreement. Copyright © 2008 John Wiley & Sons, Ltd. [source] Vascular and Biology 04BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue S1 2002A.J. Hayes Background: Angiopoietin-1 (Ang-1) functions physiologically to promote angiogenesis by inducing vascular branching and smooth muscle recruitment. However, we have previously reported to this Society that in an experimental breast cancer model, over-expression of Ang-1 led to tumour inhibition and that expression of Ang-1 in clinical breast cancer specimens was infrequent. We now report a morphological analysis of the tumour microvessels in this model in an attempt to ascertain a mechanism for tumour inhibition. Methods: Ang-1 over-expressing and vector-transfected xenograft tumours used in previous tumourigenicity assays were fixed routinely and sectioned. Endothelial cells and smooth muscle cells were immuno-stained with monoclonal antibodies to CD-31 and smooth muscle actin, visualized with confocal fluorescence microscopy and quantitated with image analysis. Tumours were also immuno-stained for markers of proliferation and apoptosis. Results: Ang-1 expressing tumours displayed striking differences in microvascular morphology at the leading edge of the tumour when compared with controls. Although the number of microvessels was not altered, the peripheral vessels in the Ang-1 tumours were much less ectatic than the dilated immature tumour vessels seen in controls. They were surrounded by a closely adherent continuous layer of smooth muscle cells, absent in controls. In these vessels the ratio of smooth muscle cells to endothelial cells was increased threefold (P < 0.01) and luminal diameter decreased twofold (P < 0.05) compared with controls. The rates of tumour cell proliferation and apoptosis were decreased twofold (P < 0.001) compared with controls. Conclusions: Ang-1 over-expression induced stabilization of microvessels at the tumour periphery, which resulted in a decreased rate of tumour growth. [source] On functional motor adaptations: from the quantification of motor strategies to the prevention of musculoskeletal disorders in the neck,shoulder regionACTA PHYSIOLOGICA, Issue 2010P. Madeleine Abstract Background:, Occupations characterized by a static low load and by repetitive actions show a high prevalence of work-related musculoskeletal disorders (WMSD) in the neck,shoulder region. Moreover, muscle fatigue and discomfort are reported to play a relevant initiating role in WMSD. Aims: To investigate relationships between altered sensory information, i.e. localized muscle fatigue, discomfort and pain and their associations to changes in motor control patterns. Materials & Methods:, In total 101 subjects participated. Questionnaires, subjective assessments of perceived exertion and pain intensity as well as surface electromyography (SEMG), mechanomyography (MMG), force and kinematics recordings were performed. Results:, Multi-channel SEMG and MMG revealed that the degree of heterogeneity of the trapezius muscle activation increased with fatigue. Further, the spatial organization of trapezius muscle activity changed in a dynamic manner during sustained contraction with acute experimental pain. A graduation of the motor changes in relation to the pain stage (acute, subchronic and chronic) and work experience were also found. The duration of the work task was shorter in presence of acute and chronic pain. Acute pain resulted in decreased activity of the painful muscle while in subchronic and chronic pain, a more static muscle activation was found. Posture and movement changed in the presence of neck,shoulder pain. Larger and smaller sizes of arm and trunk movement variability were respectively found in acute pain and subchronic/chronic pain. The size and structure of kinematics variability decreased also in the region of discomfort. Motor variability was higher in workers with high experience. Moreover, the pattern of activation of the upper trapezius muscle changed when receiving SEMG/MMG biofeedback during computer work. Discussion:, SEMG and MMG changes underlie functional mechanisms for the maintenance of force during fatiguing contraction and acute pain that may lead to the widespread pain seen in WMSD. A lack of harmonious muscle recruitment/derecruitment may play a role in pain transition. Motor behavior changed in shoulder pain conditions underlining that motor variability may play a role in the WMSD development as corroborated by the changes in kinematics variability seen with discomfort. This prognostic hypothesis was further, supported by the increased motor variability among workers with high experience. Conclusion:, Quantitative assessments of the functional motor adaptations can be a way to benchmark the pain status and help to indentify signs indicating WMSD development. Motor variability is an important characteristic in ergonomic situations. Future studies will investigate the potential benefit of inducing motor variability in occupational settings. [source] | |||||||||||||