The role of muscle strength & activation patterns in patellofemoral pain.

BACKGROUND: To investigate the extent to which quadriceps muscle activation and strength are responsible for patellofemoral pain. METHODS: A pain on-off switch system synchronized with a force transducer and surface electromyography was utilized on 32 volunteer patellofemoral pain patients during maximal isometric and squat exercises. FINDINGS: There were 26 patients out of the 32 tested who complained of pain during the squat or isometric test, of these 20 subjects presented a significant advantage for the vastus lateralis compared to the vastus medialis obliquis activation and 12 patients had decreased quadriceps strength of the symptomatic compared to the non symptomatic leg. All patients who demonstrated weak vastus medialis obliquis activation during the isometric exercise possessed the same symptoms during the squat. On the other hand, 9 patients who showed diminished vastus medialis obliquis activation during the squat displayed equal activation between the vastus medialis obliquis and the vastus lateralis during the isometric task. With regard to the timing for the onset of muscle activation, there were only 4 patients who had a difference (P=0.03) between the symptomatic (0.042 s) and non-symptomatic legs (0.011 s). INTERPRETATION: Causes for patellofemoral pain vary and are not necessarily a result of quadriceps strength deficit or vastus medialis obliquis activation weakness. Patellofemoral pain patients who possess lower vastus medialis obliquis activation compared to the vastus lateralis do not necessarily have quadriceps weakness while patients presenting with quadriceps strength deficits do not always have an imbalance between vastus medialis obliquis and vastus lateralis activation.

Improvements of Adaptive Filtering by Optimal Projection to filter different artifact types on long duration EEG recordings.

Adaptive Filtering by Optimal Projection (AFOP) is an automatic method for reducing ocular and muscular artifacts on electro-encephalographic (EEG) recordings. This paper presents two additions to this method: an improvement of the stability of ocular artifact filtering and an adaptation of the method for filtering electrode artifacts. With these improvements, it is possible to reduce almost all the current types of artifacts, while preserving brain signals, particularly those characterising epilepsy. This generalised method consists of dividing the signal into several time-frequency windows, and in applying different spatial filters to each. Two steps are required to define one of these spatial filters: the first step consists of defining artifact spatial projection using the Common Spatial Pattern (CSP) method and the second consists of defining EEG spatial projection via regression. For this second step, a progressive orthogonalisation process is proposed to improve stability. This method has been tested on long-duration EEG recordings of epileptic patients. A neurologist quantified the ratio of removed artifacts and the ratio of preserved EEG. Among the 330 artifacted pages used for evaluation, readability was judged better for 78% of pages, equal for 20% of pages, and worse for 2%. Artifact amplitudes were reduced by 80% on average. At the same time, brain sources were preserved in amplitude from 70% to 95% depending on the type of waves (alpha, theta, delta, spikes, etc.). A blind comparison with manual Independent Component Analysis (ICA) was also realised. The results show that this method is competitive and useful for routine clinical practice.

Back pain during pregnancy and living conditions: a comparison between Beninese and Canadian women.

OBJECTIVE: The objective of this exploratory study was to investigate and underline the contrasts between African and Canadian pregnant women, and their living conditions. We also intended to evaluate how they compared on low back pain, a condition that seems common across all pregnant women everywhere in the world. SUBJECTS AND METHOD: Thirty Beninese and 50 Canadian women were surveyed with demographic disability questionnaires O.D.I at approximately 25 weeks of pregnancy. RESULTS: There were large differences between the two groups due to the differences between the life style. Beninese women were more likely to be self-employed or housewives, while Canadian women were more likely to be employed. Beninese women worked for 18hours more per week, and had on average one more child at home. A higher percentage of Beninese women reported back pain, 83% versus 58% for Canadian women, but the disability scores were in the "moderate disability" range for both groups. A higher percentage of Beninese women also reported at least severe disability, 33% versus 14% for Canadian women. CONCLUSION: The results suggest that the higher percentages of Beninese women affected by back pain and by severe back pain is related to the longer hours worked and more strenuous physical work performed.

Characterization of an electric stimulation protocol for muscular exercise.

OBJECTIVE: The aim of this study is to evaluate the effect of rest time (ten minutes) on muscular strength production during a training session under electrical stimulation. PATIENTS AND METHODS: The isometric force output of the quadriceps femoris muscle was recorded during four sessions of stimulation of five minutes (15 maximal contractions: five seconds on and 15 seconds of rest), on 13 healthy adults. These four sessions are spaced out of ten minutes of recovery. The frequency of current is 100 Hz. RESULTS: At the 60th contraction, muscular force reaches 53 ± 7% of MVC. This value is significantly more important comparatively with a training session without rest time inside (27 ± 6% of MVC). CONCLUSION: The efficiency of electrical stimulation to improve muscle strength seems to be dependent on number of contractions per session with a high level of force production (> =60% de MVC). The protocol including intermediate periods of recovery seems more effective in order to produce a high level of force during all the training session.

Influence of electrical stimulation frequency on skeletal muscle force and fatigue.

OBJECTIVE: The aim of this study is to determine the impact of electrical stimulation frequency on muscle force and fatigue and propose application modalities in regards to sports or clinical rehabilitation training. METHODS: The maximal voluntary contraction (MVC) force of the quadriceps femoris muscle was recorded before, during and after electrical stimulation in 26 healthy adults during 20-minute sessions corresponding to 60 of 5-second contractions separated by 15-second rest periods. Three different frequencies were used: 100, 50 and 20 Hz. RESULTS: With a frequency of 100 Hz, we obtained 71% of the MVC force at the beginning of the session (MVCb). The decrease in muscle force at the end of the session is significantly greater for the highest frequencies respectively 27, 33 and 38% of MVCb for 100, 50 and 20 Hz. CONCLUSION: The impact of electrical stimulation to improve muscle force seems to be dependent on frequency, intensity pulse trains and number of contractions per session. Higher intensity and higher frequency induce stronger muscular contractions, but also a stronger decline in force and thus quick-setting muscle fatigue. Classical 20-minute training sessions with many contractions (60 or more) do not seem appropriate for sports training or clinical rehabilitation programs.

Tissue classification for MRI of thigh using a modified FCM method.

Fuzzy C-means (FCM) has been frequently used to image segmentation in order to separate objects. The most used segmentation attribute is grey level of pixels. Nevertheless, this method can not identify complex image objects because grey level can not take into account all visual information. This paper describes a modified FCM method for tissue classification which integrates separation and fusion operation of partition tree with expert knowledge. Our method has been applied to 26 MRI (Magnetic Resonance Imaging) images of thigh for localizing four main anatomical tissues: muscle, adipose tissue, cortical bone, and spongy bone. A testing dataset of 6500 representative points has been created by an expert. Using our method, we obtain a high classification rate (95.73%) in the test dataset, which largely improved the classification results obtained from existing methods.

[MRI study of the tissue volume progression of lower limbs in hemiplegic subjects]. / Etude de l'évolution des volumes des tissus des membres inférieurs chez le sujet hémiplégique par IRM.

OBJECTIVES: The aim of this paper was to present the first results of a study about lower limbs' soft tissues (fat and muscle) evolution using magnetic resonance images. MATERIALS AND METHODS: Magnetic resonance images method (MRI) was chosen instead of X-ray scanner for its non-invasive and non-radiating properties. Three hemiplegics volunteers were followed during the first 6 months of their therapy. Lower limbs' MRI captures were made at the beginning and in the end of this period. Computerized processing of the data allows automatic recognition of the main lower limb's tissues. Volumes were determined from images and classified in 4 categories (i.e. muscle, fat, spongy bone, cortical bone). RESULTS: Data analysing showed a different evolution of soft tissues in healthy lower limb compared to pathological lower limb. DISCUSSION-CONCLUSION: This results should lead us to a better understanding of therapeutic efficiency.