Improvement of spatial resolution in surface-EMG: a theoretical andexperimental comparison of different spatial filters

In the present study, different isotropic and anisotropic filters have been compared by means of theoretical field simulations and experiments in volunteers. A tripole model for an excited motor unit (MU) was used as the basis for simulating the spatial extension of the filter response for each of the investigated filters. The spatial extension is an indicative of the spatial resolution. For the experimental validation, the total number of single motor units was not directly investigated, but the signal-to-noise ratio (SNR) has been determined. Therefore, the potential distribution generated on the skin surface during maximum voluntary contraction has been simultaneous spatially filtered with each of the investigated filters. The simulations show that an isotropic spatial filtering procedure reduces the spatial extension of the filter response and improves the spatial resolution of the electromyography (EMG)-recording arrangement in comparison to anisotropic spatial filters up to 30%. In other words, the spatial selectivity of the arrangement is increased. This improvement in the filter performance is more pronounced for MU's located close to the skin surface than for MU's more distantly located. Additionally, this theoretical improvement in selectivity depends on the direction of the excitation spread relative to the filter alignment. However, the investigations also show that isotropic filters offer an advantage, compared to anisotropic filters, only when the investigated MU is located extremely close to the filter input. The results of the simulations can be confirmed by the experimental investigations. An improvement of 11% in the SNR, relative to anisotropic spatial filters, can be established when using an isotropic spatial filter. This experimental improvement in selectivity is less than the theoretical improvement because the experimentally investigated MU's have less portion in the anisotropic range of the filters than the simulated one at best     

Estimation of the relationship between the noninvasively detected activity of single motor units and their characteristic pathological changes by modelling

Postoperative management of the patellofemoral patient requires the clinician to implement a program which reestablishes functional activities of daily living. This paper will discuss the postoperative management of the patellofemoral patient. Effective rehabilitation techniques are needed to progress the patient. Surgical procedures, such as a lateral retinacular release, proximal realignment, and distal realignments, are frequently utilized techniques; however, long-term clinical outcome studies are lacking. The postoperative protocols discussed utilize an evaluation-based treatment approach model. The model defines evaluation techniques, leading the clinician to a specific rehabilitation pathway. The crucial element of postoperative management focuses on a treatment and exercise approach similar to the nonoperative management. Inappropriate or overly aggressive exercises may lead to possible neurologic dysfunction or delayed muscle function. The clinician must recognize that patients may exhibit articular cartilage damage, and, thus, rehabilitation programs must be designed to minimize the potential risks of progressing this lesion.