Sherif M. Waly

Stretching in the rehabilitation of low-back pain patients

The major objective of this investigation was to study the effectiveness of the physical conditioning program used at the University of Miami Comprehensive Pain and Rehabilitation Center in restoring certain elements of the functional abilities of individuals suffering from chronic low-back pain and to evaluate the effectiveness of using a systematically applied, aggressive stretching maneuver as an add-on therapy in the treatment of chronic low-back pain patients. The effect(s) of the proposed stretching maneuver was evaluated. Twenty-eight chronic low-back pain patients were randomly assigned to one of two groups. The control group underwent a multimodal rehabilitation program, and the experimental group underwent the same rehabilitation program in addition to the systematic stretching maneuver under investigation. The results obtained showed that patients undergoing the multimodal rehabilitation program with and without the proposed systematic stretching maneuver showed a significant improvement in their functional abilities as seen from the significant increase in the static strength of the back extensors, with corresponding significant increase in back muscle myoelectric signals. Also, a significant decrease in their pain level was reported after 2 weeks of continuous treatment. The use of the systematic stretching maneuver enhanced the functional gains of chronic low-back pain patients compared to the control group.

Spinal compression tolerance limits for the design of manual material handling operations in the workplace

Spinal compression tolerance limits (SCTL) have been widely used by ergonomists in setting work tolerance limits for manual materials handling (MMH) operations. Thus, the effect of personal and experimental factors on spinal compression tolerance limits (SCTL) is reviewed with the aid of regression and correlation analyses performed on data compiled from the published literature. Tables of SCTL from various sources utilizing large number of specimens and personal factors are presented so that they can be accessed by ergonomists easily. Integrated biomechanical guidelines based on SCTL are provided for the design of MMH operations in the workplace. It is suggested that, in order to reduce the probability of MMH injuries, biomechanical tolerance limits should be set at the damage load instead of the load at fracture. The damage load is the weight which causes the first gross signs of damage such as tissue fluid and blood. An algorithm is described to demonstrate the use of a biomechanics approach to the design of MMH operations.

Biofeedback in back muscle strengthening.

This study was undertaken to investigate the use of electromyography (EMG) biofeedback as an add-on therapy to standard exercise in the restoration of the functional abilities of the trunk extensor muscles in patients suffering from chronic low-back pain (CLBP). A controlled experimental investigation was conducted to study the effectiveness of using the proposed treatment modality in the management of the low-back pain problem. The results obtained indicate that the proposed methodology was an effective tool to achieve a significant improvement in the strength of lumbar paraspinal muscles of chronic low-back pain patients.

A comparative study of two shovel designs

In the present study a modified shovel design with two perpendicular shafts is presented. This modified, two-shaft shovel was compared with a regular shovel. The modified shovel was evaluated and tested in a controlled laboratory environment using surface electromyography recorded from the lumbar paraspinal muscles. The new shovel design was also tested in a field study using ratings of perceived exertion. The results indicate that there was a significant reduction in EMG values of the lumbar paraspinal muscles and a consistent reduction in perceived exertion ratings while the modified shovel was being used for removing dirt in digging trenches up to 90 cm in depth.

Determination of lifting abilities: a comparative study of four techniques.

The main objective of this study was to test the differences among four techniques for the determination of lifting abilities. This study introduced a new submaximal isometric strength testing technique. The proposed test was based on the concept of acceptable maximum effort (AME) which is the level of static exertion the individual is willing to perform voluntarily and comfortably without over-exertion (as opposed to the maximum ability of performance). Twelve male and five female subjects underwent the protocol of the four strength testing techniques investigated: isometric maximum voluntary contraction (MVC); maximum acceptable weight (MAW); maximum dynamic lifting (MDL); and acceptable maximum effort (AME). The results showed that MAW recorded the lowest values followed by AME, then MDL, then MVC. The correlation between AME and MAW was higher than that found between MVC and MAW. Also, it was found that AME is a reproducible measure of muscular functional abilities. On the average, the coefficient of variation was less than 15% for data for both males and females. The implications of these results in determining lifting abilities are discussed.

Psychophysical models for manual lifting tasks

This paper provides two models for males and females to assess the psychophysical maximum acceptable weight of lift. The weight guidelines generated by the models are a function of lifting frequency, height of lift, sagittal or asymmetrical lifting, task duration, container size in the sagittal plane, presence or absence of container couplings, and percentage of the working population. The developed models were generated from a knowledge base available in the published literature. A computer program was written in BASIC to assist the user in determining the safe load that could be handled by a specified working population. Model validation showed that the models developed predict the maximum acceptable weight of lift with a reasonable degree of accuracy. A comparison between the National Institute for Occupational Safety and Health recommendations and those made on the basis of the models developed in this paper is also presented.

Effects of time windowing on the estimated EMG parameters

Electromyography (EMG) provides an in vivo quantitative measure of the musculoskeletal system. The main objective of this study was to investigate the effects of epoch duration on the estimated EMG parameters in both time and frequency domains. The results obtained showed that the window size has no significant effect on the EMG estimated parameters in the time domain. On the other hand, window size has a significant effect on the estimated characteristic frequencies of the power spectrum. The load was found to have significant effects on all EMG parameters used in this study.

Noise reduction using nonlinear optimization modeling

The primary objective of this study is to develop a 3D model to determine the maximum allowable noise exposure time. This model allows the presence of multiple uncorrelated sources. The model provides an optimal arrangement for locating various machinery and equipment in the plant layout and also takes into consideration the acoustic characteristics of materials used in constructing the room. A detailed description of the models and results obtained will be presented and discussed.

Effects of window size and load on estimated myoelectric signal power spectrum

The main objective of this study was to investigate the effects of window size on estimated surface myoelectric signal (MES) parameters in frequency domain. Seven healthy male subjects participated in this study. All subjects were required to perform a sustained isometric muscle contraction corresponding to 25, 50 and 100% of the Maximum Voluntary Contraction (MVC). MES was recorded by surface electrodes for a period of 6 s. Seven different window sizes (64, 128, 256, 512, 1024, 2048, and 4096 ms) were used to estimate the power spectrum. The results obtained showed that the window size has a significant effect on the estimated characteristic frequencies of the power spectrum. The minimum window size that can be used to estimate the power spectrum was found to be 0.5 seconds. The loading level was found to have a significant effect on the frequency domain characteristics. It was observed that the frequencies below the 75th fractile tend to shift upward as the load increases. The upward shift in higher frequencies (≥ 75th fractile) was reversed as the load reached MVC, which indicates that during a constant isometric contraction the shape of the spectrum changes as the force level is increased. The results obtained in this study show that the use of a single spectral variable such as the median frequency may not be sufficient for capturing all the spectral modifications of the MES.

Ergonomic design using computer animation

Computer animation was used to evaluate and improve the ergonomics of an existing cut-up saw workstation in a poultry-processing plant. Based on ergonomics audits of different poultry processing facilities, the manual cut-up saw was identified as one of the workstations having a high incidence of cumulative trauma disorders. A high-end commercial animation software package was used to develop a tool that could be used to measure body joint angles during the performance of the workstation task. Three-dimensional CAD models of the workstation and workers were developed and imported into the animation software. After the data for the existing design was collected, and the computer model was verified, modifications were made in the workstation design using computer animation. The joint angles for the shoulders, elbows, and wrists were significantly improved by lowering the saw four inches, rotating the guide bar 20 degrees, and lowering the bag holder and shackle line. Joint forces and moments were determined to evaluate the proposed design modifications.