Biomedical subjects

B Arsenault

Publications and source records attributed to B Arsenault.

3 recordsLinked to original sources

PubMed1995

Comparisons of mechanical and electromyographical muscular utilization ratios.

The physical loading of a muscle during functional activities can be estimated by the muscular utilization ratio. This ratio is defined as the percentage of muscular involvement relative to the maximal capacity. Either mechanical or electromyographical approaches can be used to obtain the muscle utilization ratio. However, the non-linear relationship between electromyographical activity and muscle force, as well as the non-equivalence between agonist muscles, may create differences between the mechanical muscle utilization ratio calculated from joint moments and the electromyographical muscle utilization ratio calculated from electromyographical data. The aim of this study was to compare, during a squat test, the mechanical muscle utilization ratio and the electromyographical muscle utilization ratio estimated by three different methods; direct linear approximation, second order polynomial regression and linear interpolation. The knee extensor moment and electromyographical data of rectus femoris and vastus medialis of 11 subjects were recorded during both knee extension and squat. Both tests were performed with the knee maintained at 90 degrees of flexion. The results showed that: a) the electromyographical muscle utilization ratio, calculated from the average of vastus medialis and rectus femoris, significantly underestimates the mechanical muscle utilization ratio (ANOVA, p < 0.01), b) the differences between the mechanical muscle utilization ratio and the electromyographical muscle utilization ratio are larger for the direct linear approximation method than for the second order polynomial regression (ANOVA, p < 0.01) or the linear interpolation method (ANOVA, p < 0.01), and c) independent of the method utilized, there is no difference between the electromyographical muscle utilization ratio predicted by the vastus medialis as compared with the rectus femoris (ANOVA, p > 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

A static dynamometer measuring multidirectional torques exerted simultaneously at the hip and knee.

The function of a static dynamometer measuring torques exerted simultaneously in the different anatomical planes of the hip (flexion-extension, abduction-adduction and internal-external rotation) and knee (flexion-extension) is described. Muscular torques were calculated in real time using a desktop computer from measurements of orthogonal forces applied at two locations and the lever arm values measured in each subject. The reliability of the force transducers was explored by examining their output, using calibrated weights, on three different days. The results were identical over this period of time, indicating that the transducers are highly reliable. A mechanical simulator of a lower limb was constructed to generate specific or combined torques of known values at the hip and knee. The torques measured by the dynamometer were found to be highly concordant with the known torques applied by the simulator, indicating that the torque measurements were valid. The usefulness of the dynamometer is demonstrated by evaluating the activity of the rectus femoris and biceps femoris muscles during static efforts exerted in various directions at the hip. In addition, the mechanical action of biarticular muscles at the hip was evaluated by quantification of hip torques during efforts exerted at the knee. From these results, it has been concluded that the present biarticular and multidirectional dynamometer is a valid, reliable and precise instrument that may prove to be useful in evaluating the muscular function of the lower limb.

Biophysics↗

PubMed1991

Influence of body weight support on normal human gait: development of a gait retraining strategy.

The recovery of locomotion, following interactive training with graded weight support, in the adult spinal cat has led to the proposal that removal of body weight may be a therapeutic tool in human gait retraining. There would be benefits, however, in knowing normal responses of humans to partial weight bearing before applying this strategy to patients. In this study, 10 nondisabled male subjects walked on a treadmill while 0%, 30%, 50%, and 70% of their body weight was supported by a modified climbing harness. To dissociate the changes attributable to walking speed from those attributable to body weight, each subject walked at the specified body-weight-support (BWS) levels and at full weight bearing (FWB) at the same speed. Simultaneously, electromyographic data from the right leg muscles, footswitch signals, and video recording of joint motion were collected. The FWB and BWS gaits appeared similar, except at the highest level of BWS studied (ie, 70% of BWS). Significant differences among other BWS and FWB trials at comparable speeds included decreases in percentage of stance, percentage of total double-limb support time, and maximum hip and knee flexor swing angle. Other adaptations to BWS were a reduction in the mean burst amplitude of the muscles that are active during stance and an increase in the mean burst amplitude of the tibialis anterior muscle. The possible implications of this new gait retraining strategy for patients with neurological impairment are discussed. [Finch L, Barbeau H, Arsenault B. Influence of body weight support on normal human gait: development of a gait retraining strategy.

Adult↗