Biomedical subjects

M J Vezina

Publications and source records attributed to M J Vezina.

2 recordsLinked to original sources

PubMed2000

Muscle activation in therapeutic exercises to improve trunk stability.

OBJECTIVE: To evaluate the relative activation amplitudes from 3 abdominal and 2 trunk extensor muscle sites in healthy subjects performing the pelvic tilt, abdominal hollowing, and level 1 of the trunk stability test (TST level 1) exercises and to compare the activation amplitudes among muscle sites and exercises. DESIGN: Prospective comparative study. SETTING: Motion Analysis Research Center, Dalhousie University, Canada. PARTICIPANTS: Twenty-four healthy men (mean age, 30 +/- 8.1 yr [SD]) without low back pain. INTERVENTIONS: Subjects performed 3 exercises in a balanced order, repeating each exercise 5 times while surface electromyography (EMG) was recorded from the 5 muscle sites. Exercises were divided into 2 phases: movement and stabilization. The root-mean-square amplitude of the EMG for each phase was calculated and normalized to the maximal voluntary isometric contraction (MVIC) amplitude for each muscle. A 2-factor repeated-measures analysis of variance (ANOVA) tested the muscle by exercise interaction and the main effects for each phase separately. MAIN OUTCOME MEASURES: Normalized activation amplitude was the main dependent variable. Ensemble-average curves were calculated to examine the phasing of activation. RESULTS: ANOVA showed a statistically significant interaction (p < .05) for both phases, indicating the 3 exercises recruited the 5 muscle sites using different patterns of relative activation. The external oblique (EO) muscle site was activated to higher amplitudes than the other 4 sites in all 3 exercises for both phases. The highest activity was recorded from the EO during the pelvic tilt, just more than 25% of MVIC. The only exercise to recruit the erector spinae to significantly higher amplitudes than the multifidus site was the TST level 1. CONCLUSIONS: Study exercises were not interchangeable for the patterns of trunk muscle activation amplitudes. The exercises did not recruit the abdominal muscles to adequate levels for strengthening for this healthy sample; however, all 5 muscle sites were activated, forming the basis of a stabilizing exercise approach.

Abdominal Muscles↗

PubMedDate not supplied

Differentiating temporal electromyographic waveforms between those with chronic low back pain and healthy controls.

OBJECTIVES: Temporal activation patterns from abdominal and lumbar muscles were compared between healthy control subjects and those with chronic low back pain. STUDY DESIGN: A cross-sectional comparative study. BACKGROUND: Synergist and antagonist coactivity has been considered an important neuromuscular control strategy to maintain spinal stability. Differences in onset times and amplitudes have been reported from trunk muscle EMG recordings between healthy subjects and those with low back pain;however, evaluating temporal EMG waveforms should demonstrate whether differences exist in the ability of those with and those without low back pain to respond to changing perturbations. METHODS: The Karhunen-Loève expansion was applied to the ensemble-average EMG profiles recorded from four abdominal and three trunk extensor muscle sites while subjects performed a leg-lifting task aimed at challenging lumbar spine stability. The principal patterns were derived and the weighting coefficients for each pattern were the main dependent variables in a series of two-factor (group and muscle) mixed ANOVA models. RESULTS: Three principal patterns explained 96% of the variance in the temporal EMG profiles. The ANOVAs revealed statistically significant group and muscle main effects (P<0.05) for the principal pattern and significant group by muscle interactions (P<0.05) for patterns two and three. Post hoc analysis showed that patterns were not different among all muscle sites for the healthy controls, but differences were significant for the low back pain group. CONCLUSIONS: The healthy group coactivated all seven sites with the same temporal pattern of activation. The low back pain group used different activation patterns indicative of a lack of synergistic coactivitation among the muscle sites examined. RELEVANCE: These results provide a foundation for developing a diagnostic classifier of neuromuscular impairment associated with low back pain, that could be used to evaluate the effectiveness of therapeutic interventions to improve muscle coactivation.

Abdominal Muscles↗