The Effect of Trunk Position and Pain Location on Lumbar Extensor Muscle Recruitment Strategies
- Description:
- Healthy participants performed isometric contractions in three positions: neutral, 45° trunk flexion, and 90° trunk flexion; under three conditions: no pain (NP), caudal pain (CrP), and cranial pain (CaP). During each contraction, myoelectric activity of the right and left lumbar extensor muscle was recorded with two HDsEMG of 64 electrodes arranged in 8 columns and 8 rows spaced by 10 mm (semidisposable adhesive matrix; model ELSCH064, OTBioelettronica, Torino, Italy). Furthermore, the force signal generated during the isometric contractions was recorded using the load cell. Dependent variables were calculated for each pain condition (No pain, CrP, CaP) and for each position (neutral, 45° trunk flexion, 90° trunk flexion). Specifically, pain intensity, HDsEMG variables and force were analyzed. With regards to the HDsEMG dependent variable, the ‘Muscle activity amplitude’ corresponded to the mean of the root mean square (RMS) across all filtered channels. This amplitude was subsequently normalized using the mean MVIC amplitude calculated over a 1-second epoch in the corresponding position for each task. In addition, as a complementary analysis to further investigate the effect of trunk position on LEM activation strategies, the muscle activity amplitude normalized to the force produced was computed. To determine the spatial distribution of muscle activity of LEM, the medio-lateral (x) and cranio-caudal (y) coordinates of the centroid were calculated. To facilitate in the interpretation of the spatial coordinates, the right array was flipped along the x-axis, so higher x coordinates indicate a more medial location of the centroid on both sides. The centroid represents the average position of the channels that had absolute RMS values greater than 70% of the maximum absolute RMS value across all channels during the contractions. Specifically, channels with values exceeding 70% of the maximum RMS value were selected, and their estimates were averaged to generate a single estimate for each side, encompassing both x- and y-axis coordinates. For the force generation variables, ‘Force production' corresponds to the mean force exerted in Newton while ‘Force steadiness’ is determined by the CoV of force. As a complementary analysis, the variability in individual pain responses under both CrP and CaP conditions was illustrated by comparing them to the baseline score (no pain condition) for metrics such as muscle activity amplitude, centroid coordinates, and CoV, for each participant. Variability in muscle activity amplitude was determined by calculating the difference between each pain condition and the baseline, and then multiplying it by 100 to represent a percentage of change. For the centroid coordinates and force steadiness, only the differences between each pain conditions and baseline are presented.
- Ducas, Julien
- Contributor(s):
- Ducas, Julien
- Source Repository:
- Dataverse de l'Université du Québec à Trois-Rivières
- Publisher(s):
- Borealis
- Access:
- Public
- URL:
- https://doi.org/10.5683/SP3/7BDPDE
- Publication date:
- 2024-06-12
- Subjects:
- Keywords:
- Identifier:
- https://doi.org/10.5683/SP3/7BDPDE
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