Janice M. Moreside

MVC techniques to normalize trunk muscle EMG in healthy women

Normalization of the surface electromyogram (EMG) addresses some of the inherent inter-subject and inter-muscular variability of this signal to enable comparison between muscles and people. The aim of this study was to evaluate the effectiveness of several maximal voluntary isometric contraction (MVC) strategies, and identify maximum electromyographic reference values used for normalizing trunk muscle activity. Eight healthy women performed 11 MVC techniques, including trials in which thorax motion was resisted, trials in which pelvis motion was resisted, shoulder rotation and adduction, and un-resisted MVC maneuvers (maximal abdominal hollowing and maximal abdominal bracing). EMG signals were bilaterally collected from upper and lower rectus abdominis, lateral and medial aspects of external oblique, internal oblique, latissimus dorsi, and erector spinae at T9 and L5. A 0.5s moving average window was used to calculate the maximum EMG amplitude of each muscle for each MVC technique. A great inter-subject variability between participants was observed as to which MVC strategy elicited the greatest muscular activity, especially for the oblique abdominals and latissimus dorsi. Since no single test was superior for obtaining maximum electrical activity, it appears that several upper and lower trunk MVC techniques should be performed for EMG normalization in healthy women.

Trunk Muscle Activation Patterns, Lumbar Compressive Forces, and Spine Stability When Using the Bodyblade

Background and Purpose The objective of this study was to analyze the trunk muscle activation patterns, spine kinematics, and lumbar compressive forces that occur when using the Bodyblade, a popular tool in physical medicine clinics. Subjects The participants were 14 male subjects who were healthy and who were recruited from a university population. Methods With data collected from surface electromyography of selected trunk and shoulder muscles, video analysis, and a 3-dimensional lumbar spine position sensor, modeling methods were used to quantify L4–5 compressive forces and spine stability. Results Large-amplitude oscillation of a vertically oriented Bodyblade resulted in the greatest activation levels of the internal oblique and external oblique muscles (average amplitude=48% and 26% of maximal voluntary isometric contraction, respectively), which were associated with L4–5 compressive forces as high as 4,328 N. Instantaneous stability increased with well-coordinated effort, muscle activation, and compression, but decreased when subjects had poor technique. Discussion and Conclusion The way the Bodyblade is used may either enhance or compromise spine stability. Associated lumbar compressive forces may be inappropriate for some people with compression-intolerant lumbar spine pathology.

Trunk muscle activation patterns and spine kinematics when using an oscillating blade: influence of different postures and blade orientations.

OBJECTIVE To compare trunk muscle activation patterns and trunk kinematics when using an oscillating blade in standing and unsupported sitting postures, and with different orientations of the blade. DESIGN A cross-sectional survey of trunk muscle activities and lumbar motion. SETTING Biomechanics research laboratory. PARTICIPANTS Healthy men (N=13). INTERVENTIONS An oscillating blade was held with 2 hands and oscillated with vertical and horizontal orientations of blade. These exercises were performed both in an erect standing position and in an erect sitting position. MAIN OUTCOME MEASURES Surface electromyography from 14 trunk and 2 shoulder muscles, together with lumbar angular displacement in the 3 planes of motion, were measured while subjects used an oscillating blade at different performance variations. Electromyographic signals were normalized to isometric maximal voluntary contraction (MVC) amplitudes. RESULTS With the exception of internal oblique and anterior deltoid for the horizontal condition, and erector spinae at L5 level for the vertical condition, the subjects posture had no effect on trunk muscular recruitment when using the oscillating blade. The vertical blade orientation resulted in higher amplitudes of spine rotation on the horizontal plane and produced the greatest activation levels of the internal oblique (47% MVC), pectoralis major (33% MVC), and external oblique (23% MVC). On the other hand, the horizontal orientation resulted in the greatest activation levels of erector spinae at T9 level (28% MVC), latissimus dorsi (26% MVC), and rectus abdominis (17% MVC). CONCLUSIONS Muscle activation and spine motion from using an oscillating blade were not affected by the standing or sitting posture of the subject. The choice of blade orientation was more important, because it defined the main group of muscles recruited during the exercise.

Abdominal muscle activation changes if the purpose is to control pelvis motion or thorax motion

The aim of this study was to compare trunk muscular recruitment and lumbar spine kinematics when motion was constrained to either the thorax or the pelvis. Nine healthy women performed four upright standing planar movements (rotations, anterior-posterior translations, medial-lateral translations, and horizontal circles) while constraining pelvis motion and moving the thorax or moving the pelvis while minimizing thorax motion, and four isometric trunk exercises (conventional curl-up, reverse curl-up, cross curl-up, and reverse cross curl-up). Surface EMG (upper and lower rectus abdominis, lateral and medial aspects of external oblique, internal oblique, and latissimus dorsi) and 3D lumbar displacements were recorded. Pelvis movements produced higher EMG amplitudes of the oblique abdominals than thorax motions in most trials, and larger lumbar displacements in the medial-lateral translations and horizontal circles. Conversely, thorax movements produced larger rotational lumbar displacement than pelvis motions during rotations and higher EMG amplitudes for latissimus dorsi during rotations and anterior-posterior translations and for lower rectus abdominis during the crossed curl-ups. Thus, different neuromuscular compartments appear when the objective changes from pelvis to thorax motion. This would suggest that both movement patterns should be considered when planning spine stabilization programs, to optimize exercises for the movement and muscle activations desired.

Hip joint range of motion improvements using three different interventions.

Abstract Moreside, JM and McGill, SM. Hip joint range of motion improvements using three different interventions. J Strength Cond Res 26(5): 1265–1273, 2012—The purpose of this study was to analyze the effect of 3 different exercise interventions plus a control group on passive hip range of motion (ROM). Previous research studies into the methods of improving passive hip mobility have focused on stretching protocols aimed specifically at the hip joint. The effect of core stabilization, motor training, and myofascial stretching techniques on hip mobility in a selected asymptomatic group with limited hip mobility is unclear. In this study, 24 young men with limited hip mobility (<50th percentile) were randomly assigned to 4 groups: stretching, stretching with motor control exercises for the hip and trunk, core endurance with motor control exercises, and the control group. Six-week home exercise programs were individually prescribed based on the assigned group, hip ROM, movement patterns, and timed core endurance. Two-way analyses of variances were conducted to analyze the effect of group assignment on hip ROM improvements. Both stretching groups demonstrated significant improvements in hip ROM (p < 0.05), attaining hip mobility levels at or above the 75th percentile, with rotation improving as much as 56%. The group receiving core endurance and motor control exercises with no stretching also demonstrated a moderate increase in ROM but only significantly so in rotation. Average core endurance holding times improved 38–53%. These results indicate that stretches aimed at the myofascial components of the upper body, in addition to the hip joint, resulted in dramatic increases in hip ROM in a group of young men with limited hip mobility. Hip ROM also improved in the group that did no active stretching, highlighting the potential role of including stabilization or “proximal stiffening training” when rehabilitating the extremities.

Knee joint motion and muscle activation patterns are altered during gait in individuals with moderate hip osteoarthritis compared to asymptomatic cohort

BACKGROUND Knee replacements are common after hip replacement for end stage osteoarthritis. Whether abnormal knee mechanics exist in moderate hip osteoarthritis remains undetermined and has implications for understanding early osteoarthritis joint mechanics. The purpose of this study was to determine whether three-dimensional (3D) knee motion and muscle activation patterns in individuals with moderate hip osteoarthritis differ from an asymptomatic cohort and whether these features differ between contra- and ipsilateral knees. METHODS 3D motions and medial and lateral quadriceps and hamstring surface electromyography were recorded on 20 asymptomatic individuals and 20 individuals with moderate hip osteoarthritis during treadmill walking, using standardized collection and processing procedures. Principal component analysis was used to derive electromyographic amplitude and temporal waveform features. 3D stance-phase range of motion was calculated. A 2-factor repeated analysis of variance determined significant within-group leg and muscle differences. Students t-tests identified between group differences, with Bonferroni corrections where applicable (α=0.05). FINDINGS Lower sagittal plane motion between early and mid/late stance (5°, P=0.004, effect size: 0.96) and greater mid-stance quadriceps activity was found in the osteoarthritis group (P=0.01). Compared to the ipsilateral knee, a borderline significant increase in mid-stance hamstring activity was found in the contra-lateral knee of the hip osteoarthritis group (P=0.018). INTERPRETATION Bilateral knee mechanics were altered, suggesting potentially increased loads and knee muscle fatigue. There was no indication that one knee is more susceptible to osteoarthritis than the other, thus clinicians should include bilateral knee analysis when treating patients with hip osteoarthritis.

Temporal Patterns of the Trunk Muscles Remain Altered in a Low Back–Injured Population Despite Subjective Reports of Recovery

OBJECTIVE To compare temporal activation patterns from 24 abdominal and lumbar muscles between healthy subjects and those who reported recovery from recent low back injury (LBI). DESIGN Cross-sectional comparative study. SETTING University neuromuscular function laboratory. PARTICIPANTS Healthy adult volunteers (N=81; 30 LBI, 51 asymptomatic subjects). INTERVENTIONS Trunk muscle electromyographic activity was collected during 2 difficulty levels of a supine trunk stability test aimed at challenging lumbopelvic control. MAIN OUTCOME MEASURES Principal component (PC) analysis was applied to determine differences in temporal and/or amplitude electromyographic patterns between groups. Mixed-model analyses of variance were performed on PC scores that explained more than 89% of the variance (α=.05). RESULTS Four PCs explained 89% and 96% of the variance for the abdominal and back muscles, respectively, with both muscle groups having similar shapes in the first 3 PCs. Significant interactions or group main effects were found for all PC scores except PC4 for the back extensors. Overall activation amplitudes for both the abdominal and back muscles (PC1 scores) were significantly (P<.05) higher for the LBI group, with both abdominal and back muscles of the LBI group demonstrating an increased response to the leg-loading phase (PC2 scores) compared with the asymptomatic group. Differences were also found between groups in their preparatory activity (PC3 scores), with the LBI group having a higher early relative amplitude of abdominal and back extensor activity. CONCLUSIONS Despite perceived readiness to return to work and low pain scores, muscle activation patterns remained altered in this LBI group, including reduced synergistic coactivation and increased overall amplitudes as well as greater relative amplitude differences during specific phases of the movement. Electromyographic measures provide objective information to help guide therapy and may assist with determining the level of healing and return-to-work readiness after an LBI.

Hip joint motion and gluteal muscle activation differences between healthy controls and those with varying degrees of hip osteoarthritis during walking

PURPOSE Compare gluteal muscle activation patterns and three-dimensional hip joint movements among those with severe hip osteoarthritis (OA), moderate OA and a healthy group during walking. SCOPE 20 individuals with severe OA, 20 with moderate OA and 20 healthy individuals were recruited. Three-dimensional hip motion and surface electromyograms from gluteus maximus and medius were collected during treadmill walking at a self-selected speed. Angular displacement characteristics were calculated for three-dimensional hip motions. Principal component analysis extracted amplitude and temporal features from electromyographic waveforms. Analysis of Variance models and student t-tests using Bonferroni corrections determined between group differences in these gait features (α = 0.05). CONCLUSIONS Sagittal plane hip range of motion was significantly reduced with increasing severity of OA (p < 0.05) where as frontal and transverse plane range of motion was reduced in the severe OA group only (p < 0.05). Activation patterns of gluteus medius and maximus did not differ between the healthy group and those with moderate hip OA (p > 0.05). Individuals with severe OA walking with more prolonged gluteus maximus activation and prolonged and less dynamic gluteus medius activation compared to the other two groups (p < 0.05). This study highlights the changing function of the hip joint during walking with increasing hip OA severity.

Reliability and Repetition Effect of the Center of Pressure and Kinematics Parameters That Characterize Trunk Postural Control During Unstable Sitting Test

Although unstable seat methodology has been used to assess trunk postural control, the reliability of the variables that characterize it remains unclear.

Trunk neuromuscular pattern alterations during a controlled functional task in a low back injured group deemed ready to resume regular activities.

BACKGROUND Trunk neuromuscular alterations have been found in those with chronic low back pain, but less well studied are whether responses are altered in those deemed recovered following an injury. Furthermore, coordinated trunk muscle responses are deemed important for normal spinal function, but there are no studies of temporal patterns early after a low back injury. Determining whether altered trunk muscle patterns exist early after injury could improve our understanding of recovery by providing an objective assessment of functional recovery and risk of re-injury. OBJECTIVE To determine if amplitude and temporal characteristics of trunk neuromuscular patterns differ during a dynamic functional task in a group of participants with recent (within 12 weeks) low back injury (LBI), but deemed ready to resume normal activities, when compared to those with no similar history of injury (ASYM). PARTICIPANTS 35 participants in each group (17 females) were matched for age and body mass index (BMI); (ASYM 36 yrs, BMI 26, LBI 39 yrs, BMI 27). METHODS Participants performed a controlled lifting task (2.9 kg) in a standing maximum reach position, which altered frontal and sagittal plane moments of force. Electromyographic activity of 24 trunk muscle sites, as well as thoracic and pelvis position via an electromagnetic sensor was collected. Principal component analyses extracted the temporal and amplitude waveform patterns. Mixed model ANOVAs tested for effects (p< 0.05) in the main patterns. Preliminary data regarding re-injury status after 1 year was included. RESULTS Three principal patterns explained 97% of the variance, with the LBI group demonstrating increased amplitude and a more constant level of activity compared to the ASYM group. The LBI group also demonstrated more thoracic motion in all 3 axes during this highly constrained task. The no re-injury group had lower activation than the re-injury group, but similar temporal patterns. CONCLUSIONS Despite the perception of readiness to return to work and low pain scores, the temporal and amplitude muscle activation patterns were altered in this LBI group indicating that differences exist compared to a non-low back injured group. The differences are not just relative amplitude differences among muscles but include differences in the temporal response to the flexion moment.