Cheryl L. Hubley-Kozey

Neuromuscular and Lower Limb Biomechanical Differences Exist Between Male and Female Elite Adolescent Soccer Players During an Unanticipated Run and Crosscut Maneuver

Background Female athletes are 2 to 8 times more likely than male athletes to injure the anterior cruciate ligament during a noncontact athletic maneuver. Identifying anterior cruciate ligament injury risk factors in female athletes may help with the development of preventive training programs aimed at reducing injury rates. Hypothesis Differences between genders in lower limb kinematics, kinetics, and neuromuscular patterns will be identified in an adolescent soccer population during an unanticipated side-cut maneuver. Study Design Controlled laboratory study. Methods Forty-two elite adolescent soccer players (21 male and 21 female) performed an unanticipated side-cut maneuver, with the 3-dimensional kinematic, kinetic, and electromyographic lower limb data being analyzed using principal component analysis. Results The female athletes had higher gastrocnemius activity, normalized to maximal voluntary isometric contractions, and a mediolateral gastrocnemius activation imbalance that was not present in the male athletes during early stance to midstance of the side-cut. Female athletes demonstrated greater rectus femoris muscle activity throughout stance, and the only hamstring difference identified was a mediolateral activation imbalance in male athletes only. Female athletes performed the side-cut with less hip flexion and more hip external rotation and also generated a smaller hip flexion moment compared with the male athletes. Conclusion This is the first study to identify gender-related differences in gastrocnemius muscle activity during an unanticipated cutting maneuver. Clinical Relevance The increased and imbalanced gastrocnemius muscle activity, combined with increased rectus femoris muscle activity and reduced hip flexion angles and moments in female subjects, may all have important contributing roles in the higher noncontact ACL injury rates observed in female athletes.

The Effect of Total Knee Arthroplasty on Knee Joint Kinematics and Kinetics During Gait

This study determined how total knee arthroplasty (TKA) altered knee motion and loading during gait. Three-dimensional kinematic and kinetic gait patterns of 42 patients with severe knee osteoarthritis were collected 1 week prior and 1-year post-TKA. Principal component analysis extracted major patterns of variability in the gait waveforms. Overall and midstance knee adduction moment magnitude decreased. Overall knee flexion angle magnitude increased due to an increase during swing. Increases in the early stance knee flexion moment and late stance knee extension moment were found, indicating improved impact attenuation and function. A decrease in the early stance knee external rotation moment indicated alteration in the typical rotation mechanism. Most changes moved toward an asymptomatic pattern and would be considered improvements in motion, function, and loading.

Co-activation differences in lower limb muscles between asymptomatic controls and those with varying degrees of knee osteoarthritis during walking

BACKGROUND Increased muscle co-activation during gait has been identified as a neuromuscular alteration associated with knee osteoarthritis, however levels of co-activation among different osteoarthritis severity have not been established. The purpose of this study was to determine if differences in co-activation could be detected among asymptomatic controls, those with moderate and those with severe osteoarthritis using a co-activation index and a pattern recognition technique. METHODS Surface electromyograms from vastus lateralis and medialis, lateral and medial hamstring and gastrocnemius pairs were recorded from 63 asymptomatic, 59 moderate and 48 severe osteoarthritic subjects during self-selected walking. A co-activation index was calculated over the initial stance for four medial and lateral muscle pairs. The four co-activation indices were tested among groups using a one factor ANOVA (alpha=0.05). Gait waveform pattern recognition procedures were applied to yield a principal pattern, scored for each muscle site and subject. A mixed model ANOVA (group-muscle) tested for principal pattern score differences. FINDINGS A significant group effect was found (P<0.05) for all four co-activation indices. Principal pattern one captured the amplitude and general shape of activity throughout the entire stance phase. ANOVA revealed a significant (P<0.05) group by muscle interaction for the principal pattern scores. Significant differences were found among all three groups and between the two osteoarthritic groups for both measures. INTERPRETATION The co-activation indices and principal patterns identified that lateral site differences occurred among all three groups with medial site differences between the two osteoarthritic groups. These findings suggest that measures of muscle co-activity provide additional information related to knee osteoarthritis severity.

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.

Foot progression angle and the knee adduction moment: a cross-sectional investigation in knee osteoarthritis

OBJECTIVE To test the hypothesis that an association exists between the characteristics of the knee adduction moment and foot progression angle (FPA) in asymptomatic individuals and those with mild to moderate and severe knee osteoarthritis (OA). DESIGN Fifty asymptomatic individuals, 46 patients with mild to moderate and 44 patients with severe knee OA were recruited. Maximum knee adduction moment during late stance and principal component analysis (PCA) were used to describe the knee adduction moment captured during gait. Multiple regression models were used for each of the three group assignments to analyze the association between the independent variables and the knee adduction moment. RESULTS FPA explained a significant amount of the variability associated with the shape of the knee adduction moment waveform for the asymptomatic and mild to moderate groups (P<0.05), but not for the severe group (P>0.05). Walking velocity alone explained significant variance associated with the shape of the knee adduction moment in the severe OA group (P<0.05). CONCLUSION A toe out FPA was associated with altered knee adduction moment waveform characteristics, extracted using PCA, in asymptomatic individuals and those with mild to moderate knee OA only. These findings are directly implicated in medial knee compartment loading. This relationship was not evident in those with severe knee OA.

The association between knee joint biomechanics and neuromuscular control and moderate knee osteoarthritis radiographic and pain severity

OBJECTIVE The objective of this study was to determine the association between biomechanical and neuromuscular factors of clinically diagnosed mild to moderate knee osteoarthritis (OA) with radiographic severity and pain severity separately. METHOD Three-dimensional gait analysis and electromyography were performed on a group of 40 participants with clinically diagnosed mild to moderate medial knee OA. Associations between radiographic severity, defined using a visual analog radiographic score, and pain severity, defined with the pain subscale of the WOMAC osteoarthritis index, with knee joint kinematics and kinetics, electromyography patterns of periarticular knee muscles, BMI and gait speed were determined with correlation analyses. Multiple linear regression analyses of radiographic and pain severity were also explored. RESULTS Statistically significant correlations between radiographic severity and the overall magnitude of the knee adduction moment during stance (r²=21.4%, P=0.003) and the magnitude of the knee flexion angle during the gait cycle (r²=11.4%, P=0.03) were found. Significant correlations between pain and gait speed (r²=28.2%, P<0.0001), the activation patterns of the lateral gastrocnemius (r²=16.6%, P=0.009) and the medial hamstring (r²=10.3%, P=0.04) during gait were found. The combination of the magnitude of the knee adduction moment during stance and BMI explained a significant portion of the variability in radiographic severity (R(2)=27.1%, P<0.0001). No multivariate model explained pain severity better than gait speed alone. CONCLUSIONS This study suggests that some knee joint biomechanical variables are associated with structural knee OA severity measured from radiographs in clinically diagnosed mild to moderate levels of disease, but that pain severity is only reflected in gait speed and neuromuscular activation patterns. A combination of the knee adduction moment and BMI better explained structural knee OA severity than any individual factor alone.

Effectiveness of an Exercise Program to Improve Forward Head Posture in Normal Adults: A Randomized, Controlled 10-Week Trial

Abstract Forward head posture (FHP) is most often described as excessive anterior positioning of the head in relation to a vertical reference line, involving increased cervical spine lordosis (head forward, middle cervical spine extended, lower cervical spine flexed) and rounded shoulders with thoracic kyphosis. Although exercise is routinely used to improve FHP, relatively little data exists on efficacy. The present study was designed to examine the impact of a 10-week targeted and progressive home exercise program on improving FHP. As improvement through exercise of postural alignment depends upon participants adhering to the program, we also looked at issues related to exercise compliance. Seventeen control (C) and 23 exercise (E) participants with a FHP deviation were part of this program. Pre- and post-exercise postural measurements of FHP were obtained from the sagittal plane using the Biotonix TM Postural Analysis System; in addition neck flexion range of motion was measured. Participants were randomly assigned to C or E groups. The E group performed neck extensor and pectoralis major stretches and deep neck flexor and shoulder retractor strengthening exercises for the 10-week period. Two-factor (group, pre-test/post-test) analysis of variance models were used to test main effects and interactions. There were no significant differences (p>0.05) between groups on any pre-test measure. For the E group, there were significant differences and interactions (p<0.05) between pre- and post-tests and also between the E and C groups at post-test for range of motion and one postural measurement. The results demonstrate that a short, home-based targeted exercise program can improve postural alignment related to FHP. These results provide a foundation for further development of postural improvement programs that include an exercise component.

Gender differences exist in neuromuscular control patterns during the pre-contact and early stance phase of an unanticipated side-cut and cross-cut maneuver in 15-18 years old adolescent soccer players

Non-contact ACL injuries generally occur as the foot contacts the ground during cutting or landing maneuvers and the non-contact ACL injury rate is 2-8 times greater in females compared to males. To provide insight into the gender bias of this injury, this study set out to identify gender differences in the neuromuscular response of the quadriceps, hamstrings and gastrocnemii muscles in elite adolescent soccer players during the pre-contact and early stance phases of an unanticipated side-cut and cross-cut. For the early stance phase of the two maneuvers, females demonstrated greater rectus femoris activity compared to males. Throughout the pre-contact phase of the maneuvers, a rectus femoris activation difference was identified with females having an earlier and more rapid rise in muscle activity as initial ground contact approached. Females demonstrated greater lateral and medial gastrocnemii activity for the pre-contact and early stance phases of the side-cut and greater lateral gastrocnemii activity during early stance of the cross-cut. Timing of hamstring activity also differed between genders prior to foot contact. The differences suggest that the activation patterns observed in females might not be providing adequate joint protection and stability, thereby possibly having a contributing role towards increased non-contact ACL injuries in females.

Explaining the hip adduction moment variability during gait: Implications for hip abductor strengthening

BACKGROUND There is emerging interest in hip abductor function during gait and its potential relationship to knee joint pathology. During gait, the hip abductor muscles are primarily responsible for generating moments of force to control frontal plane movement. The current study investigated the relationship between hip abductor muscle function and frontal plane hip moments of force during gait. METHODS Frontal plane hip moments of force and electromyographic features of gluteus medius were measured during walking in 22 healthy individuals. Hip abductor strength, subject anthropometrics and gait velocity were recorded. Multiple regression models were used to evaluate the relationship between the anthropometric, velocity, strength and electromyographic variables and the initial and mid-stance magnitude of the hip adduction moment. FINDINGS A positive relationship was found between the initial peak moment (Nm), and both body mass and gait speed (R(2)=90%). Body mass (positive) and hip abductor strength (negative) explained significant levels of mid-stance magnitude variability (R(2)=62.5%). Gait speed (positive) explained significant levels of variability in the normalized initial peak moment (Nm/kg) (R(2)=52%). No variables were included in the normalized mid-stance moment model (P>0.05). INTERPRETATION Body mass was the key factor associated with high hip adduction moments during initial and mid-stance of the gait cycle. Increased gait velocity was associated with higher initial peaks and higher muscle strength was associated with lower mid-stance magnitude of the external hip adductor moment during walking. These findings suggest that in a healthy adult population, hip abductor strength and activation were not directly related to the hip adduction moment magnitude during gait.

The Feasibility of performing resistance exercise with acutely ill hospitalized older adults

BackgroundFor older adults, hospitalization frequently results in deterioration of mobility and function. Nevertheless, there are little data about how older adults exercise in the hospital and definitive studies are not yet available to determine what type of physical activity will prevent hospital related decline. Strengthening exercise may prevent deconditioning and Pilates exercise, which focuses on proper body mechanics and posture, may promote safety.MethodsA hospital-based resistance exercise program, which incorporates principles of resistance training and Pilates exercise, was developed and administered to intervention subjects to determine whether acutely-ill older patients can perform resistance exercise while in the hospital. Exercises were designed to be reproducible and easily performed in bed. The primary outcome measures were adherence and participation.ResultsThirty-nine ill patients, recently admitted to an acute care hospital, who were over age 70 [mean age of 82.0 (SD= 7.3)] and ambulatory prior to admission, were randomized to the resistance exercise group (19) or passive range of motion (ROM) group (20). For the resistance exercise group, participation was 71% (p = 0.004) and adherence was 63% (p = 0.020). Participation and adherence for ROM exercises was 96% and 95%, respectively.ConclusionUsing a standardized and simple exercise regimen, selected, ill, older adults in the hospital are able to comply with resistance exercise. Further studies are needed to determine if resistance exercise can prevent or treat hospital-related deterioration in mobility and function.