Dancers with non-specific low back pain have less lumbar movement smoothness than healthy dancers.

BACKGROUND: Ballet is a highly technical and physically demanding dance form involving extensive end-range lumbar movements and emphasizing movement smoothness and gracefulness. A high prevalence of non-specific low back pain (LBP) is found in ballet dancers, which may lead to poor controlled movement and possible pain occurrence and reoccurrence. The power spectral entropy of time-series acceleration is a useful indicator of random uncertainty information, and a lower value indicates a greater smoothness or regularity. The current study thus applied a power spectral entropy method to analyze the movement smoothness in lumbar flexion and extension in healthy dancers and dancers with LBP, respectively. METHOD: A total of 40 female ballet dancers (23 in the LBP group and 17 in the control group) were recruited in the study. Repetitive end-range lumbar flexion and extension tasks were performed and the kinematic data were collected using a motion capture system. The power spectral entropy of the time-series acceleration of the lumbar movements was calculated in the anterior-posterior (AP), medial-lateral (ML), vertical (VT), and three-directional (3D) vectors. The entropy data were then used to conduct receiver operating characteristic curve analyses to evaluate the overall distinguishing performance and thus cutoff value, sensitivity, specificity, and area under the curve (AUC) were calculated. RESULTS: The power spectral entropy was significantly higher in the LBP group than the control group in the 3D vector in both lumbar flexion and lumber extension (flexion: p = 0.005; extension: p < 0.001). In lumbar extension, the AUC in the 3D vector was 0.807. In other words, the entropy provides an 80.7% probability of distinguishing between the two groups (i.e., LBP and control) correctly. The optimal cutoff entropy value was 0.5806 and yielded a sensitivity of 75% and specificity of 73.3%. In lumbar flexion, the AUC in the 3D vector was 0.777, and hence the entropy provided a probability of 77.7% of distinguishing between the two groups correctly. The optimal cutoff value was 0.5649 and yielded a sensitivity of 90% and a specificity of 73.3%. CONCLUSIONS: The LBP group showed significantly lower lumbar movement smoothness than the control group. The lumbar movement smoothness in the 3D vector had a high AUC and thus provided a high differentiating capacity between the two groups. It may therefore be potentially applied in clinical contexts to screen dancers with a high risk of LBP.

Fatigue-Induced Changes in Movement Pattern and Muscle Activity During Ballet Releve on Demi-Pointe.

Fatigue in ballet dancers may lead to injury, particularly in the lower extremities. However, few studies have investigated the effects of fatigue on ballet dancers' performance and movement patterns. Thus, the current study examines the effect of fatigue on the balance, movement pattern, and muscle activities of the lower extremities in ballet dancers. Twenty healthy, female ballet dancers performed releve on demi-pointe before and after fatigue. The trajectory of the whole body movement and the muscle activities of the major lower extremity muscles were recorded continuously during task performance. The results show that fatigue increases the medial-lateral center of mass (COM) displacement and hip and trunk motion, but decreases the COM velocity and ankle motion. Moreover, fatigue reduces the activities of the hamstrings and tibialis anterior, but increases that of the soleus. Finally, greater proximal hip and trunk motions are applied to compensate for the effects of fatigue, leading to a greater COM movement. Overall, the present findings show that fatigue results in impaired movement control and may therefore increase the risk of dance injury.

Fatigue-Induced Changes in Movement Pattern and Muscle Activity During Ballet Releve on Demi-Pointe.

Fatigue in ballet dancers may lead to injury, particularly in the lower extremities. However, few studies have investigated the effects of fatigue on ballet dancers' performance and movement patterns. Thus, the current study examines the effect of fatigue on the balance, movement pattern, and muscle activities of the lower extremities in ballet dancers. Twenty healthy, female ballet dancers performed releve on demi-pointe before and after fatigue. The trajectory of the whole body movement and the muscle activities of the major lower extremity muscles were recorded continuously during task performance. The results show that fatigue increases the medial-lateral center of mass (COM) displacement and hip and trunk motion, but decreases the COM velocity and ankle motion. Moreover, fatigue reduces the activities of the hamstrings and tibialis anterior, but increases that of the soleus. Finally, greater proximal hip and trunk motions are applied to compensate for the effects of fatigue, leading to a greater COM movement. Overall, the present findings show that fatigue results in impaired movement control and may therefore increase the risk of dance injury.

The movement patterns used to rise from a supine position by children with developmental delay and age-related differences in these.

The purposes of this study were to determine (1) movement patterns and strategies of children with mild to moderate developmental delay (DD) used to rise up and how they differ from those used by age-matched children with typical development (TD), (2) whether the movement patterns differ with age in children with DD, and (3) to determine the developmental sequences for the UE, AX and LE in children with DD and whether they are different from those used by children with TD. Sixty six children with TD and 31 children with DD aged two to six years were recruited. Peabody Developmental Motor Scale II (PDMS-2) was used to determine the motor performance level. The participants were recorded during rising for at least five repetitions. Two trained pediatric physical therapists viewed each video recording and classified the movement patterns of the upper extremities (UE), trunk/axial (AX) and lower extremities (LE) regions using descriptive categories developed by previous researchers. The DD and TD groups were further divided into four subgroups each using a one-year interval. The percentage of occurrence of the each UE, AX and LE movement was determined and compared across subgroups, and between each age-matched pair of TD and DD groups. The results demonstrated that the participants in the TD group clearly followed the proposed developmental sequence and the children with DD followed the developmental sequences but with different maturation speeds and greater variability, especially at the age of three to five years. The most common movement patterns used by the children in each of the DD subgroups were at least one developmental categorical pattern behind those used by the age-matched children with TD before five years old, except for the LE region. In the DD group, the movement patterns had moderate to high correlation with the child's motor performance level, indicating that the children with better motor performances used more developmentally advanced patterns in comparison with those with lower scores. However, besides motor maturity, numerous other intrinsic/extrinsic factors may affect the child's performance of this task. The information obtained in this study would assist therapists when working with the children with DD, so that they can provide individualized treatment rather than guiding all such children toward a single, mature pattern.

Effects of age and gender on dynamic stability during stair descent.

OBJECTIVE: To determine the effects of age and sex and their interaction effects on dynamic postural stability during stair descent. DESIGN: Cross sectional. SETTING: Laboratory. PARTICIPANTS: Healthy younger adults (N=28) and healthy older adults (N=21). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Spatiotemporal gait parameters, displacement of center of mass (COM), instantaneous velocity of the COM, divergence between vertical projection of the COM, and center of pressure (COP). RESULTS: Interaction effects of age and sex were found in stride duration, COM displacement, and instantaneous velocity of the COM in the mediolateral direction. Older adults demonstrated longer stride duration with shorter double-limb stance and longer single-limb stance during stair descent. Women have significantly longer stride duration than men. The effects of sex and age were significant in the data normalized by height. Older adults and women demonstrated larger peak-to-peak COM displacement, peak instantaneous velocity of the COM, and COM-COP divergence than the younger individuals and men, respectively. Peak instantaneous velocity of the COM was significant different in most pairwise comparisons, but the COM-COP divergence was significantly different in several comparisons. CONCLUSIONS: This study examined the COM and COP parameters to quantify dynamic stability during stair descent across sex and age. Although older women descended stairs successfully, they demonstrated differences in control of instantaneous velocity of the COM compared with the other participants. Dynamic instability could be detected by examining the control of instantaneous velocity of the COM. In developing a better understanding of the balance control of stair descent in healthy older adults, aging patients with various pathologies can be better assessed, appropriately treated, and provided with proper assistive devices.

The intra- and inter-rater reliability of component analysis of rise from supine in the children with typical development and developmental delay.

The purpose of this study was to determine the intra- and inter-rater reliability of classifying the movement patterns of rising from supine to stand in the children with typical development (TD) and mild to moderate developmental delay (DD). Sixty-eight children with TD and 20 children with DD aged 2 through 6 years were videotaped during rising. Two trained pediatric physical therapists independently viewed each videotape and classified the movement patterns of upper extremities (UE), trunk/axial (AX) and lower extremities (LE) regions using descriptive categories developed by previous researchers. Kappa statistic and average percentage of agreement were calculated to determine reliability. The average agreement rate of intra-rater ranged from 90% to 97% in TD group for three regions, and 79% to 89% in DD group; the agreement rate between raters ranged from 82% to 95% in TD group for three regions, and 71% to 87% in DD group. Using kappa statistic guidelines, high intra- and inter-rater reliabilities (k>0.81) were found in TD group, except inter-rater reliability for LE. Substantial intra- and inter-reliabilities (0.61

A comparison of ballet dancers with different level of experience in performing single-leg stance on retiré position.

The purpose of the current study was to evaluate the postural stability of single-leg standing on the retiré position in ballet dancers having three different levels of skill. Nine superior experienced female ballet dancers, 9 experienced, and 12 novice dancers performed single-leg standing in the retiré position. The parameters of center of pressure (COP) in the anterior-posterior and medial-lateral directions and the maximum distance between COP and the center of mass (COM) were measured. The inclination angles of body segments (head, torso, and supporting leg) in the frontal plane were also calculated. The findings showed that the novice dancers had a trend of greater torso inclination angles than the experienced dancers but that the superior experienced dancers had greater maximum COM-COP distance in the anterior-posterior direction. Furthermore, both experienced and novice dancers had better balance when standing on the nondominant leg, whereas the superior experienced dancers had similar postural stability between legs. Based on the findings, ballet training should put equal focus on both legs and frontal plane control (medial-lateral direction) should be integrated to ballet training program.

The effect of cane use method on center of mass displacement during stair ascent.

The aim of the study was to examine the effect of forward and lateral cane placement on displacement of whole body center of mass (COM) and spatial relationship between COM and the cane during stair ascent (SA) in healthy adults. The data were obtained using three-dimensional motion analysis while ascending stairs non-reciprocally with following methods: (1) dominant foot stepped up first, then the opposite foot without a cane (NC); (2) forward placement of a quadricane followed by the ipsilateral foot, then contralateral foot (FCI); (3) forward cane placement followed by the contralateral foot, then ipsilateral foot (FCC); (4) ipsilateral foot stepping up first, followed by the contralateral foot, then the cane (LCI); (5) contralateral foot stepping up, followed by the ipsilateral foot, then the cane (LCC). The results indicated that the cane placement had significant effect on the medial-lateral (ML) COM displacement and the kinematics of the trunk. Lateral cane placement requires greater trunk extension and side-flexion. The major differences between ipsilateral and contralateral cane use are the motions at frontal and transverse planes in which the COM displacement in ML direction is larger in ipsilateral cane use. The COM displacement in ML direction is larger in ipsilateral use of cane (LCI and FCI). The results of this study may help clinicians better understand the possible nature of balance control in patients who ascend stairs with a cane, and suggest that the method of cane placement should be taken into consideration by clinicians when teaching the cane user to ascend stairs.

The dynamic balance of the children with cerebral palsy and typical developing during gait Part II: Instantaneous velocity and acceleration of COM and COP and their relationship.

As a companion research subsequent to analyzing displacement of center of mass (COM) and center of pressure (COP) in Part I, the purposes of this study were to quantify dynamic stability using magnitudes and patterns of instantaneous velocity and acceleration of COM and COP of the children with cerebral palsy (CP) during walking, and compare the data with those of the typically developing (TD) children. The instantaneous velocity and acceleration of COM and COP were acquired by calculating the first and second derivatives of displacement data presented in Part I. Velocity and acceleration of COM and COP were normalized by each participant's leg length to eliminate the influence of individual's stature. The results indicate that the preferred walking speed is significantly higher in TD groups than hemiplegic group (Hemi) and diplegic group (Di). The peak values of instantaneous velocity and acceleration of COM in vertical, medio-lateral (ML) and antero-posterior (AP) directions and velocity and acceleration of COP in ML direction were significantly higher in Di group than TD group. Both CP groups showed great variability in COM and COP parameters. Therefore, although Di group demonstrated higher peak values than Hemi group, the only significant difference between two groups was instantaneous COP velocity in ML direction. The findings of this study suggest that this assessment may be of value for research or clinical evaluation of dynamic balance dysfunction during walking and provide comparisons and insights for specific treatments or surgical interventions for the children with CP.

The dynamic balance of the children with cerebral palsy and typical developing during gait. Part I: Spatial relationship between COM and COP trajectories.

Analysis of the COM or COP movement has been a simplified method to illustrate the balance disorders in static stance and gait, but has its limitation when examined alone. Dynamic stability of 32 children with cerebral palsy (CP) was examined and compared with 10 typically developing (TD) children by measuring the displacement of center of mass (COM) and center of pressure (COP) and their spatial relationship. The children with CP were further divided into two groups based on topographical involvement, hemiplegia (Hemi) and diplegia (Di). The participants walked with their preferred speed at least 5 successful trials on a walkway with two force plates mounted in the middle. An eight-camera motion analysis was used to capture 26 reflective markers secured at the bony landmarks of the participant. The data obtained from motion analysis and force plates was used to calculate COM and COP. The results showed either of two CP groups demonstrated significantly greater peak-to-peak COM and COP displacement in medio-lateral (ML) and lower peak-to-peak COM and COP displacement in anterio-posterior (AP) direction than TD group. The root mean square (RMS) of COM-COP divergence of Hemi and Di groups were higher than that of TD group in AP and ML direction, but only the difference in ML direction was significant. Present study demonstrates that COM-COP divergence can characterize the dynamic balance of the CP children in walking, and thus assist in comparing and differentiating balance patterns.

Gait and kinematics of the trunk and lower extremities in stair ascent using quadricane in healthy subjects.

Different cane placement methods require different gait patterns and ranges of motion either at the trunk or lower extremities. The aim of this study was to examine the effect of cane placement on body biomechanics in stair ascent (SA) in 16 healthy adults (9 women, 7 men) aged 27.2+/-3.2 years old. The height and weight of the women and men were 160.8+/-5.4 cm and 54.1+/-8.1 kg, and 170.8+/-3.9 cm and 69.6+/-5.6 kg, respectively. Three-dimensional motion data were collected in non-reciprocally SA associated with following methods: (1) dominant foot stepped up first, then the opposite foot without a cane (NC); (2) forward placement of a quadricane followed by the ipsilateral foot, then contralateral foot (FCI); (3) forward cane placement followed by the contralateral foot, then ipsilateral foot (FCC); (4) ipsilateral foot stepping up first, followed by the contralateral foot and the cane (LCI); (5) contralateral foot stepping up, followed by the ipsilateral foot and cane (LCC). LCI and LCC were considered as lateral cane placement. Temporal gait parameters, kinematics of the trunk and lower extremities were calculated. The results indicate that the cane placement had significant effect on the kinematics of the trunk and lower extremities. The main differences between forward and lateral cane placement were flexion and side flexion of the trunk, and flexion of the leading and opposite hip and knee. Hip rotation and abduction, and ankle plantar and dorsiflexion were different between contralateral and ipsilateral cane placements.

Kinematics and kinetics of the lower extremities of young and elder women during stairs ascent while wearing low and high-heeled shoes.

The effect of the heel height on the temporal, kinematic and kinetic parameters was investigated in 16 young and 11 elderly females. Kinematic and kinetic data were collected when the subjects ascended stairs with their preferred speed in two conditions: wearing low-heeled shoes (LHS), and high-heeled shoes (HHS). The younger adults showed more adjustments in forces and moments at the knee and hip in frontal and transverse planes. Besides a few significantly changes in joint forces and moments, the elder group demonstrated longer cycle duration and double stance phase, larger trunk sideflexion and hip internal rotation, less hip adduction while wearing HHS. Most differences in joint motions between two groups were found at the hip and knee either in LHS or HHS condition. Instead, the differences in moment occurred at the hip joint and only in HHS. The interaction of the heel height and age showed the influences of heel height on trunk rotation, hip abduction/adduction, and knee and hip force and moment at the frontal plane depended on age. These phenomena suggest that younger and elderly women adapt their gait and postural control differently during stair ascent (SA) while wearing HHS.