LEG MUSCLE ACTIVATION PATTERNS DURING SIT-TO-STAND UNDER VARIABLE COMPLIANCE SURFACES

The purpose of this study was to look if there were any differences in lower limb muscle activation patterns on various compliance surfaces during a sit-to-stand (STS) task. Previous studies have compared muscle activation patterns on stable versus unstable supporting surfaces but on the current research the surface stability was modified through four eight-way adjustable-stiffness shock absorbers mounted between two force plates creating stiffness conditions ranging from soft to very hard. Seventeen participants that were recruited randomly by a pool of volunteers performed a self-paced STS under eight surface stiffness conditions in randomized order. The mean EMG values of ten muscles during STS on various compliance surfaces were analysed and compared according under distinct phases of force profile. There were no statistically significant differences found in mean EMG of the muscles examined under different supporting surface stiffness conditions. It was found that muscle activation patterns during STS do not significantly change with variations of the surface compliance, suggesting that a STS movement skill is preprogramed, when the STS conditions are not known

Biomechanical Research in Dance: A Literature Review

The authors reviewed the literature, published from 1970 through December 2009, on biomechanical research in dance. To identify articles, the authors used search engines, including PubMed and Web of Science, five previous review articles, the Dance Medicine and Science Bibliography, and reference lists of theses, dissertations, and articles being reviewed. Any dance research articles (English language) involving the use of electromyography (EMG), forceplates, motion analysis using photography, cinematography or videography, and/or physics analysis were included. A total of 89 papers, theses/ dissertations, and abstracts were identified and reviewed, grouped by the movement concept or specialized movements being studied: alignment (n = 8), plié (8), relevé (8), passé (3), degagé (3), développé (7), rond de jambe (3), grand battement (4), arm movements (1), forward stepping (3), turns (6), elevation work (28), falls (1), and dance-specific motor strategies (6). Several recurring themes emerged from these studies: that elite dancers demonstrate different and superior motor strategies than novices or nondancers; that dancers perform differently when using a barre as opposed to without a barre, both in terms of muscle activation patterns and weight shift strategies; that while skilled dancers tend to be more consistent across multiple trials of a task, considerable variability is seen among participants, even when matched for background, years of training, body type, and other variables; and that dance teachers recommend methods of achieving movement skills that are inconsistent with optimal biomechanical function, as well as inconsistent with strategies employed by elite dancers. Measurement tools and the efficacy of study methodologies are also discussed

Biomechanical research in dance: a literature review.

The authors reviewed the literature, published from 1970 through December 2009, on biomechanical research in dance. To identify articles, the authors used search engines, including PubMed and Web of Science, five previous review articles, the Dance Medicine and Science Bibliography, and reference lists of theses, dissertations, and articles being reviewed. Any dance research articles (English language) involving the use of electromyography, forceplates, motion analysis using photography, cinematography or videography, and/or physics analysis were included. A total of 89 papers, theses/dissertations, and abstracts were identified and reviewed, grouped by the movement concept or specialized movements being studied: alignment (n = 8), plié (8), relevé (8), passé (3), degagé (3), développé (7), rond de jambe (3), grand battement (4), arm movements (1), forward stepping (3), turns (6), elevation work (28), falls (1), and dance-specific motor strategies (6). Several recurring themes emerged from these studies: that elite dancers demonstrate different and superior motor strategies than novices or nondancers; that dancers perform differently when using a barre as opposed to without a barre, both in terms of muscle activation patterns and weight shift strategies; that while skilled dancers tend to be more consistent across multiple trials of a task, considerable variability is seen among participants, even when matched for background, years of training, body type, and other variables; and that dance teachers recommend methods of achieving movement skills that are inconsistent with optimal biomechanical function, as well as inconsistent with strategies employed by elite dancers. Measurement tools and the efficacy of study methodologies are also discussed

Examination of weight transfer strategies during the execution of grand battement devant at the barre, in the center, and traveling.

The purpose of this study was to examine grand battement devant at the barre, in the center, and traveling through space. The primary focus was to consider weight transfer in three conditions: from two feet to one foot for the barre and center conditions, and from one foot to the other foot in traveling. Forty female dancers volunteered (mean age 30.0 ± 13.0 yrs) and were placed in three groups: beginner (n = 12), intermediate (n = 14), and advanced (n = 14). Data were collected with a 7-camera Vicon motion capture system using a Plug-in Gait Full Body Marker set and with two Kistler force plates. Dancers executed five grand battement devant in each of three conditions in randomized order: at the barre in 1st position, in the center in 1st position, and traveling through space. Four variables were investigated: center of gravity of the full trunk, center of gravity of the pelvis, center of gravity of the upper trunk, and center of mass. Data were analyzed in three intervals-stance to battement initiation (STN to GBI), initiation to battement peak (GBI to GBP), and peak to end (GBP to END)-and in the x-axis and y-axis. The main effect condition was significant for all four variables in both x-axis and y-axis (p<0.001). There were no significant differences for training and no significant condition X training interactions. Condition was significant for all three intervals (STN to GBI, GBI to GBP, and GBP to END) for all four variables in both axes (p<0.01). Dance educators might consider the importance of allocating sufficient time in dance practice to each of the three conditions-barre, center, and traveling-to ensure development of a variety of motor strategies for weight transfer

Electromyographic comparison of grand battement devant at the barre, in the center, and traveling.

This study examined utilization of the trunk and lower extremity muscles during grand battement devant in three conditions: at the barre (supported stationary condition in 1st position), in the center (unsupported stationary condition in 1st position), and traveling through space. Forty dancers (age 30.0 ± 13.0 yrs, height 1.63 ± 0.06 m, weight 59.0 ± 7.4 kg, and 13.9 ± 13.3 yrs of training in ballet and/or modern dance) volunteered and were placed in three skill level groups: beginner (n = 12), intermediate (n = 14), and advanced (n = 14). Dancers executed five grand battement devant in each of the three conditions in randomized order. We examined muscle activation bilaterally in eight muscles (abdominals, abductor hallucis, erector spinae, gastrocnemius, gluteus maximus, hamstrings, quadriceps, and tibialis anterior) using surface electromyography, a three-dimensional video biomechanical tracking system to identify events, and force plates. All data were analyzed in four events: stance, initiation, peak, and end. Analysis was done using a linear mixed effects regression model with condition, event, muscle, level, and side as the fixed effects, and subject as the random effect. There were significant effects for muscle x event x condition (p<0.01) and for level x side x muscle (p<0.01). Muscle use varied according to the combination of event and condition that was executed, and these differences were also influenced by the level of training of the dancer and the side of the body used. It is recommended that dance educators consider the importance of allocating sufficient time to each of the three conditions (barre, center, and traveling) to ensure development of a variety of motor strategies and muscle activation levels for dance practice

Development of a portable anchored dynamometer for collection of maximal voluntary isometric contractions in biomechanics research on dancers

Surface electromyography (sEMG) has been used in dance medicine research since the 1970s, but normalization procedures are not consistently employed in the field. The purpose of this project was to develop a portable anchored dynamometer (PAD) specifically for dance-related research. Due to the limited studies in the dance research literature using normalization procedures for sEMG data, a review of the procedures used in the exercise science literature was conducted. A portable anchored dynamometer was then developed and tested with dancers, using methods validated in previous literature. We collected sEMG maximum voluntary isometric contractions (MVIC, mV) from 10 female dancers (mean age 31.0 ± 15 yrs, mean height 163 ± 7.6 cm, mean weight 57.6 ± 6.9 kg, and 17.0 ± 13.9 yrs of training in ballet and/or modern dance) over three trials (5 sec each) for eight muscles bilaterally (quadriceps, tibialis anterior, abductor hallucis, gastrocnemius, hamstrings, gluteus maximus, erector spinae, and rectus abdominus). Consistency of data and feedback from dancers suggest that this dance-specific portable anchored dynamometer is effective for future sEMG studies in dance research