Action Observation and Acquired Motor Skills: An fMRI Study with Expert Dancers

When we observe someone performing an action, do our brains simulate making that action? Acquired motor skills offer a unique way to test this question, since people differ widely in the actions they have learned to perform. We used functional magnetic resonance imaging to study differences in brain activity between watching an action that one has learned to do and an action that one has not, in order to assess whether the brain processes of action observation are modulated by the expertise and motor repertoire of the observer. Experts in classical ballet, experts in capoeira and inexpert control subjects viewed videos of ballet or capoeira actions. Comparing the brain activity when dancers watched their own dance style versus the other style therefore reveals the influence of motor expertise on action observation. We found greater bilateral activations in premotor cortex and intraparietal sulcus, right superior parietal lobe and left posterior superior temporal sulcus when expert dancers viewed movements that they had been trained to perform compared to movements they had not. Our results show that this 'mirror system' integrates observed actions of others with an individual's personal motor repertoire, and suggest that the human brain understands actions by motor simulation.

Seeing or Doing? Influence of Visual and Motor Familiarity in Action Observation

The human brain contains specialized circuits for observing and understanding actions. Previous studies have not distinguished whether this "mirror system" uses specialized motor representations or general processes of visual inference and knowledge to understand observed actions. We report the first neuroimaging study to distinguish between these alternatives. Purely motoric influences on perception have been shown behaviorally, but their neural bases are unknown. We used fMRI to reveal the neural bases of motor influences on action observation. We controlled for visual and knowledge effects by studying expert dancers. Some ballet moves are performed by only one gender. However, male and female dancers train together and have equal visual familiarity with all moves. Male and female dancers viewed videos of gender-specific male and female ballet moves. We found greater premotor, parietal, and cerebellar activity when dancers viewed moves from their own motor repertoire, compared to opposite-gender moves that they frequently saw but did not perform. Our results show that mirror circuits have a purely motor response over and above visual representations of action. We understand actions not only by visual recognition, but also motorically. In addition, we confirm that the cerebellum is part of the action observation network.

Hamilton AF, Grafton ST. Building a motor simulation de novo: observation of dance by dancers

Research on action simulation identifies brain areas that are active while imagining or performing simple overlearned actions. Are areas engaged during imagined movement sensitive to the amount of actual physical practice? In the present study, participants were expert dancers who learned and rehearsed novel, complex whole-body dance sequences 5 h a week across 5 weeks. Brain activity was recorded weekly by fMRI as dancers observed and imagined performing different movement sequences. Half these sequences were rehearsed and half were unpracticed control movements. After each trial, participants rated how well they could perform the movement. We hypothesized that activity in premotor areas would increase as participants observed and simulated movements that they had learnt outside the scanner. Dancers' ratings of their ability to perform rehearsed sequences, but not the control sequences, increased with training. When dancers observed and simulated another dancer's movements, brain regions classically associated with both action simulation and action observation were active, including inferior parietal lobule, cingulate and supplementary motor areas, ventral premotor cortex, superior temporal sulcus and primary motor cortex. Critically, inferior parietal lobule and ventral premotor activity was modulated as a function of dancers' ratings of their own ability to perform the observed movements and their motor experience. These data demonstrate that a complex motor resonance can be built de novo over 5 weeks of rehearsal. Furthermore, activity in premotor and parietal areas during action simulation is enhanced by the ability to execute a learned action irrespective of stimulus familiarity or semantic label.

Feeling the Beat: Movement Influences Infant Rhythm Perception

We hear the melody in music, but we feel the beat. We demonstrate that the perception of musical rhythm is a multisensory experience in infancy. In particular, movement of the body, by bouncing on every second versus every third beat of an ambiguous auditory rhythm pattern, influences whether that auditory rhythm pattern is encoded in duple form (a march) or in triple form (a waltz). Visual information is not necessary for the effect, indicating that it likely reflects a strong, early-developing interaction between auditory and vestibular information in the human nervous system.

Effects of dance on movement control in Parkinson's disease: a comparison of Argentine tango and American ballroom

OBJECTIVE

The basal ganglia may be selectively activated during rhythmic, metered movement such as tango dancing, which may improve motor control in individuals with Parkinson's disease. Other partner dances may be more suitable and preferable for those with Parkinson's disease. The purpose of this study was to compare the effects of tango, waltz/foxtrot and no intervention on functional motor control in individuals with Parkinson's disease.

DESIGN

This study employed a randomized, between- notsubject, prospective, repeated measures design.

SUBJECTS/PATIENTS

Fifty-eight people with mild-moderate Parkinson's disease participated.

METHODS

Participants were randomly assigned to tango, waltz/foxtrot or no intervention (control) groups. Those in the dance groups attended 1-h classes twice a week, completing 20 lessons in 13 weeks. Balance, functional mobility, forward and backward walking were evaluated before and after the intervention.

RESULTS

Both dance groups improved more than the control group, which did not improve. The tango and waltz/foxtrot groups improved significantly on the Berg Balance Scale, 6-minute walk distance, and backward stride length. The tango group improved as much or more than those in the waltz/foxtrot group on several measures.

CONCLUSION

Tango may target deficits associated with Parkinson's disease more than waltz/foxtrot, but both dances may benefit balance and locomotion.

Physical activity in the prevention and amelioration of osteoporosis in women : interaction of mechanical, hormonal and dietary factors

Osteoporosis is a serious health problem that diminishes quality of life and levies a financial burden on those who fear and experience bone fractures. Physical activity as a way to prevent osteoporosis is based on evidence that it can regulate bone maintenance and stimulate bone formation including the accumulation of mineral, in addition to strengthening muscles, improving balance, and thus reducing the overall risk of falls and fractures. Currently, our understanding of how to use exercise effectively in the prevention of osteoporosis is incomplete. It is uncertain whether exercise will help accumulate more overall peak bone mass during childhood, adolescence and young adulthood. Also, the consistent effectiveness of exercise to increase bone mass, or at least arrest the loss of bone mass after menopause, is also in question. Within this framework, section 1 introduces mechanical characteristics of bones to assist the reader in understanding their responses to physical activity. Section 2 reviews hormonal, nutritional and mechanical factors necessary for the growth of bones in length, width and mineral content that produce peak bone mass in the course of childhood and adolescence using a large sample of healthy Caucasian girls and female adolescents for reference. Effectiveness of exercise is evaluated throughout using absolute changes in bone with the underlying assumption that useful exercise should produce changes that approximate or exceed the absolute magnitude of bone parameters in a healthy reference population. Physical activity increases growth in width and mineral content of bones in girls and adolescent females, particularly when it is initiated before puberty, carried out in volumes and at intensities seen in athletes, and accompanied by adequate caloric and calcium intakes. Similar increases are seen in young women following the termination of statural growth in response to athletic training, but not to more limited levels of physical activity characteristic of longitudinal training studies. After 9-12 months of regular exercise, young adult women often show very small benefits to bone health, possibly because of large subject attrition rates, inadequate exercise intensity, duration or frequency, or because at this stage of life accumulation of bone mass may be at its natural peak. The important influence of hormones as well as dietary and specific nutrient abundance on bone growth and health are emphasised, and premature bone loss associated with dietary restriction and estradiol withdrawal in exercise-induced amenorrhoea is described. In section 3, the same assessment is applied to the effects of physical activity in postmenopausal women. Studies of postmenopausal women are presented from the perspective of limitations of the capacity of the skeleton to adapt to mechanical stress of exercise due to altered hormonal status and inadequate intake of specific nutrients. After menopause, effectiveness of exercise to increase bone mineral depends heavily on adequate availability of dietary calcium. Relatively infrequent evidence that physical activity prevents bone loss or increases bone mineral after menopause may be a consequence of inadequate calcium availability or low intensity of exercise in training studies. Several studies with postmenopausal women show modest increases in bone mineral toward the norm seen in a healthy population in response to high-intensity training. Physical activities continue to stimulate increases in bone diameter throughout the lifespan. These exercise-stimulated increases in bone diameter diminish the risk of fractures by mechanically counteracting the thinning of bones and increases in bone porosity. Seven principles of bone adaptation to mechanical stress are reviewed in section 4 to suggest how exercise by human subjects could be made more effective. They posit that exercise should: (i) be dynamic, not static; (ii) exceed a threshold intensity; (iii) exceed a threshold strain frequency; (iv) be relatively brief but intermittent; (v) impose an unusual loading pattern on the bones; (vi) be supported by unlimited nutrient energy; and (vii) include adequate calcium and cholecalciferol (vitamin D3) availability.

Bone mineral density in female athletes representing sports with different loading characteristics of the skeleton

To address the hypothesis that osteogenic effect of physical loading increases with increasing strain rates and peak forces, we examined 59 competitive Finnish female athletes (representing three sports with different skeletal loading characteristics), physically active referents (they reported an average of five various types of exercise sessions per week), and sedentary referents (two sessions per week) using dual energy X-ray absorptiometry. The measured anatomic sites were at the lumbar spine, femoral neck, distal femur, patella, proximal tibia, calcaneus, and distal radius. The athlete group consisted of aerobic dancers (N = 27), squash players (N = 18), and speed skaters (N = 14). The squash players had the highest values for weight-adjusted bone mineral density (BMD) at the lumbar spine (13.8% p < 0.001 as compared with the sedentary reference group), femoral neck (16.8%, p < 0.001), proximal tibia (12.6%, p < 0.001) and calcaneus (18.5%, p < 0.001). Aerobic dancers and speed skaters also had significantly higher BMD values at the loaded sites than the sedentary reference group, the difference ranging from 5.3% to 13.5%. The physically active referents' BMD values did not differ from those of the sedentary referents at any site. The results support the concept that training, including high strain rates in versatile movements and high peak forces, is more effective in bone formation than training with a large number of low-force repetitions.

The Neural Basis of Human Dance

Human dance was investigated with positron emission tomography to identify its systems-level organization. Three core aspects of dance were examined: entrainment, meter and patterned movement. Amateur dancers performed small-scale, cyclically repeated tango steps on an inclined surface to the beat of tango music, without visual guidance. Entrainment of dance steps to music, compared to self-pacing of movement, was supported by anterior cerebellar vermis. Movement to a regular, metric rhythm, compared to movement to an irregular rhythm, implicated the right putamen in the voluntary control of metric motion. Spatial navigation of leg movement during dance, when controlling for muscle contraction, activated the medial superior parietal lobule, reflecting proprioceptive and somatosensory contributions to spatial cognition in dance. Finally, additional cortical, subcortical and cerebellar regions were active at the systems level. Consistent with recent work on simpler, rhythmic, motor-sensory behaviors, these data reveal the interacting network of brain areas active during spatially patterned, bipedal, rhythmic movements that are integrated in dance.

The Dancer as a Performing Athlete

The physical demands placed on dancers from current choreography and performance schedules make their physiology and fitness just as important as skill development. However, even at the height of their professional careers, dancers' aerobic power, muscular strength, muscular balance, bone and joint integrity are the 'Achilles heels' of the dance-only selection and training system. This partly reflects the unfounded view, shared by sections of the dance world, that any exercise training that is not directly related to dance would diminish dancers' aesthetic appearances. Given that performing dance itself elicits only limited stimuli for positive fitness adaptations, it is not surprising that professional dancers often demonstrate values similar to those obtained from healthy sedentary individuals of comparable age in key fitness-related parameters. In contrast, recent data on male and female dancers revealed that supplementary exercise training can lead to improvements of such fitness parameters and reduce incidents of dance injuries, without interfering with key artistic and aesthetic requirements. It seems, however, that strict selection and training regimens have succeeded in transforming dance to an activity practised by individuals who have selectively developed different flexibility characteristics compared with athletes. Bodyweight targets are normally met by low energy intakes, with female dance students and professional ballerinas reported to consume below 70% and 80% of the recommended daily allowance of energy intake, respectively, while the female athlete 'triad' of disordered eating, amenorrhoea and osteoporosis is now well recognised and is seen just as commonly in dancers. An awareness of these factors will assist dancers and their teachers to improve training techniques, to employ effective injury prevention strategies and to determine better physical conditioning. However, any change in the traditional training regimes must be approached cautiously to ensure that the aesthetic content of the dance is not affected by new training techniques. Since physiological aspects of performing dance have been viewed primarily in the context of ballet, further scientific research on all forms of dance is required.

H-reflexes are smaller in dancers from The Royal Danish Ballet than in well-trained athletes

The size of the maximal H-reflex (Hmax) was measured at rest and expressed as a percentage of the maximal M-response (Mmax) in 17 untrained subjects, 27 moderately trained subjects, 19 well-trained subjects and 7 dancers from the Royal Danish Ballet. The Hmax/Mmax was significantly larger in the moderately and well-trained subjects than in the untrained subjects but smaller in the ballet dancers. It is therefore suggested that both the amount and the type of habitual activity may influence the excitability of spinal reflexes.

Dance training is superior to repetitive physical exercise in inducing brain plasticity in the elderly

Animal research indicates that a combination of physical activity and sensory enrichment has the largest and the only sustaining effect on adult neuroplasticity. Dancing has been suggested as a human homologue to this combined intervention as it poses demands on both physical and cognitive functions. For the present exploratory study, we designed an especially challenging dance program in which our elderly participants constantly had to learn novel and increasingly difficult choreographies. This six-month-long program was compared to conventional fitness training matched for intensity. An extensive pre/post-assessment was performed on the 38 participants (63-80 y), covering general cognition, attention, memory, postural and cardio-respiratory performance, neurotrophic factors and-most crucially-structural MRI using an exploratory analysis. For analysis of MRI data, a new method of voxel-based morphometry (VBM) designed specifically for pairwise longitudinal group comparisons was employed. Both interventions increased physical fitness to the same extent. Pronounced differences were seen in the effects on brain volumes: Dancing compared to conventional fitness activity led to larger volume increases in more brain areas, including the cingulate cortex, insula, corpus callosum and sensorimotor cortex. Only dancing was associated with an increase in plasma BDNF levels. Regarding cognition, both groups improved in attention and spatial memory, but no significant group differences emerged. The latter finding may indicate that cognitive benefits may develop later and after structural brain changes have taken place. The present results recommend our challenging dance program as an effective measure to counteract detrimental effects of aging on the brain.

A cognitive-motor intervention using a dance video game to enhance foot placement accuracy and gait under dual task conditions in older adults: a randomized controlled trial

BACKGROUND

Computer-based interventions have demonstrated consistent positive effects on various physical abilities in older adults. This study aims to compare two training groups that achieve similar amounts of strength and balance exercise where one group receives an intervention that includes additional dance video gaming. The aim is to investigate the different effects of the training programs on physical and psychological parameters in older adults.

METHODS

Thirty-one participants (mean age ± SD: 86.2 ± 4.6 years), residents of two Swiss hostels for the aged, were randomly assigned to either the dance group (n = 15) or the control group (n = 16). The dance group absolved a twelve-week cognitive-motor exercise program twice weekly that comprised progressive strength and balance training supplemented with additional dance video gaming. The control group performed only the strength and balance exercises during this period. Outcome measures were foot placement accuracy, gait performance under single and dual task conditions, and falls efficacy.

RESULTS

After the intervention between-group comparison revealed significant differences for gait velocity (U = 26, P = .041, r = .45) and for single support time (U = 24, P = .029, r = .48) during the fast walking dual task condition in favor of the dance group. No significant between-group differences were observed either in the foot placement accuracy test or in falls efficacy.

CONCLUSIONS

There was a significant interaction in favor of the dance video game group for improvements in step time. Significant improved fast walking performance under dual task conditions (velocity, double support time, step length) was observed for the dance video game group only. These findings suggest that in older adults a cognitive-motor intervention may result in more improved gait under dual task conditions in comparison to a traditional strength and balance exercise program.

TRIAL REGISTRATION

This trial has been registered under ISRCTN05350123 (www.controlled-trials.com)

Dynamic patterns of postural sway in ballet dancers and track athletes

We compared the variability and spatiotemporal profile of postural sway of trained ballet dancers to college varsity track athletes under variations in the availability of vision and rigidity of the support surface. We found no differences between the groups according to the variability measures, but variability increased for both groups with eyes closed and on a foam surface. Recurrence quantification analysis revealed that the postural sway of dancers was less regular (lower recurrence), less stable (lower maxline), less complex (lower entropy), and more stationary (lower absolute trend) than that of track athletes. Dancers, possibly as a result of focused balance training, exhibited different dynamic patterns of postural sway.

Visual contribution to self-induced body sway frequencies and visual perception of male professional dancers

We studied the degree of dependence on vision, for postural control and for perception, among male adult dancers and untrained subjects. First, body sways were analyzed on a free seesaw platform. Fast Fourier transform processing allowed spectral frequency analysis of the platform sways recorded by an accelerometer. Secondly, a visual dependence test, the rod and frame test (RFT) was used. Professional dancers were significantly more stable and less dependent on vision for postural control and for perception than untrained subjects. Presumably, professional dance training strengthens the accuracy of proprioceptive inputs and shifts sensorimotor dominance from vision to proprioception. For the dancers, there was interaction between the RFT visual dependence and the visual control of posture: the less visual-dependent they were for the RFT, the more stable they were in dynamic balance conditions.

The role of peer social network factors and physical activity in adolescent girls

OBJECTIVE

To study the relationship between peer-related physical activity (PA) social networks and the PA of adolescent girls.

METHODS

Cross-sectional, convenience sample of adolescent girls. Mixed-model linear regression analyses to identify significant correlates of self-reported PA while accounting for correlation of girls in the same school.

RESULTS

Younger girls were more active than older girls. Most activity-related peer social network items were related to PA levels. More PA with friends was significantly related to self-reported PA in multivariate analyses.

CONCLUSIONS

Frequency of PA with friends was an important correlate of PA among the peer network variables for adolescent girls.

Motor imagery of walking following training in locomotor attention. The effect of ‘the tango lesson’

The hypothesis of this study is that focusing attention on walking motor schemes could modify sensorimotor activation of the brain. Indeed, gait is a learned automated process, mostly regulated by subcortical and spinal structures. We examined the functional changes in the activity of the cerebral areas involved in locomotor imagery tasks, before and after one week of training consisting of physical and mental practice. The aim of the training was to focus the subject's conscious attention on the movements involved in walking. In our training, subjects were asked to perform basic tango steps, which require specific ways of walking; each tango lesson ended with motor imagery training of the performed steps. The results show that training determines an expansion of active bilateral motor areas during locomotor imagery. This finding, together with a reduction of visuospatial activation in the posterior right brain, suggests a decreased role of visual imagery processes in the post-training period in favor of motor-kinesthetic ones.

Overuse injuries in classical ballet

Successful management of classical ballet dancers with overuse injuries requires an understanding of the art form, precise knowledge of anatomy and awareness of certain conditions. Turnout is the single most fundamental physical attribute in classical ballet and 'forcing turnout' frequently contributes to overuse injuries. Common presenting conditions arising from the foot and ankle include problems at the first metatarsophalangeal joint, second metatarsal stress fractures, flexor hallucis longus tendinitis and anterior and posterior ankle impingement syndromes. Persistent shin pain in dancers is often due to chronic compartment syndrome, stress fracture of the posteromedial or anterior tibia. Knee pain can arise from patellofemoral syndrome, patellar tendon insertional pathologies, or a combination of both. Hip and back problems are also prevalent in dancers. To speed injury recovery of dancers, it is important for the sports medicine team to cooperate fully. This permits the dancer to benefit from accurate diagnosis, technique correction where necessary, the full range of manual therapies to joint and soft tissue, appropriate strengthening programmes and maintenance of dance fitness during any time out of class with Pilates-based exercises and nutrition advice. Most overuse ballet conditions respond well to a combination of conservative therapies. Those dancers that do require surgical management still depend heavily on ballet-specific rehabilitation for a complete recovery.

Honeybee colonies achieve fitness through dancing

The honeybee dance language, in which foragers perform dances containing information about the distance and direction to food sources, is the quintessential example of symbolic communication in non-primates. The dance language has been the subject of controversy, and of extensive research into the mechanisms of acquiring, decoding and evaluating the information in the dance. The dance language has been hypothesized, but not shown, to increase colony food collection. Here we show that colonies with disoriented dances (lacking direction information) recruit less effectively to syrup feeders than do colonies with oriented dances. For colonies foraging at natural sources, the direction information sometimes increases food collected, but at other times it makes no difference. The food-location information in the dance is presumably important when food sources are hard to find, variable in richness and ephemeral. Recruitment based simply on arousal of foragers and communication of floral odour, as occurs in honeybees, bumble bees and some stingless bees, can be equally effective under other circumstances. Clarifying the condition-dependent payoffs of the dance language provides new insight into its function in honeybee ecology.

Evaluation of the Energy Cost of Playing a Dance Simulation Video Game in Overweight and Non-Overweight Children and Adolescents

The purpose of this study was to determine if there were any differences in the submaximal energy cost of movement between overweight (OW) and non-overweight (NO) children while playing a dance simulation video game, Dance Dance Revolution (DDR) and to determine if the cardiorespiratory measures obtained while playing the game met the American College of Sports Medicine (ACSM) recommendations for developing and maintaining cardiorespiratory fitness. Twenty-two children and adolescents (10 OW vs. 12 NO) participated in the study. Cardiorespiratory measurements were taken both during a maximal treadmill walking test and during a 12-minute Dance Dance Revolution protocol. The average absolute VO2 (OW: 917.1 +/- 257.1 vs. 590.6 +/- 147.9 mL . min (-1)) sustained over the DDR protocol was significantly higher in the OW group compared to the NO group. There was no significant difference in the average energy cost of movement when VO2 was normalized to fat-free mass (OW: 17.7 +/- 5.1 vs. NO: 17.3 +/- 3.9 mL . kgFFM (-1) . min (-1)). Both groups were above the minimal ACSM recommended heart rate intensity for developing and maintaining cardiorespiratory fitness when participating in the DDR protocol (OW: 64.83 % +/- 7.14 vs. NO: 64.51 % +/- 7.71), VO2 reserve, however, did not meet ACSM standards for developing and maintaining cardiorespiratory fitness.

The Effectiveness of Dance Interventions on Physical Health Outcomes Compared to Other Forms of Physical Activity: A Systematic Review and Meta-Analysis

BACKGROUND

Physical inactivity is one of the key global health challenges as it is associated with adverse effects related to ageing, weight control, physical function, longevity, and quality of life. Dancing is a form of physical activity associated with health benefits across the lifespan, even at amateur levels of participation. However, it is unclear whether dance interventions are equally as effective as other forms of physical activity.

OBJECTIVE

The aim was to systematically review the literature on the effectiveness of structured dance interventions, in comparison to structured exercise programmes, on physical health outcome measures.

METHODS

Seven databases were searched from earliest records to 4 August 2017. Studies investigating dance interventions lasting > 4 weeks that included physical health outcomes and had a structured exercise comparison group were included in the study. Screening and data extraction were performed by two reviewers, with all disagreements resolved by the primary author. Where appropriate, meta-analysis was performed or an effect size estimate generated.

RESULTS

Of 11,434 studies identified, 28 (total sample size 1276 participants) met the inclusion criteria. A variety of dance genres and structured exercise interventions were compared. Meta-analyses showed dance interventions significantly improved body composition, blood biomarkers, and musculoskeletal function. The effect of either intervention on cardiovascular function and self-perceived mobility was equivalent.

CONCLUSION

Undertaking structured dance of any genre is equally and occasionally more effective than other types of structured exercise for improving a range of health outcome measures. Health practitioners can recommend structured dance as a safe and effective exercise alternative.

Comparison of standing balance between female collegiate dancers and soccer players

STUDY DESIGN

This study was designed as a comparison study of two cohorts.

OBJECTIVES

The hypothesis of this study was that soccer players and dancers have different balance abilities and that these differences could be objectively measured using center of pressure measurements.

BACKGROUND

Center of pressure (COP) measurements are reproducible and have been validated in the literature for assessing standing balance. The literature does not provide sensitive enough techniques for discriminating between two groups of athletes with excellent standing balance.

METHODS AND MEASURES

A Matscan pressure mat (Tekscan, Boston, MA) was used to compare COP change variability between 32 female collegiate soccer players and 32 dancers. COP was used to calculate sway index, center acquisition time, sway path length and sway velocity as measures of standing balance.

RESULTS

The dancers had significantly better balance scores (p<0.05) in 5 of 20 balance tests. Results for the remaining 15 balance tests were not significantly different.

CONCLUSION

These data show that standing balance characteristics of dancers and soccer players can be objectively measured using COP data. Dancers have certain standing balance abilities that are better than those of soccer players. The COP measurements in this study can be used as a tool in future studies investigating standing balance in different groups of athletes.

Proprioception in classical ballet dancers. A prospective study of the influence of an ankle sprain on proprioception in the ankle joint

We studied prospectively the influence of ankle sprains on proprioception as measured by recording the postural sway of classical ballet dancers. Excellent balance and coordination are important for classical ballet dancers, and postural stability requires adequate proprioception from the ankle joint. Fifty-three professional dancers from the Royal Swedish Ballet, Stockholm, and 23 nonathletes, the control group, participated in the investigation. Postural sway was recorded and analyzed with a stabilimeter using a specially designed, portable, computer-assisted force plate. Six dancers sustained ankle sprains during followup. The recordings were obtained of these dancers before and after the injuries. The stabilometry results differed among the male and female dancers and the control group as follows: 1) the male dancers demonstrated a smaller total area of sway, and 2) both the male and female dancers had a smaller mean sway on the left foot than on the right (no mean difference in sway was found between the left and right foot in the control group). In comparison with the condition before injury and with the uninjured foot, the postural stability of the dancer was impaired for several weeks after the ankle sprain. Postural stability gradually improved during rehabilitation and improvement still occurred several weeks after professional dancing had resumed.

Postural control of ballet dancers: a specific use of visual input for artistic purposes

Dance is a specific expression of human motor behaviour. This artistic physical activity depends upon an effective technical training with important postural components and necessitates the codification of sensory inputs to build mental representations of the action to be produced. Proprioception and vision being two fundamental sensory modalities in classical ballet, this study attempted to determine the importance of the visual input for postural control during the practice of this activity. First, this work compared the performances of 18 professional ballet dancers and 46 non-dancers on a platform of forces during static posturographic tests in open or closed eyes situation. Then, we studied how professional dancers achieve balance in postures specific of classical ballet: on demi-pointe and on pointe. The results indicate that visual inputs are important in classical ballet since dancers only performed better than controls in eyes open conditions. The similar results obtained on pointe with eyes open or closed conversely suggest that training in classical ballet develops specific modalities of balance which are not transferable to posture control in daily life situations.