Effect of teaching with or without mirror on balance in young female ballet students

Effects of training protocols on dancers' balance: A systematic review

BACKGROUND

Balance is an essential skill for dancers, it helps reduce the risk of injury, and is related to quality of performance. This systematic review aims to investigate the effects of training protocols on the balance of dancers when compared to control groups.

METHODS

Interventional studies, published until January 2023, assessing balance in all levels of ballet, modern, and contemporary dancers were identified in the PubMed, Cochrane, Lilacs, Scielo, Embase, and SPORTDiscus databases. Publications in English, Spanish and Portuguese were considered. In two selection phases, using a standard protocol, two reviewers independently selected and extracted the data. The Downs & Black checklist was used to assess risk of bias.

RESULTS

Of the nine intervention studies included, most were classified as either "fair" or "poor" quality. Three-hundred and seventy-two dancers aged 9.6 ± 0.5 to 25.7 ± 3.7 years were analysed. The majority was female (94%), with the years of experience of ballet (35%) or ballet and modern (49%) training ranging from 4.6 ± 1.4 to 12.0 ± 7.5 years. Numerous training protocols of varying durations were found. However, neuromuscular training proved the most effective at improving balance.

CONCLUSION

Most of the studies are classified poor quality. Future studies should consider interventions lasting at least four weeks, two to three times a week, sessions between 30 and 60 min. More high-quality studies, randomized control trials using validated balance tests, as well as new validation studies for dance-specific balance tests are needed.

Does Viewing Mirror-Reflected Body Image Affect Static and Dynamic Standing Balance?

In the present study, we examined the immediate effect of allowing healthy participants to view their mirror-reflected body image on static and dynamic balance. We placed a mirror to allow participants to frontally view their own body image while maintaining a quiet stance or while engaged in a dynamic postural standing task. On measures of body sway during quiet stance, there were no effects of this visual feedback, supporting the view that human beings have no central mechanism for viewing the mirror-reflected body image to control body sway during quiet stance. However, the body deviated forward during quiet stance while viewing the mirror-reflected body image, indicating that viewing the mirror-reflected body image contributed to the anterior-posterior positioning of the body, as mediated by an ankle control strategy. For the dynamic standing task, viewing the body image induced unstable peaks of rhythmic lateral shifting of the body weight over the feet. This indicates that viewing the body image caused unstable motor commands for rhythmic lateral weight shifting. When participants made a transition from a bipedal to a unipedal stance in response to a cue, viewing the body image shortened the onset latency of the body sway. Accordingly, viewing the body image seemed to accelerate the motor execution involved in lateral weight shifting, possibly due to predictive activation of the motor system before movement onset. Considered collectively, we found static and dynamic stance balance to be influenced by viewing one's mirror-reflected body image. Viewing the mirror-reflected body image may be a means of changing static and dynamic balance in patients with impaired postural control.

Effects of Mirror and Metronome Use on Spontaneous Dance Movements

This study investigated effects of mirror and metronome use on spontaneous upper body movements by 10 preprofessional dancers in a motor task in which maximally diverse upper body movement patterns were targeted. Hand and trunk accelerations were digitally recorded utilizing accelerometers and analyzed using polar frequency distributions of the realized acceleration directions and sample entropy of the acceleration time. Acceleration directions were more variably used by the arms than by the torso, particularly so when participants monitored their performance via a mirror. Metronome use hardly affected the predictability of the acceleration time series. The findings underscore the intrinsic limitations that people experience when being asked to move randomly and reveal moderate effects of visual and acoustic constraints on doing so in dance.

Effect of Visual Condition on Performance of Balance-Related Tasks in Elite Dance Students

The purpose of this study was to investigate the effects of visual condition (low light, full light, and full light with mirror) on balance control and technical form during two technical dance movements in a group of elite collegiate dance students. Dancers demonstrated higher center of pressure velocity indicating lower control while performing a static dance task (parallel relevé retiré) and a dynamic dance task (fondu relevé en croix) under low light conditions than either lighted condition. Measures of Western ballet technique (pelvic obliquity, knee extension, and ankle plantar flexion) showed no decrement under low light conditions. No effect of concurrent mirror feedback was found on either center of pressure velocity or technical requirements of the dance tasks.

The Effectiveness of Classical Ballet Training on Health-Related Outcomes: A Systematic Review

BACKGROUND

Regular physical activity is of paramount importance to reduce chronic disease risk. Classical ballet training requires balance, strength, and range of motion. Participation in social ballet classes is increasing. Ballet training interventions may be an alternative method of regular, enjoyable activity. This review aimed to determine the effectiveness of classical ballet training interventions on physical and psychological health.

METHODS

Ten databases were searched until April 2019. The included studies investigated classical ballet training interventions of a ≥4-week duration, on any population (no restrictions on experience and clinical condition), measuring physical health or psychological outcomes.

RESULTS

Twenty-three studies (25 intervention groups) were included, comprising experienced (19 groups) and novice dancers (6 groups). In experienced populations, muscular strength was the most commonly reported outcome. However, only 25% of these studies reported improvements. With novice dancers, including clinical populations, balance showed the most positive change, improving in 75% of studies that reported this measure.

CONCLUSIONS

Classical ballet training may improve balance in novices and maintain physical activity across the life span. Experienced dancers showed no further improvement, perhaps due to an already greater ability. There was large heterogeneity between the included studies. A greater focus on classical ballet interventions for inexperienced populations is required.

Influence of foot position and vision on dynamic postural strategies during the "grand plié" ballet movement (squatting) in young and adult ballet dancers

PURPOSE

To analyse dynamic postural strategies during the "grand plié" in two different foot positions (parallel or turned out), with and without vision, and as a function of age in ballet dancers.

METHOD

Twenty young dancers (YD) aged from 8 to 16 years, and 20 adult dancers (AD) aged from 17 to 30 years were recruited. Center of pressure (CoP) and ground reaction forces (GRF) were recorded (500 Hz) during the grand plié (lowering, squatting and rising). This movement was tested with the feet parallel and with both lower limbs turned out (foot angle >140°), with eyes open (EO) and eyes closed (EC). Groups were compared using Student t-tests. Repeated analysis of variance was used to examine the effects of eyes and foot conditions, with a significance level of p < 0.05.

RESULTS

The results of this study showed that dynamic postural strategies during the "grand plié" ballet movement are influenced by age, foot position and visual condition. CoP displacement length (p < 0.003) and CoP speed (p < 0.003) were higher in YD compared with AD. CoP surface (p < 0.05), mediolateral CoP speed (p < 0.048) and GRF parameters, particularly the mediolateral (p < 0.049), were higher than in the parallel than the turned out position. In both groups all CoP (p < 0.042) and GRF parameters (p < 0.049), except the vertical component, were higher with EC than EO.

CONCLUSION

The effect of foot position was greatest with EO. The parallel position was less stable. The YD were more unstable in the parallel position, particularly with EC. For both groups, the lack of vision increased instability. These results show the importance of integrating balance training in a variety of foot positions and visual conditions, particularly during the initial stages of training to prevent injury.

Factors Dancers Associate with their Body Dissatisfaction

Body dissatisfaction constitutes an important factor in the development of eating pathologies, particularly among dancers. The aim of this research was to test the factors that dancers identified as relevant to their body dissatisfaction using an exploratory mixed method design. Participants were 369 dancers from two Spanish dance conservatories. Questionnaires assessed body dissatisfaction, abnormal eating attitudes and behaviors, and risk factors to eating disorders in the dance domain. Nine factors were found; the "teacher", the "uniform", and the "mirrors" were the most common. Individuals with a greater likelihood of developing an eating disorder identified teacherś influence as a key factor in their body dissatisfaction. Specifically, ballet dancers were more likely to indicate that teachers were a negative influence compared to students in other dance genres (contemporary, flamenco, and Spanish dance). Programs to reduce negative body image and improve positive body image in dance conservatories are needed, specifically focusing on teachers.

Does motor expertise facilitate amplitude differentiation of lower limb-movements in an asymmetrical bipedal coordination task?

The motor system's natural tendency is to move the limbs over equal amplitudes, for example in walking. However, in many situations in which people must perform complex movements, a certain degree of amplitude differentiation of the limbs is required. Visual and haptic feedback have recently been shown to facilitate such independence of limb movements. However, it is unknown whether motor expertise moderates the extent to which individuals are able to differentiate the amplitudes of their limb-movements while being supported with visual and haptic feedback. To answer this question 14 pre-professional dancers were compared to 14 non-dancers on simultaneously generating a small displacement with one foot, and a larger one with the other foot, in four different feedback conditions. In two conditions, haptic guidance was offered, either in a passive or active mode. In the other two conditions, veridical and enhanced visual feedback were provided. Surprisingly, no group differences were found regarding the degree to which the visual or haptic feedback assisted the generation of the different target amplitudes of the feet (mean amplitude difference between the feet). The correlation between the displacements of the feet and the standard deviation of the continuous relative phase between the feet, reflecting the degree of independence of the feet movements, also failed to show between-group differences. Sample entropy measures, indicating the predictability of the foot movements, did show a group difference. In the haptically-assisted conditions, the dancers demonstrated more predictable coordination patterns than the non-dancers as reflected by lower sample entropy values whereas the reverse was true in the visual-feedback conditions. The results demonstrate that motor expertise does not moderate the extent to which haptic tracking facilitates the differentiation of the amplitudes of the lower limb movements in an asymmetrical bipedal coordination task.

The Effects of Either a Mirror, Internal or External Focus Instructions on Single and Multi-Joint Tasks

Training in front of mirrors is common, yet little is known about how the use of mirrors effects muscle force production. Accordingly, we investigated how performing in front of a mirror influences performance in single and multi-joint tasks, and compared the mirror condition to the established performance effects of internal focus (IF) and external focus (EF) instructions in a two part experiment. In the single-joint experiment 28 resistance-trained participants (14 males and 14 females) completed two elbow flexion maximal voluntary isometric contractions under four conditions: mirror, IF, EF and neutral instructions. During these trials, surface EMG activity of the biceps and triceps were recorded. In the multi-joint experiment the same participants performed counter-movement jumps on a force plate under the same four conditions. Single-joint experiment: EF led to greater normalized force production compared to all conditions (P≤0.02, effect-size range [ES] = 0.46–1.31). No differences were observed between neutral and mirror conditions (P = 0.15, ES = 0.15), but both were greater than IF (P<0.01, ES = 0.79–1.84). Surface EMG activity was comparable across conditions (P≥0.1, ES = 0.10–0.21). Multi-joint experiment: Despite no statistical difference (P = 0.10), a moderate effect size was observed for jump height whereby EF was greater than IF (ES = 0.51). No differences were observed between neutral and mirror conditions (ES = 0.01), but both were greater than IF (ES = 0.20–22). The mirror condition led to superior performance compared to IF, inferior performance compared to EF, and was equal to a neutral condition in both tasks. These results provide novel and practical evidence concerning mirror training during resistance type training.

Effects of a Fragmented View of One's Partner on Interpersonal Coordination in Dance

In this study we investigated the effects of a mirror-mediated, partial view of one’s dance partner on interpersonal coordination in dance duets. Fourteen participant pairs (dyads) were asked to perform a reflectionally-symmetric eight-segment dance-relevant arm movement sequence in two visual conditions: with one dancer facing the mirror and providing a partial view on the dance partner, or both dancers facing back to back with, for both dancers, no view on one’s partner. During an eight-count beat-preparation phase, the task was paced via a metronome at three TEMPI; 1.6, 1.9, and 2.3 Hz, which was subsequently removed after which the movement sequence continued in silence. Interpersonal coordination was assessed using two tri-axial wireless accelerometers, one fixed to each dancer, that allowed the off-line kinematic analyses of dyad correlation, mean relative phase and mean standard deviation of relative phase of the up–down movements of (one of) the hands of the two dancers. In addition, two independent raters estimated the realized movement frequencies and percentage of the trial duration that the dancers moved in sync. Repeated measure ANOVAs revealed systematic effects of tempo on the performance measures, a positive effect of the use of the mirror on the coordination of the dancers’ movements but no facilitating effect of the mirror on the dancers’ synchronization. Overall, the results support the contention that when dancing to an internalized rhythmic beat the use of a mirror provides an ecological means to stabilize interpersonal coordination in dance duets without an effect on synchronization.