Dancer perceptions of varied dance surfacesquantified by the Advanced Artificial Athlete

Mr Luke Hopper B.Sc(Hons)

Dr Jacqueline Alderson PhD

Prof Bruce Elliott PhD

Prof Tim Ackland PhD

Dr Paul Fleming PhD1

1

Ballet History

Origins 17th century French courts, Louis XIV

Popularized in Western Europe 19th century

Famous international institutions

Estimated dance participation in the USA76 000 professional dancers11 000 000 student dancers(Bronner & Worthen, 1999)

Dance participation in the UKSchool children; 2nd most popular physical activity after football~4.8 million adult participants(www.danceuk.org)

Dance Science

Scientific investigation of dancer physical capacities and training principles

Medical Reports

Musculoskeletal injuries in theatrical dancers: site, frequency, and severity(Washington, 1978)

Epidemiology

Dancers can spend over 40 hours per week training(Inge et al., 1993; Nilsson et al., 2001)

High incidence of overuse injury to the lower limb similar to professionalathletes(Byhring & Bo, 2002; Nilsson et al., 2001; Solomon et al., 1995)

The mechanical properties of the dance floor surface have been suggestedto pose an injury risk(Bowling, 1989; Khan et al., 1995; Liederbach & Richardson, 2007)

Retrospective questionnaire; 19% dancers suggested floor influenced injury(Bowling, 1989)

Dance FloorsDancers suggested to; have an inherent sense of floor mechanical properties

(Washington, 1978)

require different surface properties to elite sports(Seals, 1983)

Human Surface Interactions

Human landing mechanics differ between known, unexpected or unknown surfaces(Moritz et al., 2004)

Highly adaptable to a known change in surface structure(Ferris et al., 1999)

Sport Surface Epidemiology

Confounding environmental variables & validity of surface quantification protocols(Shorten, 2007; Nigg & Segesser, 1988; Ekstrand et al., 2003; Nigg, 2003)

Dancers perform in a closed and controlled environment for large volumes of time(Inge et al., 1993; Nilsson et al., 2001)

Benefits of investigation of dancers fordance epidemiology and STARSS

Research DesignAims

1. Assess ability of dancers to perceive differences in properties of a range of dance floors

2. Assess which perceptions of AAA mechanical variable(s) best predict dancer overall ratings

3. Compare dancer perceptions with outputs of AAA mechanical test results

Cohort

Professional dancers (Royal Ballet, UK) (n=27)

Student dancers (WA Academy of Performing Arts, AUS) (n=27)

Significantly different (p<0.02) for age and experience

Floors

5x Modified samples of Harlequin liberty sprung floors

(1.2 m x 1.2 m)

18 mm 13 ply birch panels

High and low density neoprene pads

Quantified by Advanced Artificial Athlete (AAA)

Advanced Artificial Athlete(Metaalmaatwerk, NL)

9600Hz Uni-axial accelerometer

20kg Drop Mass

2200N/mm Spring

55mm Drop height

100mm Diameter Test Foot

92Hz Low Pass Butterworth

Temperature 18-21°C

Force Reduction (FR)

= (1 - Peak Surface / Peak Concrete) • 100

Energy Return (ER)

= Rebound velocity / Impact velocity

Vertical Deformation (VD)

= Peak deformation during impact – spring compression

(BSEN 14808)

-50

0

50

100

150

200

250

300

350

0.2

30

0.2

35

0.2

40

0.2

45

0.2

50

0.2

55

0.2

60

0.2

65

Ac

ce

lera

tio

n(m

s-2

)

Time (sec)

Concrete

Surface

ForceReduction

(%)

Surface Testing Results

Provided a range of FR floors

Inter day reliable

Intra floor consistent

Central 600 mm x 600 mm

Samples above and below BSEN14904 (Surfaces for sports areas:Indoor surfaces for multi-sports use)

Larger variability in ER and VD

* Indicates samples NOTsignificantly different (p>0.02)

20.37 56.66 68.19 75.41 79.890

10

20

30

40

50

60

70

80

90

100

Forc

ere

duction

(%)

70.92 41.05 49.72 45.84 38.550

10

20

30

40

50

60

70

80

90

100

Energ

yre

turn

(%)

*

-1.07

0.60 1.52 2.25 2.01

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

Vert

icald

efo

rmation

(mm

)

Floor

1 2 3 4 5

* *

BSEN 14904

Perception Testing

Questionnaire

Likhert scales FR, ER & VD

Also overall rating (OR)

Dance specific terms

Representative animation

Floors randomised

ResultsAim 1

Assess ability of dancers to perceive differences inproperties of a range of dance floors.

* Indicates perceptions NOT significantly different(p>0.02)

Dancers demonstrated;

-ability to understand the underlying concepts

-perceive differences in the mechanicalproperties

-reference to the quantification outputs of theAAA

VD floor 5 only significant difference for experience(p<0.02)

0

2

4

6

8

10

1 2 3 4 5

Vert

icald

efo

rmation

Student perceptions Professional perceptions

0

2

4

6

8

10

Energ

yre

stitu

tion

0

2

4

6

8

10

Forc

ere

duction

*

*

*

Results

Aim 2

Assess which perceptions of AAA mechanical variable(s) best predict dancer overall ratings

A combination of the perceptions were required for strongest model

Predictive ability stronger in students

Suggests more variability in professionals or other perceptual predictors

Overall Rating Linear Regression FR ER VD

Professionals r2=0.470 F=40.66 ß=0.500 ß=0.597 ß=-0.438

Students r2=0.747 F=132.76 ß=0.629 ß=0.546 ß=-0.305

ResultsAim 3

Compare dancer perceptions with outputs of surface standards BSEN 14808 and 14904

0

2

4

6

8

10

1 2 3 4 5Student perceptions Professional perceptions

0

2

4

6

8

100

2

4

6

8

10

20.37 56.66 68.19 75.41 79.890

20

40

60

80

100

Forc

ere

ductio

n(%

)

70.92 41.05 49.72 45.84 38.550

20

40

60

80

100

Energ

yre

turn

(%)

-1.07

0.60 1.52 2.25 2.01

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

Vert

icaldefo

rmatio

n(m

m)

Floor1 2 3 4 5

Relative difference between floors 4 & 5

Inverse relationship

High AAA variability

1 2 3 4 5 1 2 3 4 5

Same rank order

Conclusions

Dancers demonstrated ability to perceive changes in floor properties

Perceptions generally not dependent on experience

BUT

Dance experience may increase preference complexity

AAA measures appear to partially represent dancer perceptions

Neither perceptions or AAA validated gold standardMore investigation required

Further Work

Hopper, L., Allen, N., Wyon, M., Alderson, J., Elliott, B., & Ackland, T. R.

(2009). Ballet dancer injuries rates during rehearsal and

performance on varied dance surfaces. Paper presented at the

27th International conference on biomechanics in sports, Limerick,

Ireland.

PhD Research

Ankle joint mechanics during dancer landings on varied surfaces

Movement variability during dancer landings on varies surfaces

Follow-up research

Dancer perceptions; larger floor samples, open questions

Acknowledgements