Dancer perceptions of varied dance surfaces quantified by ...
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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