The Effect of 16 Weeks of Lower-Limb Strength Training in Jumping Performance of Ballet Dancers

Abstract

Jumping ability is considered a determinant of performance success. It is identified as one of the predictors and talent identification in many sports and dance. This study aimed to investigate the effect of 16 weeks of lower-limb strength training on the jumping performance of ballet dancers. A total of 24 participants from the same dance school were randomly selected in the control group [CG; n = 10; aged 13.00 (1.49) years; 43.09 (9.48) kg and 1.53 (0.11) m] and the intervention group [IG; n = 14; aged 12.43 (1.45) years; 38.21 (4.38) kg and 1.51 (0.07) m], evaluated before and after the applied strength training program mainly using the body weight of each participant. Jump performance was assessed using MyJump2, a scientifically validated mobile phone app. Intergroup and intragroup comparisons were assessed, and the magnitude of change was calculated using the effect size (ES). While CG significantly decreased the relative power over time (p < 0.001, ES = −0.29: small), results from the intragroup comparisons suggest that IG significantly increased the countermovement jump (CMJ) height (p < 0.001, ES = 1.21: large), the relative force (p < 0.001, ES = 0.86: moderate), maximal velocity (p < 0.001, ES = 1.15: moderate), and relative power (p < 0.001, ES = 1.37: large). We concluded that a 16-week strength training program of lower limbs is an effective way to improve CMJ height in young dancers. Supplementary strength training appears to be the determinant for the improvement of the jumping performance of ballet dancers.

Full text

fphys-12-774327 January 6, 2022 Time: 14:4 # 1
ORIGINAL RESEARCH
published: 12 January 2022
doi: 10.3389/fphys.2021.774327
Edited by:
Henrique Pereira Neiva,
University of Beira Interior, Portugal
Reviewed by:
José Vilaça Alves,
University of Trás-os-Montes and Alto
Douro, Portugal
Ana Ruivo Alves,
University of Beira Interior, Portugal
*Correspondence:
Lurdes Ávila-Carvalho
lurdesavila2@gmail.com
Specialty section:
This article was submitted to
Exercise Physiology,
a section of the journal
Frontiers in Physiology
Received: 11 September 2021
Accepted: 13 December 2021
Published: 12 January 2022
Citation:
Ávila-Carvalho L, Conceição F,
Escobar-Álvarez JA, Gondra B, Leite I
and Rama L (2022) The Effect of 16
Weeks of Lower-Limb Strength
Training in Jumping Performance
of Ballet Dancers.
Front. Physiol. 12:774327.
doi: 10.3389/fphys.2021.774327
The Effect of 16 Weeks of
Lower-Limb Strength Training in
Jumping Performance of Ballet
Dancers
Lurdes Ávila-Carvalho1,2*, Filipe Conceição2,3 , Juan A. Escobar-Álvarez2,4,
Beatriz Gondra2, Isaura Leite2and Luís Rama1,5
1Faculty of Sports Science and Physical Education, University of Coimbra, Coimbra, Portugal, 2Faculty of Sport, Center of
Research, Education, Innovation and Intervention in Sport (CIFI2D), University of Porto, Porto, Portugal, 3LABIOMEP, Porto
Biomechanics Laboratory, University of Porto, Porto, Portugal, 4School of Health and Life Sciences, University of the West
of Scotland, Ayr, United Kingdom, 5Research Center for Sport and Physical Activity (CIDAF), Faculty of Sports Science and
Physical Education, University of Coimbra, Coimbra, Portugal
Jumping ability is considered a determinant of performance success. It is identified as
one of the predictors and talent identification in many sports and dance. This study
aimed to investigate the effect of 16 weeks of lower-limb strength training on the jumping
performance of ballet dancers. A total of 24 participants from the same dance school
were randomly selected in the control group [CG; n=10; aged 13.00 (1.49) years;
43.09 (9.48) kg and 1.53 (0.11) m] and the intervention group [IG; n=14; aged 12.43
(1.45) years; 38.21 (4.38) kg and 1.51 (0.07) m], evaluated before and after the applied
strength training program mainly using the body weight of each participant. Jump
performance was assessed using MyJump2, a scientifically validated mobile phone
app. Intergroup and intragroup comparisons were assessed, and the magnitude of
change was calculated using the effect size (ES). While CG significantly decreased the
relative power over time (p<0.001, ES = −0.29: small), results from the intragroup
comparisons suggest that IG significantly increased the countermovement jump (CMJ)
height (p<0.001, ES =1.21: large), the relative force (p<0.001, ES =0.86: moderate),
maximal velocity (p<0.001, ES =1.15: moderate), and relative power (p<0.001,
ES =1.37: large). We concluded that a 16-week strength training program of lower
limbs is an effective way to improve CMJ height in young dancers. Supplementary
strength training appears to be the determinant for the improvement of the jumping
performance of ballet dancers.
Keywords: jump, explosive, strength, power, dance
INTRODUCTION
Both sports and dance culminate in public performances. The intersections of dance and sports
are reported since some athletes and coaches use strength training to improve their performance
(Markula, 2018), particularly in aesthetic sports such as figure skating and gymnastics. In addition
to the dramatic and artistic performance of dancers, dance demands high levels of motor
performance, which include a high jumping ability (Koutedakis et al., 2005). Several authors
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Ávila-Carvalho et al. Jumping Performance of Ballet Dancers
recognize that dancers with a more developed jumping ability
also improve the perception of aesthetic and artistic components
of the choreography (Wyon et al., 2006;Angioi et al., 2009;
Rafferty, 2010). Others underline the importance of jumping
ability in talent identification in dance (Walker et al., 2010).
Studies involving dance students report that the increase
in strength is crucial for the dancers to perform well,
especially concerning the use of the lower limbs (essential in
jumping) (Fração et al., 1999). In fact, given the abundance
of ballistic actions in ballet (e.g., jumps and changes of
direction), improvements in jump height may be beneficial
for the dancers as a guide to specific training plans that
can improve either maximal force or velocity capabilities
(Alvarez et al., 2020). The countermovement jump (CMJ)
is usually used to evaluate the power output of the lower
limbs as ballistic movements that include both concentric and
eccentric phases closer to the sports and ballet movements.
In fact, the CMJ and drop jump performances are related
to grand jeté leap performance in dancers with different skill
levels, being considered useful tools for monitoring the power-
generating capacity of the lower body of the dancer, thus
giving insight into the overall jumping capacity of the dancer
(Blanco et al., 2019). Consequently, both strength and speed
development are fundamental to increasing jumping ability
(Jimenez-Reyes et al., 2014).
Some studies observed the effect of training programs to
improve jumping performance, either in dancers or in rhythmic
gymnastics, which is the gymnastics discipline more equivalent
to dance (Wang et al., 2010;Piazza et al., 2014;Komeroski
et al., 2016;Mlsnová and Luptáková, 2017;Tsanaka et al.,
2017;Dobrijevi´
c et al., 2018;Skopal et al., 2020;Stoši´
c et al.,
2020). Focusing on dance, previous studies have applied for
a specific strength training program, for 9 weeks, based on
and adjusted according to the force-velocity profile of each
dancer (Escobar-Alvarez et al., 2019); evaluated whether a 9-
week resistance training program could have a significant effect
on the strength and power of the lower limbs in adolescent
dancers (Dowse et al., 2020); applied, for 10 weeks, a modern
and recreational dance exercise program and trunk and leg
muscle strengthening exercises in university dance students
(Stoši´
c et al., 2020) and used their ballet classes, modified with
a focus on lower-limb strength (reduction in bar duration (from
450to 200) and the petit and grand allegro exercises at the
beginning of center work, for 8 weeks, as an intervention to
analyze jumping ability (Tsanaka et al., 2017). Regarding the
results about the jump height, four studies (Tsanaka et al., 2017;
Escobar-Alvarez et al., 2019;Dowse et al., 2020;Stoši´
c et al.,
2020) obtained positive results with significant differences, i.e.,
the applied training promoted improvements in the vertical
jump height of the dancer. Concerning the instrument, two
studies have used MyJump2 with ballet dancers, but only
one conducted an intervention (Escobar-Alvarez et al., 2019;
Alvarez et al., 2020). These findings of the authors suggest
that the experimental group presented significant differences
with large effect sizes (ESs) in CMJ height and other jumping
performance variables, namely, the theoretical maximal force
(Escobar-Alvarez et al., 2019). Additionally, measurements of
the distance covered by the center of mass during push-off
are highlighted (Samozino et al., 2008, 2012, 2014) to control the
growth process of the participants over time.
Despite the known technical and physical demands of elite
dance, traditionally, strength training has not been considered
important to the ongoing development of adolescent dancers
(Dowse et al., 2020). We found only one study that reported
an intervention program aiming to improve the jumping
performance of younger dancers using traditional external
loads (Dowse et al., 2020). Our study aimed to promote
strength training mainly using the body weight of an individual.
We hope that this will raise the awareness of the dance
teachers toward the strength training benefits to enhance
the jumping performance of the dancers. Therefore, this
study provides an example of a training program without
any equipment that could be applied in dance classes of
young ballet dancers.
This study aimed to investigate the effect of 16 weeks of lower-
limb strength training in the jumping performance of classic
ballet dancers. For this, we (1) evaluated the mechanical variables
during the CMJ of dancers, (2) proposed a specific training
program, for 16 weeks, to improve the jumping performance, and
(3) compared the mechanical variables during the CMJ of dancers
before and after a specific jump training program application. We
hypothesized that the proposed training program will positively
affect the CMJ height of the dancers.
MATERIALS AND METHODS
The following sample inclusion criteria were established:
(1) enrollment at the educational institution participating in the
study; (2) absence of injury that prevented them from training
in the last 3 months, during the intervention and at the time of
evaluation; (3) no involvement in any complementary physical
training or sports activity during the 16 weeks of intervention;
and (4) attendance at a minimum of 80% of training sessions.
Table 1 shows the sample characterization of the control group
(CG) and the intervention group (IG).
Our sample was composed of 24 ballet dancers from the same
school dance and was divided into the CG (n=10) and the
TABLE 1 | Sample characterization [Mean (SD)].
Variables CG (n=10)
mean (SD)
IG (n=14)
mean (SD)
p
Age (years) 13.00 (1.49) 12.43 (1.45) 0.357
Weight (kg) 43.09 (9.48) 38.21 (4.38) 0.156
Height (m) 1.53 (0.11) 1.51 (0.07) 0.487
BMI (kg/m2) 18.05 (2.46) 16.77 (1.02) 0.148
HPO (cm) 0.36 (0.07) 0.39 (0.07) 0.348
Years of practice 5.00 (1.83) 6.50 (3.52) 0.189
Hours/training/week 28.50 (3.37) 27.93 (5.14) 0.762
p≤0.05, independent measures t-test; pretest between groups.
CG, control group; IG, intervention group; BMI, body mass index; HPO, height of
push-off; SD, standard deviation.
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Ávila-Carvalho et al. Jumping Performance of Ballet Dancers
IG (n=14). Although the participants were selected randomly,
the groups did not have the same number of subjects because
four dancers from the CG were involved in a complementary
sports activity, which led to their exclusion from the CG sample.
The sample size was restricted to the number of higher-level
dancers from the dance school that accepted and approved to
carry out this study.
It is essential to highlight that the CG was composed
of 9 female and 1 male dancers, with an average age of
13.00 (1.49) years, 5 years of regular dance practice, and
28.50 h of training per week (Table 1). The IG was composed
of 10 female and 4 male dancers, with an average age
of 12.43 (1.45) years, 6.50 years of practice, and 27.93 h
of weekly training. No significant differences were found
between the CG and the IG for any of the variables in
Table 1.
All ethical procedures were carried out following the
Declaration of Helsinki, and the study was approved by the local
Ethical Committee (CE/FCDEF-UC/00742021). All participants
and their guardians (dancers aged under 18 years) were informed
of the benefits and risks of the research. Before the beginning
of the study, they signed an informed consent document for
testing, implementation of the training protocol, and publication
of collected data.
The variables assessed in this investigation were the weight
(kg), height (m), body mass index (BMI) (kg/m2), CMJ (cm),
relative force (N/kg), maximal velocity (m/s), relative power
(W/kg), and the height of push-off (HPO) (cm) of each dancer.
The relative values to body mass were calculated by dividing the
output of each subject by their mass as previous findings, whereas
relative force was calculated by dividing the force output of each
subject by their mass (Dowse et al., 2020).
These mechanical variables were used in our study to better
understand the CMJ high performance as stated by Cormie et al.
(2011) that force and velocity are considered as the fundamental
features of mechanical power output in sport movements.
Before the beginning of the study, the body weight (kg)
and the stature (m) were collected using a Tanita SC-330
(TANITA Corp, Tokyo, Japan) and an aluminum stadiometer
(Seca 713 model; Seca, Postfach, Germany), respectively. HPO
assessment (Samozino et al., 2008, 2012, 2014) implicates two
measurements of lower-limb length (in centimeters) by an
experienced researcher using a tape measure (SECA, 201). First,
with the participant lying down and the ankle fully extended,
the distance from the iliac crest to toes and, second, squatting
at 90◦(knee flexion) from the iliac crest to the ground were
measured. These measures were collected before each of the 3
evaluation moments to control the growth process of dancers
along the 16 weeks of training. The time-lapse between the
last training session and the evaluation moments was always
proximally 72 h. Both groups were evaluated in pretest and after
the 16 weeks of training. Since the IG experienced an unusual
training strategy, an intermediated control moment of jump
performance progression was programmed, which occurs at the
8th week only in IG.
Before all control time points, dancers performed their
habitual warm-up routine consisting of 15 min of jogging,
dynamic stretching (plantar flexors, hip extensors, hamstrings,
hip flexors, and quadriceps femoris), and preparatory CMJs, also
following previous orientations (Escobar-Alvarez et al., 2019).
Before each jump, participants were instructed to remain in
a standing position with their hands on their hips. From this
position, participants performed a CMJ as described earlier
(Jimenez-Reyes et al., 2014). A maximum effort CMJ was used to
assess lower-body explosive power and the effect of the stretch-
shorten cycle of each subject (Dowse et al., 2020). The instrument
used was MyJump2, an app of iPhone 5 specially developed to
monitor the vertical jump ability of the athlete in a valid, reliable,
and economical way in adults (Balsalobre-Fernández et al., 2015;
Jiménez-Reyes et al., 2017), and Samozino’s method was used
to monitor children (Morin and Samozino, 2016;Bogataj et al.,
2020). The analysis of jumping performance using MyJump2
evoked recently in scientific research (Samozino et al., 2012,
2014;Balsalobre-Fernández et al., 2015;Jimenez-Reyes et al.,
2016;Morin and Samozino, 2016). This method is based on
the fundamental laws of mechanics, which proposes an accurate
and reproducible field method to evaluate the power output
of lower limbs and allows a precision similar to that obtained
with specific laboratory ergometers (force platform method)
(Samozino et al., 2008). This instrument can be used to monitor
the performance of the athletes and dancers without expensive
laboratory equipment or moving the athletes and dancers from
their usual practice zone. It allows assessing the external force
developed and the maximum speed capacity related to body mass
(Jimenez-Reyes et al., 2014;Samozino et al., 2014;Jiménez-Reyes
et al., 2017), thus personalizing the results to the characteristics of
individual athletes or dancers.
Both groups (IG and CG) maintained the standardized
training regimen (as presented in Supplementary Table 1). In
addition, the IG followed a program of the lower-limb strength
training session two times a week during the 16 weeks of
intervention. Dancers performed a training program (20 min)
mainly based on exercises using their body weight, following
previous recommendations for youth training (Faigenbaum et al.,
2009). The training program had four phases: phase 1 (weeks
1–4) was composed of full squat, single-leg squat, and step-up
exercises; phase 2 (weeks 5–10) was composed of introducing
box jumps, single-leg jumps, burpees, and lunges step-ups;
phase 3 (weeks 11–13) was composed of Russian squats in
pairs, bouncing, CMJ, and lateral step-ups; and phase 4 (week
14–16) was composed of isometric squats, single-leg squat
jumps, leg press in pairs, and CMJ. Details about repetitions,
sets, recovery, and duration of each phase are presented in
Supplementary Table 2.
All data are presented as means (SDs) using IBM SPSS
Statistics for Windows, Version 27.0. Armonk, NY, United States.
The normal distribution of the study variables was assessed using
the Shapiro–Wilk test. Intergroup and intragroup comparisons
were evaluated by an independent measure and a repeated
measures t-test, respectively. We also conducted a repeated-
measures ANOVA with Bonferroni adjustment (3 evaluation
moments) to include a data collection performed at the 8th
week only at the IG as a control measure of jump performance
evolution. The level of significance was set at p≤0.05.
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Intragroup magnitudes of change were calculated with the
following S (Hopkins, 2004). The criterion for interpreting
these magnitudes was as follows: <0.2, trivial change;
0.2–0.6, small; 0.6–1.2, moderate; 1.2–2, large; >2.0,
very large (Hopkins et al., 2009). The probability that these
differences exist was assessed via magnitude-based qualitative
inferences (Batterham and Hopkins, 2006). Probabilities that
differences were higher than, lower than, or similar to the
smallest worthwhile difference were defined by the following
scale: <0.5%, almost certainly not; <5%, very unlikely; <25%,
unlikely, probably not; 25%–75%, possibly, possibly not; >75%,
likely, probably; >95%, very likely; >99.5%, almost certainly.
Finally, for the intergroup comparison, we used the ES from
Cohen’s D, using the following scale for interpretation: 0.2–0.5,
small; 0.5–0.8, moderate; >0.8, large (Cohen, 1988).
RESULTS
Although our sample is composed of female and male dancers,
similar to a previous study (Dallas et al., 2014), no significant
differences (p≥0.05) were found between the sexes in the
jumping performance. Accordingly, we considered them as one
group for the study analysis. Table 2 shows the intergroup
comparison (CG and IG) of the jumping performance variables
during the pre-post intervention.
In pretest, the CG presented significantly higher CMJ
(p=0.039, ES =0.911: large), relative force (p=0.004,
ES =1.326: large), maximal velocity (p=0.035, ES =0.931:
large), and relative power values (p=0.004, ES =1.328: large) in
comparison to the IG. In posttest, no significant differences were
found between groups in any of the study variables.
Table 3 shows the intragroup comparisons for anthropometric
and jumping performance variables.
The CG significantly decreased relative power values over
time (p<0.001). In contrast, the IG significantly increased
all variables, namely, the anthropometric measurements, weight
(p<0.001, ES =0.43: small), height (p<0.001, ES =0.19: trivial)
and BMI (p≤0.003, ES =0.51: small), CMJ (p<0.001, ES =1.21:
large), relative force (p<0.001, ES =0.86: moderate), maximal
velocity (p<0.001, ES =1.15: moderate), and relative power
(p<0.001, ES =1.37: large).
Table 4 presents the intragroup comparison in the IG dancers
during the 3 evaluation moments (initial, after 8 weeks, and after
16 weeks of training protocol).
Finally, Table 4 presents an intermediate evaluation moment,
including the IG dancers as a control measure of jump
performance evolution. It indicates that the anthropometric
variables significantly increased over time, but the height of
the dancer only differs significantly between moments 1–3 and
2–3 (p=0.002). Regarding the jumping performance, CMJ
(p<0.001), maximal velocity (p<0.001), and relative power
(p<0.001) increased significantly and progressively across all
evaluation moments. Finally, relative force increased significantly
between moments 1–2 and 1–3 (p<0.001).
DISCUSSION
This study aimed to investigate the effect of 16 weeks of
lower-limb strength training on the jumping performance of
ballet dancers. We have compared the jumping performance
variables during the CMJ of dancers before and after a
training program, for 16 weeks. Our findings confirm the
hypothesis formulated initially since the training program
positively affected the CMJ height of the dancers. While the
CG significantly decreased relative power values over time
(p<0.001), intragroup comparisons indicate that the IG
significantly increased the CMJ height (p<0.001, ES =1.21:
large), relative force (p<0.001, ES =0.86: moderate), maximal
velocity (p<0.001, ES =1.15: moderate), and relative power
(p<0.001, ES =1.37: large) after the 16-week training
program. The ES interpretation and the individual response
results suggest that these improvements in CMJ, relative force,
velocity, and relative power represent almost certainly (100%)
a positive effect from the training program (Table 3), which
supports its efficiency.
In fact, our findings suggest that in pretest, the CG presented
significantly higher CMJ (p=0.039, ES =0.911: large), relative
force (p=0.004, ES =1.326: large), maximal velocity (p=0.035,
ES =0.931: large), and relative power values (p=0.004,
ES =1.328: large) in comparison to the IG. Regarding the
CMJ, this advantage of the CG over the IG in pretest [29.33
(5.73) cm vs. 25.10 (3.70) cm, respectively] with a large ES
is in opposition with the previous findings where the IG
TABLE 2 | Intergroup comparison of jumping performance variables pre-post intervention.
Variables CG pretest (N=10)
mean (SD)
IG pretest (N=14)
mean (SD)
pES CG posttest (N=10)
mean (SD)
IG posttest (N=14)
mean (SD)
pES
Weight (kg) 43.09 (9.48) 38.21 (4.38) 0.156 0.704 43.46 (9.69) 40.21 (4.56) 0.345 0.456
Height (m) 1.53 (0.11) 1.51 (0.07) 0.487 0.293 1.54 (0.11) 1.52 (0.07) 0.657 0.187
BMI (kg/m2) 18.05 (2.46) 16.77 (1.02) 0.148 0.728 18.07 (2.42) 17.32 (1.08) 0.377 0.428
CMJ (cm) 29.33 (5.73) 25.10 (3.70) 0.039* 0.911 28.60 (6.24) 29.85 (3.43) 0.534 −0.261
Relative force (N/kg) 17.74 (0.96) 16.38 (1.07) 0.004* 1.326 17.19 (1.76) 17.36 (1.09) 0.773 −0.121
Maximal velocity (m/s) 1.20 (0.11) 1.11 (0.08) 0.035* 0.931 1.18 (0.12) 1.21 (0.07) 0.460 −0.311
Relative power (W/kg) 21.25 (2.80) 18.14 (1.96) 0.004* 1.328 20.89 (2.96) 20.99 (2.01) 0.923 −0.041
CMJ, countermovement jump; ES, effect size (Cohen, 1988). *p ≤0.05.
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TABLE 3 | Intragroup comparison of anthropometric and jumping performance variables pre-post intervention.
Variables Weight (kg) Height (m) BMI (kg/m2) CMJ (cm) Relative
force (N/kg)
Maximal
velocity (m/s)
Relative
power (W/kg)
CG (n=10) Pretest
mean (SD)
43.09 (9.48) 1.53 (0.11) 18.05 (2.46) 29.33 (5.73) 17.74 (0.96) 1.20 (0.11) 21.25 (2.80)
Posttest
mean (SD)
43.46 (9.69) 1.54 (0.11) 18.07 (2.42) 28.60 (6.24) 17.19 (1.76) 1.18 (0.12) 20.89 (2.96)
p 0.069 0.096 0.574 0.273 0.256 0.263 <0.001*
ES 0.04 (0.03) 0.04 (0.04) 0.01 (0.03) −0.12 (0.18) −0.48 (0.72) −0.14 (0.21) −0.29 (0.42)
95% CL 0, 0.07 0, 0.08 −0.02, 0.04 −0.3, 0.07 −1.2, 0.24 −0.35, 0.07 −0.71, 0.13
Inference Trivial Trivial Trivial Trivial Small Trivial Small
Individual
response
Probability Almost
certainly
Almost
certainly
Almost
certainly
Likely Possibly Possibly Possibly
Positive-trivial-
negative
0-100-0 0-100-0 0-100-0 1-78-21 6-19-75 1-69-30 3-32-65
IG (n=14) Pretest
mean (SD)
38.21 (4.38) 1.51 (0.07) 16.77 (1.02) 25.10 (3.70) 16.38 (1.07) 1.11 (0.08) 18.14 (1.96)
Posttest
mean (SD)
40.21 (4.56) 1.52 (0.07) 17.32 (1.08) 29.85 (3.43) 17.36 (1.09) 1.21 (0.07) 20.99 (2.01)
p<0.001* <0.001* 0.003* <0.001* <0.001* <0.001* <0.001*
ES 0.43 (0.13) 0.19 (0.07) 0.51 (0.24) 1.21 (0.26) 0.86
(0.22)
1.15 (0.25) 1.37 (0.3)
95% CL 0.3, 0.56 0.12, 0.26 0.27, 0.75 0.95, 1.47 0.64, 1.08 0.9, 1.4 1.07, 1.67
Inference Small Trivial Small Large Moderate Moderate Large
Individual
response
Probability Almost
certainly
Likely Almost
certainly
Almost
certainly
Almost
certainly
Almost
certainly
Almost
certainly
Positive-trivial-
negative
100-0-0 39-61-0 98-2-0 100-0-0 100-0-0 100-0-0 100-0-0
95% CL, 95% confidence limits. *p ≤0.05 (significant differences); ES – effect size (Hopkins, 2004).
presented an initial advantage in this variable (Escobar-Alvarez
et al., 2019). Besides this initial advantage (of 4.23 cm in
comparison to the IG), the intragroup comparisons indicate that
the training program allowed the IG to increase this variable
by 4.75 cm [achieving 29.85 (3.43) cm]. In contrast, the CG
jump height declined to 28.60 (6.24) cm after the 16 weeks,
despite previous findings indicating minimal changes in CG
jump height over time [e.g., 27.3 (2) cm vs. 27.5 (2) cm]
(Escobar-Alvarez et al., 2019).
Previous studies that observed the effect of training programs
in the jump height of dancers have also obtained improvements
in this variable with values pre-post diverging between 16.9 (2.9)
cm and 18.9 (2.7) cm (p<0.001, d=0.36: small ES) pre-post
30 weeks of a plyometric training program and in CMJ with arm
swing dancers jumped 21.5 (3) cm vs. 25 (2.8) cm (p<0.001,
d=1.21: large), an ES equal to our findings in CMJ (Mlsnová
and Luptáková, 2017); 22.50 (4.21) cm and 25.47 (4.95) cm pre-
post a 10-week modern and recreational dance exercise program
and trunk and leg muscle strengthening exercises (Stoši´
c et al.,
2020); 26.93 (2.78) cm and 27.35 (3.06) cm pre-post an 8-week
protocol (Tsanaka et al., 2017); and 29.3 (3.2) cm and 33.5 (3.7)
cm with a significant improvement (Escobar-Alvarez et al., 2019)
aligned with our findings. Still, in studies without interventions,
CMJ height values ranged between 23.34 (1.72) cm in dancers
aged 15 (1.07) years (Rojano-Ortega, 2020) and 28.29 (3.42)
cm in dancers aged 18.94 (1.32) years (Alvarez et al., 2020). In
comparison, in this study, the average age of IG dancers was 12.43
(1.45) years and the pre-post CMJ height ranged between 25.10
(3.70) cm and 29.85 (3.43) cm, underlining the proficiency of our
training program in the jump height of IG dancers.
Regarding the significant improvements in the IG relative
force (16.38 (1.07) N/kg vs. 17.36 (1.09) N/kg, p<0.001,
ES =0.86: moderate) and relative power (18.14 (1.96) W/kg vs.
20.99 (2.01) W/kg, p<0.001, ES =1.37: large), and since our
sample was composed of younger dancers, it was important to
calculate these variables relative to body mass of each dancer
from simple computation measures based on body mass, jump
height (from flight time), and push-off distance (Jiménez-Reyes
et al., 2017). A previous study obtained a significant improvement
in lower-body peak force after a resistance training program in
adolescent dancers (Dowse et al., 2020). We observed that our
relative power values are lower than those observed in other
studies with older dancers, such as 27.14 (1.80) W/kg (Rojano-
Ortega, 2020) and values pre-post an intervention in rhythmic
gymnastics ranging from 21.66 (4.09) W/kg to 23.98 (4.48) W/kg
with a 9.67% improvement according to the authors (Grande
Rodríguez et al., 2010). Although we also obtained significant
improvements in the IG maximal velocity [1.11 (0.08) m/s vs.
1.21 (0.07) m/s, p<0.001, ES =1.15: moderate], previous studies
have also obtained higher values, such as 2.30 (0.12) m/s vs. 2.31
(0.13) m/s in dancers (Tsanaka et al., 2017) and 2.33 (0.18) m/s
vs. 2.45 (0.23) m/s in rhythmic gymnastics (Grande Rodríguez
et al., 2010). Previous findings suggest that dance training
mainly develops velocity capabilities, and supplemental force
training may be beneficial regarding the high number of dramatic
elevations that dance performance requires (Alvarez et al., 2020).
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Ávila-Carvalho et al. Jumping Performance of Ballet Dancers
TABLE 4 | Intervention group, intragroup comparison (3 evaluation moments).
Variables N Pretest
mean (SD)
Posttest
mean (SD)
Posttest2
mean (SD)
p
(Wilks Lambda)
Post hoc
(Bonferroni)
Weight (kg) 14 38.21 (4.38) 38.78 (4.34) 40.21 (4.56) <0.001* All moments
Height (m) 14 1.51 (0.07) 1.51 (0.07) 1.52 (0.07) 0.002* Moments 1–3, 2–3
BMI (kg/m2) 14 16.77 (1.02) 16.95 (1.05) 17.32 (1.08) 0.010* All moments
CMJ (cm) 14 25.10 (3.70) 28.03 (3.82) 29.85 (3.43) <0.001* All moments
Relative force (N/kg) 14 16.38 (1.07) 17.01 (0.98) 17.36 (1.09) <0.001* Moments 1–2, 1–3
Maximal velocity (m/s) 14 1.11 (0.08) 1.17 (0.08) 1.21 (0.07) <0.001* All moments
Relative power (W/kg) 14 18.14 (1.96) 19.92 (2.06) 20.99 (2.01) <0.001* All moments
*p ≤0.05.
As stated previously, we controlled the growth of the dancers
over the 16 weeks of training using HPO measurements. Still,
younger dancers are inevitably in maturation and growing
processes, similar to previous studies (Dowse et al., 2020),
which may be a possible justification for these dissimilarities.
Additionally, female and male dancers did not differ significantly
in the jumping performance variables (p≥0.05). The apparent
sample homogeneity could be explained by the maturation
process, whereas girls could be at a higher maturity stage
and balanced the performance of the boys. Accordingly, we
considered them as one group for the study analysis.
Since we could not measure the jumping performance every
3 weeks during the program, and 1 week after the end of
the program as recommended (Jiménez-Reyes et al., 2019),
the additional evaluation moment at week 8, precisely in the
middle of the protocol, represented a control measure of the
IG jump performance evolution. After 8 weeks of avoiding
external load and promoting working with the bodyweight of an
individual as much as possible following the recommendations
for youth training Faigenbaum et al. (2009), the training
program included exercises where dancers had to overcome
the strength of a partner to perform specific exercises (e.g., leg
press with the partner sitting on their feet, see Supplementary
Material). This adjustment to the training program reveals that
an external resistance may be an essential aid in improving
the jumping performance of dancers (Escobar-Alvarez et al.,
2019). Additionally, it discloses the importance of controlling
the training and adapting it to the individual needs of the
athlete (Alvarez et al., 2020), that is, of including intermediate
evaluation moments within the training program applications
in scientific research; considering both training content and
training duration together may enable more individualized,
specific, and effective training monitoring and periodization
(Jiménez-Reyes et al., 2019).
The training program of this study included exercises that
develop the strength component, exercises that stimulated the
explosive strength, and ballistic exercises that correspond to the
stretch-shortening cycle action (Escobar-Alvarez et al., 2019).
Although not significant, the CG CMJ height, relative force,
and maximal velocity values decreased and the relative power
decreased significantly (p<0.001, ES = − 0.29: small) during
the 16 weeks with standard ballet classes. These findings clearly
correspond to previous research suggesting that dance training
alone may not provide sufficient overload to evoke a physiological
change in adolescent dancers and identified that the inclusion
of a strength training program facilitated improvements in
maximum lower-body strength (Koutedakis et al., 2007) and
vertical CMJ height (Brown et al., 2007). While the literature
provides contradictory results regarding the determination of the
optimal plyometric volume to enhance jumping performance,
two previous studies suggest that a low volume in plyometric
jumps can lead to a higher increase in CMJ (Chen et al., 2013;
Baena-Raya et al., 2019). In contrast, a previous meta-analysis
stated that training protocols based on jumps (plyometric) or
resisted training weightlifting exercises provide similar results in
jumping performance (Berton et al., 2018).
In fact, the significant and progressive increment over all of
the evaluation moments of the CMJ (p<0.001) is aligned with
previous outcomes that also conducted additional evaluation
moments (Escobar-Alvarez et al., 2019), suggesting that these
protocols are an effective way to improve CMJ height in female
ballet dancers. This is a significant step forward for the dance
conditioning literature and provides a platform for research and
practice in dance-specific additional training (Véliz et al., 2016).
Other studies also showed significant improvements in the
jumping performance of dancers (Wang et al., 2010;Komeroski
et al., 2016;Tsanaka et al., 2017;Escobar-Alvarez et al., 2019;
Stoši´
c et al., 2020) and rhythmic gymnasts (Piazza et al.,
2014;Dobrijevi´
c et al., 2018;Dallas et al., 2020) as a result
of training interventions, and the improvements in jumping
performance are consistent with previous findings in ballet
dancers (Escobar-Alvarez et al., 2019;Alvarez et al., 2020) and
in other sports disciplines (Jimenez-Reyes et al., 2016,Jiménez-
Reyes et al., 2019). We suggest an exercise prescription based on
the individual needs and the physical demands of ballet, jazz, and
contemporary dancers as referred to in previous studies (Alvarez
et al., 2020;Dowse et al., 2020).
Our results are aligned with previous findings, suggesting
that incorporating resistance training may enhance strength and
power adaptations in adolescent dancers, which can be achieved
with minimal equipment and can be performed in the training
space of the dancers, as our previous design of the training
programs indicates (Dowse et al., 2020;Skopal et al., 2020). Our
findings support earlier recommendations regarding integrating
resistance training methods (Véliz et al., 2016;Tsanaka et al.,
2017) or strength and conditioning coaches (Tsanaka et al., 2017)
to deliver systematic resistance training to adolescent dancers.
Other authors also refer that this may facilitate skill acquisition
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Ávila-Carvalho et al. Jumping Performance of Ballet Dancers
during growth and reduce the potential for injury (Brown
et al., 2007) and that the inclusion of strength training may be
able to manage growth and maturational-related changes that
commonly lead to decrements in strength, balance, and the ability
to master dance-specific technical skills (Daniels et al., 2001).
Furthermore, by demonstrating the potential for adaptation
within an adolescent cohort, it is hoped that this will increase
the awareness of the strength training benefits and encourage
dancers and support staff to consider a more integrated approach
to training (Dowse et al., 2020).
We recognize that our study presents some limitations, such
as a reduced sample size in IG and CG, including only ballet
dancers. It is not known whether the results are generalizable
to other dance styles. We also acknowledge that our sample was
formed by younger dancers who were in the maturation process.
Although we did not control the maturity of the participants,
the growth process was perceived by the HPO measure, since
it would have a direct influence on the validity and reliability
of the instrument used. This marker did not show a significant
modification along the intervention period, which led the authors
to assume maturity stability during the study. We also included
female and male participants, which can influence the results.
Lastly, the evaluation of the transference of improvement in jump
height in a specific dance skill was not conducted.
CONCLUSION AND PRACTICAL
IMPLICATIONS
A 16-week training program of lower-limb strength training
using mainly own body mass effectively improve CMJ height in
young dancers and can present practical implications for dance
training. Supplementary strength training seems to be effective
for improving jumping performance in ballet dancers.
We suggest that the incorporation of 20 min of strength and
plyometric additional training could improve the jump height of
the ballet dancers.
The design of the training program suggests that this is
possible with no equipment and may be easily incorporated in the
dance training schedule and the typical dancer’s training space.
FUTURE RESEARCH
We suggest more investigation in this area, seeking a better
understanding of the dance physical needs, making more
information available for dance professors to better complement
their training programs. Future studies should aim for a more
individualized, specific, and effective training monitoring and
periodization (e.g., variables measured every 3 weeks during the
program and every week after the end of the individualized
program) (Jiménez-Reyes et al., 2019). It would be important
to assess if the study results could be transferred to perform
ballet-specific skills.
DATA AVAILABILITY STATEMENT
The raw data supporting the conclusions of this article will be
made available by the authors, without undue reservation.
ETHICS STATEMENT
The studies involving human participants were reviewed and
approved by the Ethical Committee, Faculty of Sports Science
and Physical Education, University of Coimbra (CE/FCDEF-
UC/00742021). Written informed consent to participate in this
study was provided by the participants’ legal guardian/next of kin.
AUTHOR CONTRIBUTIONS
LÁ-C, FC, JE-Á, and LR participated in study design, data
collection, and the writing of the first draft manuscript. LÁ-C,
FC, JE-Á, BG, IL, and LR participated in the article collection
and analysis. LÁ-C, FC, JE-Á, IL, and LR participated in the
writing of the methodology and results, and the final revisions
of the manuscript. All authors have read and approved the
final version of the manuscript and agreed with the order of
presentation of the authors.
SUPPLEMENTARY MATERIAL
The Supplementary Material for this article can be found
online at: https://www.frontiersin.org/articles/10.3389/fphys.
2021.774327/full#supplementary-material
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