J. Phys. Ther. Sci.

29: 783788, 2017

The Journal of Physical Therapy Science

Original Article

Effects of short-term plyometric training on

physical fitness parameters in female futsal
athletes

Vincius Fonseca Neves da Silva, BSc1, 2)a, Samuel da Silva Aguiar, BSc3)a,
Caio Victor Sousa, MSc1, 3), R afael da Costa Sotero, PhD2, 4),
Jos Morais Souto Filho, BSc3), Irans Oliveira, PhD4)*, Mrcio R abelo Mota, PhD1, 4),
Herbert Gustavo Simes, PhD3), Marcelo Magalhes Sales, PhD35)
1) Faculdade de Cincias da Educao e Sade, Centro Universitrio de Braslia, Brazil
2) Programa de Ps-Graduao Stricto Sensu em Gerontologia, Universidade Catlica de Braslia, Brazil
3) Programa de Ps-Graduao Stricto Sensu em Educao Fsica, Universidade Catlica de Braslia, Brazil
4) Faculdade de Educao Fsica, UniEvanglica Centro Universitrio: Anpolis, Gois, Brazil
5) Universidade Estadual de Gois, Quirinpolis, Brazil

Abstract. [Purpose] To verify the effects of short-term plyometric training (PM) on body composition, flexibility
and muscle power output in female Futsal athletes. [Subjects and Methods] Twenty female Futsal athletes (19.5
1.29years) equally and randomly divided into control and experimental groups were submitted to a sit-and-reach
flexibility test, body composition measures and horizontal jump, at baseline and one day after the final training ses-
sion. Both groups retained their training routines while only the experimental group participated in an additional 25
minutes of PM 2 times a week over 4 weeks. [Results] The experimental group showed higher values of flexibility
and muscle power and lower body fat after the intervention in comparison to the baseline and control group. In ad-
dition, the effect size within-group after intervention indicated a moderate, large and very large effect for body fat,
flexibility and muscle power, respectively. [Conclusion] These results show that plyometric training may be effec-
tive in reducing body fat and increasing flexibility and muscle power in female Futsal athletes. Thus, it may suggest
that PM can be applied in the field of preventive physical therapy.
Key words: Sport, Body composition, Athletic performance
(This article was submitted Jul. 2, 2016, and was accepted Nov. 18, 2016)

INTRODUCTION
Futsal is an intermittent high-intensity sport characterized by the elevated technical and tactical level of the athletes1, 2).
In addition, because Futsal is a high-intensity sport, physical requirements must be considered when implementing training
programs for athletes of this modality3). Thus, physical training for these athletes is extremely important to maintain the
competitive level in each match throughout the season4), and it is necessary to search for and apply more efficient training
methods. A widely used but less scientifically explored alternative method for Futsal athletes is plyometric training (PM).
PM develops muscle strength, maximum power, speed and explosive anaerobic power5). Furthermore, strength and
muscle power gains promoted by PM seem to be similar to those promoted by resistance training6). However, without the
need for sophisticated and expensive equipment. Making PM an interesting alternative for professional and amateur teams
with a low financial investment for those that appropriate training center often is unavailable. Moreover, added to muscle

aTheseauthors have contributed equally to this work.

*Corresponding author. Irans Oliveira (E-mail: iranseoliveira@hotmail.com)
2017 The Society of Physical Therapy Science. Published by IPEC Inc.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives (by-nc-nd)
License <https://creativecommons.org/licenses/by-nc-nd/4.0/>.
power improvements, this method can also be effective to improve body composition and flexibility parameters because of
the high energy expenditure and range of motion necessary to perform jumping exercises7), which may lead to performance
improvements during the game8). It is noteworthy that the exercises used during PM are part of most of the movements during
sports itself9).
In some studies on female Futsal athletes, this method has already demonstrated to improve muscle power output, muscle
strength and speed8, 10, 11). However, compared to male athletes, few studies have investigated the effects of PM on the
parameters mentioned above. Moreover, to the best of our knowledge, there is only one study that investigated the effects
of PM on body composition in female Futsal athletes8). It is noteworthy that this parameter has been widely accepted as a
predictor of performance1214).
In addition, there are no studies that have investigated the effects of PM on the flexibility levels of Futsal athletes. It should
be noted that this parameter has been associated with performance enhancement and injury prevention by regaining joint
range of motion1517). Therefore, the aim of this study was to verify the effects of PM on power output, body composition
and flexibility in female Futsal athletes.

SUBJECTS AND METHODS

Twenty female Futsal university athletes without any muscle, bone and/or joint limitations, no use of any drugs, had
practiced Futsal for at least 3years and had attended at least 80% of the training sessions were included in the analysis. The
athletes were randomly and equally divided in two groups, the experimental group (EG=10) and the control group (CG=10).
The final sample size (n=20) conferred a statistic power a priori of 60% (1 = 0.6; =0.05). General characteristics of the
volunteers are presented in Table 2. All procedures were carried out according to resolution 466/2012 of the National Health
Council and to the Declaration of Helsinki for experiments to be conducted on humans. This study had approval of the local
Ethics Committee for Human Research (protocol: 21306613.1.0000.0023) and obtained a written informed consent from the
volunteers.
All volunteers were instructed to maintain their dietary habits during the investigation protocol. Both groups (EG and CG)
underwent an evaluation of their body composition (skinfold and waist-to-height ratio), flexibility (sit-and-reach) and muscle
power output (horizontal jump test) at baseline and one day after the 4-week intervention period. During these 4 weeks, both
groups maintained their tactical and technical training routines with specific activities of the modality. Meanwhile, the EG
underwent PM (Table 1) twice a week for approximately 25 minutes per training session. Plyometric exercises were progres-
sive and were adapted from Bompa18).
Height was measured with the volunteer in a standing position and barefoot, with the ankles, calves, buttocks, scapulas
and head leaning against the wall. The head was positioned according to Frankfurts plan, and stature was measured at the
moment of inhaling air. Body mass was measured while the participants wore light clothes. Body mass index (BMI) was
calculated as weight (kg) height (m2).
Relative body fat was estimated by the sum of four skinfolds (subscapular; triceps; suprailiac; abdominal) using a skinfold
caliper (Sanny) and applying the equation and protocol proposed by Falkner19). The skinfolds were collected at each point
in rotational sequence, beginning on the right side of the body, and the median value was recorded (Table 2).
Flexibility of the hamstrings and lower back muscles was evaluated by the sit-and-reach test20). Individuals were placed
in a seated position with legs straight and slightly parted, feet flat on the wall of the wooden box (Wells Bench), elbows
extended and upper limbs flexed in the sagittal plane. From this position, individuals were instructed to stretch forward over
the box and attempt to reach with their hands as far as possible on a graduated scale in centimeters at the top of the box. The
largest absolute value over three attempts constituted the measurement of flexibility.
Participants began the test with both feet parallel on a marked line and were instructed to perform three maximum jumps to
cover the greatest horizontal distance possible. Using a floor mounted tape measure, the distance covered by each jump was
determined from the start line to the where the heel closest to the start line landed. We recorded the best jump performance
value21).
After assessing the normality and homogeneity of the data through the Shapiro-Wilk and Levenes test, respectively, the
data were presented as the mean and standard deviation (). In order to compare the characteristics of the groups, Students
t-test for independent samples was applied. Between and within-group comparisons were carried out using split-plot ANOVA
(Mixed ANOVA). When any of the dependent variables did not show sphericity in Mauchlys test, the epsilon of Greenhouse-
Geisser was used to analyze the F statistic. Because there were only two groups, a post hoc test was unable to locate the
differences; it is necessary to apply a parallel test called pairwise comparisons. Thus, a paired Students t-test was used to
compare the values at baseline and after the intervention period. The effect size within (baseline vs. post) and between groups
(EG vs. CG) was calculated using Cohens d22). Pearsons correlation coefficient was applied to test for associations between
the variables. For the sample size calculation, was used the statistical power (1-) a priori using the comparison analysis ap-
plied (ANOVA for repeated measures), an effect size of f=0.35 and, significance level set at 5% (p<0.05) to all procedures. All
procedures were carried out using the Statistical Package for the Social Sciences (SPSS 20.0) and G*Power (version 3.1.9.2).

784 J. Phys. Ther. Sci. Vol. 29, No. 5, 2017

 RESULTS
At baseline, the groups (EG and CG) presented no statistical differences among the variables of characterization, with the
exception of body fat, that showed lower values for the EG (Table 2). In contrast, both groups were classified in the same
stratum (excellent) for body fat, taking into account sex and age23). The within-group comparisons indicated a significant
reduction in the body fat and an improvement in flexibility and muscle power output for the EG (p<0.05). Furthermore, the
between-group comparison indicated that the EG had significantly lower post-intervention values for body fat and signifi-
cantly higher values for power and flexibility (Table 3).
The within-group comparison of the effect size showed that the CG values did not change significantly in all of the inves-
tigated variables; meanwhile, the EG displayed effects of moderate, large and very large standards for body fat, flexibility and
muscle power, respectively. In the between-group comparison of the effect size, only the waist-to-height ratio (WHR) had no
effect (d=0.16), while there was a large effect for the body fat (d=1.11), and a very large effect for flexibility (d=2.09) and
for muscle power (d=2.55) (Table 3).
Pearsons correlation coefficient indicated a positive and significant (p<0.05) association between baseline values of
flexibility and post-intervention horizontal jump and flexibility. In addition, the results showed a negative and significant
association between baseline flexibility and post-intervention body fat. Furthermore, a negative and significant association
was found between baseline body fat and post intervention horizontal jump and flexibility (Table 4).

Table 1. Description of the plyometric training exercises performed

Planning Number of series and

Description
(training session) repetitions (reps)
Week 1
Alternate leg bounding; unilateral squat jump; power skipping 4 (15 reps) in each exercise
( 25 minutes)
Week 2
Power skipping; squat jump; alternate leg bounding 3 (815 reps) in each exercise
( 20 minutes)
Week 3 Squat jump; repeated long jumps; unilateral squat jump; static tuck
3 (815 reps) in each exercise
( 15 minutes) jumps
Week 4 Progressive power skipping; rhytm skips; jump rope (30 seconds); 23 series: circuit with 90
( 15 minutes) unilateral squat jump; diagonal obstacle jump; repeated tuck jumps seconds interval

Table 2. Sample characteristics Table 3. Within- and between-group comparisons of waist-to-

height ratio, body fat, sit-and-reach and horizontal jump
Control Plyometric training
(n=10) (n=10) Control Plyometric
Age (years) 19.5 1.4 19.4 1.3 training
Height (cm) 165.1 5.8 161.1 9.6 Waist-to- Baseline 0.44 0.03 0.44 0.10
Body mass (kg) 62.5 8.8 59.8 8.7 height ratio Post-training 0.44 0.01 0.45 0.10
BMI (kg.m2) 23.5 2.7 22.1 0.9 Effect size 0.1 0.1
Body fat (%) 16.5 1.8 15.1 3.2 * Body fat Baseline 16.5 1.8 15.1 3.2
WHR 0.44 0.0 0.44 0.1 (%) Post-training 16.5 1.8 13.9 2.9 *
Data expressed as mean and () SD Effect size 0.02 0.39
BMI: body mass index; WHR: waist-to-height ratio; *Sta- Flexibility Baseline 24.9 3.7 31.6 5.1
tistical difference (p<0.05) (cm) Post-training 25.0 3.7 35.6 4.6 *
Effect size 0.01 1.99
Horizontal Baseline 133.1 22.4 151.1 8.8
jump (cm) Post-training 132.9 23.0 170.4 10.5 *
Effect size 0.02 0.81
Within-group comparisons effect size estimated by Cohens d.
Data expressed in mean and standard deviation.
*Within-group statistical difference (p<0.05); Between-group
statistical difference for the same moment (p<0.05).

785
 DISCUSSION
The aim of this study was to investigate the effects of four-week-long PM on physical fitness parameters. The main finding
was that, in addition to muscle power, PM was also effective to promote an increase in flexibility levels and reduce body fat
in young female Futsal players.
The high-intensity stretch-shortening cycles performed during PM may cause several peripheral adaptations, such as
muscle hypertrophy. Malisoux et al.7) submitted eight trained men to eight weeks of PM and reported a significant increase
(p<0.01) in the cross-sectional area of muscle fibers type I and IIa of the vastuslateralis. An increase in muscle mass may lead
to a higher resting metabolic rate and promote higher energy expenditure at rest, which may lead to other changes in body
composition over the medium and long term, such as a decrease in body fat24). Similarly, it was observed in the present results
(p<0.05), which showed a moderate and large effect in the comparisons within-groups (baseline vs. post) according to the
Cohens standard22). It is important to emphasize that an improvement in body composition parameters can be fundamental
for the performance of athletes during the match, especially Futsal, since this sport involves rapid movements and jumps and
the direction changes continuously; any excess body weight or fat may influence the athletes general performance25).
With regard to WHR, the results demonstrate that it remained unchanged after PM in both groups, which may be because
young athletes, such as those used in this study, have absolute mean values of this index below the average and median
compared to reference values for this age26). Thus, are not very susceptible to a reduction along with other body composition
parameters.
Flexibility improvement for Futsal athletes after PM is an important finding because the deficit of this physical fitness
component has been postulated as being responsible for muscle and joint injuries in the lower limbs in athletes and recre-
ational players27). Thus, alternative training methods that may reduce the risk of injury may be of interest to teams, coaches
and athletes28). OSullivan et al.29), reported evidence that a training method focused on eccentric contractions can raise
flexibility levels in the lower limbs and suggests that the most likely mechanism involved may be the increase of sarcomeres,
a phenomenon already observed in animal models30). Therefore, the flexibility gains in this study may be explained on ac-
count of PM having a large eccentric component in its repeated high-intensity stretch-shortening cycles7), promoting similar
adaptations to those suggested above.
Regarding to PM, studies have focused on analyzing the effects on the injury prevention of first time non-contact anterior
cruciate ligament (ACL) injury. The result indicates that PM can enhance neuromuscular control in all three planes, which
will reduce stress on the ACL transferring to the muscles, tendons and bones, allowing a greater dispersion of force resulting
in lower torque applied directly to the knee3134).
The primary focus of PM is commonly associated with muscle power improvement, which may be occasioned for several
of factors. The increase in muscle power can be explained in part by the fact that PM increases the muscular tension reducing
the energy dissipated by the tendon, by an improvement in tensile strength35). Moreover, a simple increase in motor skills to
perform horizontal jumps may be one a factor improving jump performance because this movement-jump is classified as a
slow shortening-stretching cycle with high range of motion36) and has been suggested as being the most responsive to PM37).
In addition, the reduction in body fat and increase inflexibility levels could also be responsible for higher muscle efficiency
and range of motion, respectively. Increasing the ability of athletes to have a higher power output and achieve better results
in the horizontal jump test. The association results may reinforce this because the increase in muscle power after intervention
was negatively associated with body fat reduction and positively associated with increased flexibility. Furthermore, PM has
shown improvements in muscle power of the lower limbs for athletes in several sports38), including Futsal. Almeida and
Rogatto11) demonstrated a 10% increase of muscle power in female Futsal athletes, similarly to the present study, which
demonstrated an increase of 12%.
Studies suggest that an increase in muscle strength and flexibility may significantly reduce the likelihood of injury3945).
Furthermore, the excess weight has been considered a risk factor for lower limb injuries in sports27, 46, 47). Thus, the results of

Table 4. Matrix correlation between baseline and post intervention values of body fat, horizontal jump (power) and
flexibility of the experimental group

Baseline Post intervention

Power Flexibility Body fat Power Flexibility
Baseline Body fat 0.3 0.6 * 0.9 * 0.7 * 0.8 *
Power - 0.2 0.2 0.7 * 0.2
Flexibility - - 0.7 * 0.6 * 0.9 *
Post Body fat - - - 0.7 * 0.8 *
intervention Power - - - - 0.7 *
Data expressed as Pearsons coefficient r (p value).
*Significant correlation (p0.05).

786 J. Phys. Ther. Sci. Vol. 29, No. 5, 2017

this research may suggest that PM can be applied in the field of preventive physical therapy.
Further, the results may still be relevant for teams and coaches who seek simple, low-cost and efficient methods to
optimize the physical training of their athletes and may even be an alternative to resistance training, which can be costly
for professional and amateur teams with a low financial budget and who have no access to sophisticated equipment. In this
regard, MacDonald et al.6) submitted 30 trained men to six weeks of PM or two different methods of resistance training, and,
although improvement was reported in all groups for anthropometric measurements (thigh and calf circumference, body fat)
and strength (Romanian deadlift; standing calf-press) in the within-group comparison, there were no differences between the
groups, suggesting similar adaptations of plyometric and resistance training.
The fact that we have not investigated the mechanisms that may be involved in the improvement of the investigated
variables (muscle power, body composition and flexibility) and that there was no nutritional control, can be considered
limitations of this research. Nevertheless, all volunteers were instructed to retain their food intake patterns throughout the
study. Furthermore, the fact of body fat have shown significant difference between groups at baseline, can also be configured
as a limitation. However, it is noteworthy that both groups were classified in the same stratum (excellent) for body fat,
considering the gender and age23). Moreover, relative small sample size may also characterize a limitation. Thus, we suggest
that the findings of this study should be interpreted with some caution.
Therefore, in addition to muscle power and strength improvements that PM may promote, this simple and low-cost
method can also be effective in improving other parameters of physical fitness and can be an alternative for athletes and
coaches during physical preparation. In summary, these results concluded that PM seems to be effective to reduce body fat
and raise flexibility and muscle power levels in female Futsal athletes.

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