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“Effect of plyometric training on sprint and change of direction speed in young basketball athletes”
Introduction
Background Information
Basketball is an intermittent high intensity sport that requires high levels of technical skill and
conditioning in order to efficiently perform. As the athlete increases their level of physical conditioning,
they are generally able to handle a higher level of physical demand. Sprint and change of direction (COD)
ability has been found to directly influence sport performance, and it is suggested that a basketball
athlete will perform anywhere between 55-124 sprints in a single game, all while having to execute
numerous sport-specific tasks (i.e. dribbling and offensive/defensive transitions). In an effort to improve
the physical conditioning and readiness of basketball athletes, many training methods have been
studied, with plyometric training (PT) being one of the most utilized. Based on the optimization of the
stretch-shortening cycle (SSC), benefits of PT in relation to feasibility include the ease of application,
minimal cost, and ability to be conducted in virtually any environment.
Several adult athlete studies have found that PT has a positive effect on both sprint ability and
the speed of COD. However, results among youth athletes in studies investigating similar effects have
been scarce and conflicting. Opposing studies by Thomas et al in 2009 and Hammami et al in 2016
investigated the effects of PT on sprint ability in youth soccer athletes. While Thomas et al found that a
six week intervention did not significantly improve 5-30 m sprint performance, Hammami et al found
that 5-20 m sprint performance did significantly improve after an eight week intervention. In congruence
with Hammami et al, several other studies have yielded positive effects on sprint performance after a PT
intervention. In relation to COD speed, opposing results between studies have also been noted. While
Gottlieb et al in 2014 found no significant improvements in both COD speed and sprint performance
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after a six week intervention in youth basketball athletes, Bougezzi et al in 2020 noted a positive
influence of PT on COD speed after an eight week intervention in youth soccer athletes.
Purpose/Hypothesis
Because of these conflicting results among previous research, the purpose of this study was to
verify the effects of a six week PT intervention on sprint performance and COD speed in youth basketball
athletes. It was hypothesized that PT would contribute to an improvement in both sprint and COD ability
in the participants.
Methods
Subjects
39 youth athletes (16 male, 23 female) participated in this study. Each sex was analyzed
separately, with male and female groups being randomly divided in experimental (EG) and control (CG)
groups. The male experimental group (MEG) consisted of six athletes (15.83±.75 yrs, 1.83±.07 m,
70.78±11.83 kg) and the male control group (MCG) consisted of seven athletes (15.43 ± 1.13 yrs, 1.74 ±
0.13 m, 72.94 ± 24.13 kg). The female experimental group (FEG) contained 11 athletes (14.45 ± 0.69 yrs,
1.60 ± 0.07 m, 53.72 ± 9.01 kg) while the female control group (FCG) had 10 athletes (15.30 ± 1.16 yrs,
1.63 ± 0.08 m, 59.98 ± 16.74 kg). Inclusion criteria for this study was as follows: linked to the National
Confederation of Basketball, 1+ year of experience with physical training, and no muscle injuries that
would prevent them from participating in the study’s activities with maximal effort. Potential participants
were excluded if they did not attend at least 75% of the interventional training sessions and/or
presented injuries at any point during the study application period. Participation in this study was
voluntary, and participants signed an informed consent form after being informed about the potential
risks and benefits of the study.
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Protocols
This study utilized a longitudinal research design that was implemented during the pre-training
period of the athletes’ season, lasting a total of eight weeks (two for testing, six for the PT intervention).
During the first week, anthropometric and physical tests were performed, being preceded by a
familiarization period of the testing procedures in order to avoid the learning effect. The physical tests
utilized in this study were a 20 meter sprint (Sp20m test) and the Illinois agility test (IAT). The Sp20m test
was conducted on an indoor basketball court, where the best attempt of three trials (measured via a
manual stopwatch) was used for analysis. A five minute break was given between each sprint to allow for
full recovery. The IAT was performed in much the same way as the Sp20m test, where the athlete started
on a voice command and the best of three trials was used. They were also allowed a five minute rest
between trials during the IAT assessment.
During weeks 2-7, the EGs were assigned a combination of PT and regular basketball practices,
while the CGs only conducted regular practices. The EGs performed PT and basketball training on non-
consecutive days, with PT occurring twice per week and basketball training occurring three times per
week. It is important to note that during each PT session, all jumps performed by the athletes were
guided and supervised by the technical committee. The interventional PT program consisted of a
combination of various types of jumps, including the countermovement jump, side jump, horizontal
jump, high knee jump, split squat jump, serial forward hops, single leg vertical jump, and single leg
lateral hops. A 10-minute warm up preceded each PT session, consisting of light running and dynamic
stretches. The PT sessions lasted between 30-60 minutes and occurred before practice. The volume of PT
was quantified by the number of jumps performed during each week, with the total number of jumps
gradually increasing over the course of the intervention in order to promote adaptations via increased
training volume. Within a given PT session, athletes were given a 30 second rest between individual
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jumps (for all except the serial forward hops) and 120 seconds of rest between series/sets. Basketball
training utilized by both EGs and CGs involved a 90 minute training session that consisted of small-side
games and offensive/defense tactical training. During the final week of the intervention (week eight),
physical reassessments were performed.
Statistical analysis was conducted via SPSS software, where values were expressed as mean plus
standard deviation and the alpha level of significance was set at p<0.05. A Shapiro-Wilk test was used to
test normality of the data, and a repeated measures ANOVA was performed to compare the results of
pre- and post-intervention tests. The effect size was calculated based on Cohen’s D.
Results
For both MCG and MEG groups, significant improvements occurred between pre and post
testing for both Sp20m (p=.006) and IAT (p=.002). MEG Sp20m times improved from 3.61±0.14 s to
3.46±0.16 s, and IAT times improved from 16.95±0.75 s to 16.33±0.85 s. MCG Sp20m times improved
from 3.59±0.24 s to 3.52±0.29 s, and IAT times improved from 17.73±1.22 s to 17.38±1.72 s. For the
female groups, both FEG and FCG groups significantly improved their Sp20m test values (p=.008), while
neither group significantly improved their IAT values (p=.86). FEG Sp20m times improved from 3.77±0.29
s to 3.50±0.76 s, and FCG Sp20m times improved from 3.97±0.40 s to 3.85±0.38 s. Although not a
statistically significant improvement, both groups did increase their IAT values. Respective IAT pre to post
values for FEG was 17.88±0.74 s and 17.47±0.77 s, while respective pre and post values for FCG was
18.64±1.51 s and 18.43±1.30 s. An analysis of percent change of Sp20m test yielded values for MEG (-
4.15%), MCG (-1.94%), FEG (-7.16%), and FCG (-3.02%). Additionally, for the IAT, the analysis of percent
change yielded values for MEG (-3.65%), MCG (-1.97%), FEG (-2.29%), and FCG (-1.12%).
Discussion
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The findings of this study revealed that, although both EGs and CGs improved their Sp20m
performance, the PT intervention led to more significant improvements on Sp20m for both sexes.
Additionally, greater improvements in IAT occurred in the MEG compared to the MCG, even though both
groups significantly improved. Neither female group significantly improved their IAT scores. However,
both groups did improve, with the FEG experiencing greater effects. When analyzing the percent of
change between pre and post Sp20m scores, there was an improvement of 7.16% for the FEG with a
large effect size (ES=0.96). This result agrees with a previous finding from Idrizovic et al in 2018 that
found a statistically significant improvement of 5.7% in Sp20m values after a 12 week PT intervention in
youth volleyball athletes. The MEG significantly improved their Sp20m time by 4.15%, yielding a large
effect (ES = 1.07). This finding agrees with a previous study by Chaabene and Negra in 2017 that found
significant improvements in 10 m, 20 m, and 30 m sprint times after both low and high volume PT. It is
important to note that although the EGs had more significant improvements in Sp20m times, basketball
training by itself (in the CGs) was still found to positively influence Sp20m values. MCG improved by
1.94% (ES = 0.29) and FCG improved by 3.02% (ES = 0.30). The more significant improvements brought
on by the PT intervention can be explained by neuromuscular factors (i.e. increased stretch reflex and/or
muscle elasticity, inhibition of the Golgi tendon organs) that are potentiated by plyometrics that may
promote a decreased ground contact time during sprinting.
In relation to sprint ability, this study also found that COD speed significantly increased for both
MEG (3.65% improvement, ES = 0.82) and MCG (1.97% improvement, ES = 0.28) during the IAT. However,
because of the low effect size for MCG, generalization of results would be difficult based on the findings
of this study. There is scarce literature on the effects of PT on COD speed in youth basketball athletes so
comparisons to previous studies cannot be made. Only the MEG showed a significant improvement and
wide effect size on the IAT, although all groups improved their IAT times between pre- and post-testing. A
study by Ramirez-Campillo et al in 2014 agreed with this study’s hypothesis with an observed 3.5%
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improvement on IAT after implementing a seven week PT intervention for youth soccer athletes.
Improvements in IAT may also be explained by neural adaptations from PT, including improved muscular
coordination and greater motor unit recruitment. In agreement with a study by Meszler and Vaczi in
2019, which found that there were no significant improvements in IAT times in both FEG and FCG,
neither female group significantly improved in this study. However, although not statistically significant,
both female groups did still improve, meaning practical implications should be considered.
This study showed similar results to numerous other previous studies, showing important results
in the realm of training for sport, but certain limitations were still present. The smaller sample size
(n=39) makes it difficult to generalize results. Additionally, the investigators did not assess the athletes’
internal load or biological maturation, which may have impacted the results and/or conclusions of this
study. Finally, with a handheld time measurement device (manual stopwatch) being used, there was
potential for intrarater error. Although the results may have been reliable, they may not have been fully
accurate, putting into question the validity of the results. However, even if there was an estimated error
from manual time measurements, it may not have been relevant enough to significantly alter the
findings of this study. Additionally, for feasibility purposes, the investigators may not have had access to
radar-facilitated time measures. In response to the limitations presented, future studies should
investigate both biological maturation and internal load when analyzing the effect(s) of a PT intervention
to better understand the factors that influence performance. Also, a larger sample size or replication
study would be beneficial to confirm the results of this study. The influence of PT on other physical
abilities (i.e. vertical/horizontal jump, strength balance, and anaerobic resistance) should also be
investigated in more depth for youth athletes across different sports.
Based on the results of this study, it is possible to conclude that a six week PT intervention
promoted significant improvements in Sp20m and IAT values in MEG. Additionally, the FEG achieved
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more significant improvements in sprint performance and greater effects in COD ability when compared
to the FEG. These results indicate that improved physical conditioning (specifically sprint and COD ability)
in youth athletes of both sexes may be facilitated through the application of plyometrics in a training
regimen.
Analysis and Critique
This study provides good insight into the effect that PT has on sport performance, specifically on
sprint and COD ability. It is surprising that there is a scarcity of studies investigating the potential effects
of PT on youth sport performance. There is ample evidence about the relative safety of PT in youth
athletes as long as proper protocol and progression is followed. Because of this, researchers need to be
more willing to investigate this relationship. Specific to this study, although positive results were found
for both sprint and COD ability, a longer interventional period should have been implemented based on
the findings from the literature review. In the studies discussed in the introduction, those that found no
significant improvements in sprint and/or COD ability implemented only a six week PT intervention,
while the studies that found significant improvements in one or both abilities implemented an eight
week intervention. While this may have been nothing more than coincidence, it may point to the need to
investigate how the length and/or intensity of a PT intervention affects the magnitude of improvements
in sprint and COD ability. Establishing a dose response relationship could be incredibly beneficial for both
future studies and training implications on team sport athletes.
In relation to the results of this study, positive results were identified for both sexes in all groups.
It was concluded that a greater magnitude of improvement in both sprint and COD ability occurred in the
intervention groups. Despite this fact, both control groups still improved their scores for both physical
tests, which speaks to the importance of task/sport-specific training on sport performance. However,
because there were more significant improvements in the EGs, it can be suggested that the PT program
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prescribed was sufficient to facilitate neuromuscular adaptations associated with plyometric ability.
Future studies implementing similar strategies and/or testing measures should consider variations in the
specific PT programming to investigate whether the use and/or progression of other plyometric exercises
would have a different magnitude of effect on sport performance.
Practical Applications
The results of this study suggest the importance of plyometrics in training programs of team
sports for youth athletes. Because of the explosive nature of most all team sports, training in an
explosive, power-emphasis manner is essential. Simply put, if athletes do not train to be explosive, they
will not be explosive. This study used only a six week intervention and still found improvements in both
sprint and COD ability. Implications for training programs based on these results suggest that it may not
take long interventional programs to significantly improve an athlete’s ability to perform. This becomes
increasingly important as the team sport season progresses from pre-season to and throughout the
competitive season, as the duration and/or frequency of training generally declines as the season
progresses further to manage overall volume load and mitigate the risk of non-functional overreaching
and/or overtraining. By establishing a minimum effective dose that would still yield improvements in
sport performance, the coach can more efficiently be able to periodize a program for their specific sport.
By combining technical training with PT and/or other forms of performance-based resistance training,
athletes may be able to continually progress (or at least maintain) their performance abilities as the
season progresses without falling victim to symptoms of burnout or overtraining. Additionally, this study,
as well as those referenced, suggests the relative safety and efficacy of PT programs on youth athletes. In
my personal experience, some populations (most likely uninformed and/or unknowledgeable) have
placed a negative stigma on plyometrics and/or other forms of resistance training for young individuals,
stating that training of that kind will stunt their growth or lead to long-term issues. While improperly
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implemented resistance training can definitely lead to injury or stunted growth, there is safety in youth
populations performing resistance training when a needs analysis has been performed. This study
appeared to do a good job in minimizing risk of injury to the youth participants through constant
supervision and guidance before and during jumping task execution. Especially in those unfamiliar with
specific exercises, proper coaching instruction can make the difference between effective improvements
in technical/performance ability and injury development. This study should be expanded upon to include
an investigation on the effects of PT on other physical aspects within this population.
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Reference
Paes, P. P., Correia, G., Damasceno, V. O., & Lucena, E. V. (2022). Effect of plyometric training on sprint
and change of direction speed in young basketball athletes. Journal of Physical Education and
Sport, 22(2), 305–310. https://doi.org/10.7752/jpes.2022.02039
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