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NR 49
AN TRO PO MO TO RY KA
2010
THE INFLUENCE OF PLYOMETRICS TRAINING
ON THE MAXIMAL POWER OF THE LOWER LIMBS
IN BASKETBALL PLAYERS AGED 16–18
WPŁYW TRENINGU PLAJOMETRYCZNEGO NA POPRAWĘ
POZIOMU SIŁY EKSPLOZYWNEJ KOŃCZYN DOLNYCH
U KOSZYKARZY W WIEKU 16–18 LAT
Ryszard Litkowycz *, Kajetan Słomka **,
Monika Grygorowicz ***, Henryk Król****
*****Dr, Chair of Team Sports, the Jerzy Kukuczka Academy of Physical Education in Katowice
*****Dr, Department of Human Motor Behavior, the Jerzy Kukuczka Academy of Physical Education in Katowice
*****Dr, Department of Physiotherapy, the Stanisław Staszic State School of Higher Vocational Education in Piła
*****Dr, habil., Department of Human Motor Behavior, the Jerzy Kukuczka Academy of Physical Education in Katowice
Key words: basketball, training, playometrics
Słowa kluczowe: koszykówka, trening, plajometryka
SUMMARY • STRESZCZENIE
– 33 –
-
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Cel pracy. Celem pracy było określenie dynamiki zmian siły eksplozywnej przejawiającej się w biegach i skokach u koszykarzy w wieku 16–18 lat pod wpływem treningu plajometrycznego. Koszykówka należy bowiem do
tych dyscyplin sportowych, w których dominującą rolę odgrywa zdolność motoryczna o charakterze siłowo-szybkościowym, a w konsekwencji – siła eksplozywna. Dzięki niej nie tylko koszykarze, ale także przedstawiciele innych
dyscyplin sportowych mogą pokazać pełnię swoich umiejętności techniczno-taktycznych.
Materiał i metody. Badaniom poddano 36 koszykarzy w wieku 16–18 lat, podzielonych na grupę eksperymentalną i kontrolną. Przed eksperymentem oraz po jego zakończeniu dokonano pomiarów szybkości biegowej
(na dystansach 5, 15, 20 i 30 m), wytrzymałości szybkościowej (bieg 10 × 30 m), siły dynamicznej kończyn dolnych
-
-
Aim of the work. The study was aimed at assessing the influence of plyometric training on explosive strength
development dynamics in running and jumping among basketball players, since basketball is a sport discipline
dominated by strength and speed abilities. The combination of these two constitutes explosive strength enables
the athletes of various sport disciplines to perform at the highest level of their technical and tactical skills.
Material and methods. Thirty-six basketball players aged 16–18 participated in the study. They were divided
into experimental (E) and control (K) group. Running speed (5 m, 15m, 20m and 30m distance), speed endurance (10 × 30 m run), explosive strength of trunk and legs (recorded on a dynamometric platform) as well as
strength endurance of leg flexors and extensors in isokinetic conditions were measured at the beginning and
at the end of the experiment.
Results. The training regimen did not result in any significant changes in the examined motor abilities of
basketball players in the control group. The introduction of plyometric training in the experimental group resulted
in a statistically significant strength torque increase in knee flexors and extensors of both joints (measured
at 60º/s, 120º/s, and 240º/s angular velocity). Moreover, changes were observed in the conventional ratio of
hamstrings and quadriceps muscles of the right extremity. Specific training activities positively influenced the
speed endurance assessed with the use of a shuffle run (10 × 30 m). There were no significant differences in
the level of running speed and explosive strength of legs.
Ryszard Litkowycz, Kajetan Słomka, Monika Grygorowicz, Henryk Król
i tułowia (platforma dynamometryczna), siły dynamicznej oraz wytrzymałości siłowej prostowników i zginaczy stawu
kolanowego w warunkach izokinetycznych.
Wyniki i wnioski. Trening sportowy nie wywołał istotnych zmian u koszykarzy z grupy kontrolnej w zakresie
badanych zdolności motorycznych. Wprowadzenie ćwiczeń plajometrycznych do treningu koszykarzy z grupy
eksperymentalnej w większości przypadków doprowadziło do istotnego statystycznie wzrostu wartości momentu
siły zginaczy i prostowników stawu kolanowego kończyny dolnej prawej i lewej (60º/s, 120º/s, 240º/s). Ponadto
stwierdzono zmiany w proporcjach wartości momentów sił zginaczy i prostowników stawu kolanowego kończyny
dolnej prawej. Specyficzne zajęcia treningowe wpłynęły na istotną poprawę wytrzymałości szybkościowej ocenianej
biegiem wahadłowym 10 × 30 m. Nie stwierdzono różnic, bądź też występowały sporadycznie w poziomie szybkości
biegowej (5, 15, 20 i 30 m) oraz mocy kończyn dolnych (platforma dynamometryczna).
to a very intensive muscle contraction – the concentric (overcoming) phase [4, 8–11]. The most important
discovery of the plyometric training was that it not only
develops the muscle tissue but above all, it improves
the coordination of the whole neuromuscular system.
Previous research results [6, 5, 10, 12–22] on plyometric training and relation between strength and speed
abilities inspire to further studies. The aim of our experiment was to assess the influence of plyometric training
on the explosive strength change dynamics, evident
in running, jumping and in muscle torque values measured in isokinetic conditions.
Introduction
-
-
Time[s]
Practical experience and various test results prove that
speed-strength abilities are one of important motor
abilities for an athlete, particularly for a basketball player
[1–8]. Modern sport training practice attributes particular
importance to strength developing exercises (dynamic,
explosive). Apart from the classic methods of shaping
muscle dynamics, plyometrics is an important form of
sport performance. The term “plyometrics” comes from
the Greek words “plio” and “metric”, meaning “more” and
“measure”, respectively. The first reports about the methods and concept of plyometric exercises were provided
by the coaches from the former USSR, as described by
Donald and Chu [4] and Mikołajec and Rzepka [8].
Explosive force is based on a phenomenon known in
the literature as the “stretch reflex”, “muscle spindle reflex” or “myotatic reflex”. Rapid muscle elongation due
to a load (eccentric or landing phase) influences the
stretching of fibers responsible for generating energy
necessary for a contraction, which causes the activation of muscle spindles. Muscle spindle stimulation
leads to the stimulation of the spinal cord, and next,
-
Basketball players from the team AZS Katowice who
participated in youth basketball league in two age
groups: older juniors (19–20 years old) and juniors
(17–18 years old) took part in the study. The players
were divided into two groups (experimental and control
one) according to their training skills and age; more experienced players, able to handle larger training loads,
were assigned to the experimental group (Fig. 1). The
1,45
1,43
1,41
1,39
1,37
1,35
1,33
1,31
1,29
1,27
1,25
E I
E I I
KI
KII
1
-
Material and methods
2
3
4
5
6
7
8
9
10
R u nn um ber
Fig. 1. Comparison of mean time in 5m run for the experimental (E) and control (K) group before (I) and after the experiment (II)
– 34 –
The influence of plyometrics training on the maximal power of the lower limbs in basketball players aged 16–18
Table 1. Material
-
-
-
-
-
Group
Category
Number
of players
x± S
min – max
Training
advancement
[years]
Age [years]
Experimental (E)
Juniors
18
16,8 ± 1,2
15,3 – 18,3
6,2
Control (K)
Juniors
18
15,8 ± 0,8
14,5 – 16,4
4,7
experiment lasted from January 30 2006 to June 2
2006, and it was divided into preparation – introduction phase (8 weeks) and experiment proper phase
(I and II, 8 weeks). The aim of the preparation phase,
during which the subjects trained twice a week (using their own bodyweight, mats, and exercises with
a partner) was to develop athletic prowess and practice the correct take-off technique in jump exercises.
The experiment proper I (4 weeks) aimed at building
explosive leg strength through the application of selected plyometric exercises. In the experiment proper II
(4 weeks) training loads were increased on the basis of
individual abilities of the players. To achieve that, basketballs as well as 1 kg and 4 kg medicine balls were
used in plyometric training. The number of jumps was
also increased, but the structure of particular training
units did not change. The microcycle structure details
in the experiment proper phase I and II are presented
in Table 2.
Motor ability level was assessed prior to (on 25
March 2006) and after the experiment completion (on
24 June 2006), with the following research tools:
1. Laser diode system LDM 300C-Sport, used to assess:
– running speed at 5m, 15m, 20m and 30m
– speed endurance in 10 × 30m run.
2. KISTLER dynamometer platform with MVJ [23]
software, used to assess:
– explosive leg and trunk strength measured by
vertical jump with no arm swing.
3. EN-Knee isokinetic dynamometer (Enraf Nonius,
Holland) used to estimate the values of:
– dynamic strength of knee flexors and extensors at 60º/s angular velocity (5 repetitions) and
120º/s angular velocity (10 repetitions) as well
as the conventional muscle torque ratio of knee
flexors and extensors,
– strength endurance of knee flexors and extensors at 240º/s angular velocity (15 repetitions)
as well as the conventional muscle torque ratio
of knee flexors and extensors.
The dynamometer had been used in previous research [24], and the evaluation of the muscle dynamic
potential in isokinetic conditions (including warm-up,
stabilization, rest period) was performed according to
methodology described by Grygorowicz [25].
Descriptive statistics was used in data analysis. It
was found out that the empirical data distribution was
close to normal, which allowed for the analysis of variance (ANOVA) with repeated measures. Since the
condition of data globosity was not fulfilled, the multifactor analysis was used. To assess the significance
between respective test differences post hoc Tukeys’
test was done. To compare related pairs from test I and
II, the Wilcoxon Matched-Pairs Ranks test was used.
Statistical significance was set at p < 0.05. Statistica 5.0
software was used for statistical analysis.
Results and discussion
The study confirmed the effectiveness of the specific
plyometric training. Subjects from the experimental
group obtained significant improvement in the majority
of analyzed variables. In the control group, comparing
the results before and after the experiment, differences
appeared in motor abilities levels; however, they were
not statistically significant (p > 0.05) (Table 3–12, Fig.
1, 2).
Elevating the center of body mass during a vertical jump on spot with no arm swing may be the basis
for an estimate of leg and trunk strength-speed ability
level in basketball players [26]. The obtained data did
not show any significant difference in explosive leg and
trunk strength measured on a dynamometer platform
(Table 3).
The analysis of strength abilities test results performed before and after the experiment in isokinetic
conditions showed an improvement of strength level
in the experiment group, and in the majority of players
the difference was statistically significant (Table 4–8).
The most noticeable is the significant difference in the
level of knee flexor strength at all tested angular veloci-
– 35 –
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-
-
– 36 –
Technical exercises with balls 15min
Strength exercises with medicine
balls (1kg) 15 min
– “multiple jumps”
– “standing jumps”
– “jumps on spot”
(benches, lines, “hexagon”)
– “depth jumps” (with the use of 3 vaulting
boxes and hurdles)
Day off
Day off
4
5
6
7
Phase I
Day off
Day off
1 min after each 3
jumps
4 times longer than
exercise
Day off
1 min after each 3
jumps
4 times longer than
exercise
All jumps total (8 weeks of experiment)
Day off
Day off
Day off
Day off
Strength exercises with medicine
balls (1kg) 15min
– “depth jumps” (with the use of 3 vaulting
boxes and hurdles)
2
3
Constant run
10-15min
Warm up
– “core stability”
on unstable ground (mats),
– “bounding”
Training methods
1
Day of the
week
Table 2. Microcycle structure
-
Phase II
Day off
Day off
2 min after each 3 jumps
5 times longer than
exercise
Day off
2 min after each 3 jumps
5 times longer than
exercise
Rest period
0
0
60
140
0
60
120
Phase I
0
0
60
200
0
60
220
Phase II
Load
(number of jumps)
3266
0
0
658
1182
0
353
1075
Load total
(no of jumps)
5 ,2
Time[s]
5 ,1
5
E I
4 ,9
E II
K I
4 ,8
K II
4 ,7
4 ,6
1
2
3
4
5
6
7
8
9
10
R un n um b e r
Fig. 2. Comparison of mean time in 30m run for the experimental (E) and control (K) group before (I) and after the experiment (II)
ties, both in left and right extremity (Table 4, 5). Identical
number of jumps performed by both lower extremities in
the proper phase of the experiment resulted in a greater
strength increase in the right knee flexor. The strength
level of knee extensor increased as well, however not at
all tested velocities; no significant difference was recorded in the dynamic strength of the lower right extremity
(tested at 60º/s and 120º/s angular velocity) or left extremity (tested at 60º/s angular velocity) (Table 6, 7).
Before the experiment, at 60º/s and 120º/s angular
velocity, the strength level of right knee extensor in basketball players was on a similar level to the strength level
of left knee extensor; only the level of strength endurance
of left knee extensor was slightly higher than that of the
right knee extensor. It seems that the right lower extrem-
ity is more often used to perform the long step in layup
(opposing and take-off phase) while the left lower extremity makes a short dynamic step (take-off phase). As
a result of the plyometric training there was a change in
strength endurance (tested at 240º/s angular velocity) of
knee extensors in both lower extremities. Changes in
dynamic strength levels were observed only in left lower
extremity at 120º/s angular velocity.
One may ask why before and after the experiment
there were no significant differences in the level of dynamic strength of right and left lower extremity extensors
(at 60º/s and 120º/s, and 60º/s angular velocity, respectively). Perhaps motor activities in the regular basketball
training resulted in the development of high strength
level of knee extensors, and the experiment was not
Table 3. Descriptive statistics and significance level of the differences in vertical jump [cm]
N
x± S
min – max
Sk
Ku
I
18
40,2 ± 4,86
30,9 – 52,1
0,494
1,050
II
18
40,0 ± 4,30
32,3 – 47,7
–0,350
–0,525
I
18
40,2 ± 4,86
30,9 – 52,1
0,494
1,050
III*
18
39,7 ± 4,44
32,4 – 47,4
–0,152
–1,122
II
18
40,0 ± 4,30
32,3 – 47,7
–0,350
–0,525
III*
18
39,7 ± 4,44
32,4 – 47,4
–0,152
–1,122
T
p
0,235
0,817
0,992
0,335
1,022
0,321
-
-
-
-
-
Test
* Having observed no statistically significant changes in the level of explosive leg and trunk strength, the researchers decided to carry out test III believing
that a longer rest period will allow the subjects to show the real level of the tested ability.
– 37 –
Table 4. Descriptive statistics and significance level of the differences for the right lower extremity flexor muscles [Nm]
Test
Angular
velocity
I
60 deg/s
x± S
min – max
Sk
Ku
171,8 ± 49,53
93,8 – 303,0
1,304
2,631
197,3 ± 55,06
125,0 – 322,0
1,298
1,059
158,8 ± 36,82
79,4 – 243,0
0,533
2,205
177,6 ± 44,03
120,0 – 279,0
1,304
1,270
127,1 ± 23,97
90,7 – 175,0
0,841
0,045
145,2 ± 28,79
99,6 – 204,0
0,631
–0,009
N
18
II
60 deg/s
I
120 deg/s
18
II
120 deg/s
I
240 deg/s
18
II
240 deg/s
a sufficient stimulus to bring about the intended effects.
Statistically significant differences between the values of
muscle torque of flexors (6 cases) and extensors (3 cases) may suggest that in basketball training insufficient attention was devoted to the muscles responsible for knee
flexion, which confirms their susceptibility to the stimulus
of the plyometric training (Table 4–7).
According to Wilkerson et al. [11] the value of conventional knee flexors/extensors ratio should be equal
to 2:3. However, varied values of this ratio (Hamstring/
Quadriceps) have been reported in scientific research,
depending on the tested velocity, the subject’s position,
the test muscle group [27, 28]. Nevertheless, many
authors accept 0.6 as the normative value of the knee
conventional ratio at 60°/s angular velocity; it increases
to 0.8 at higher velocities of the isokinetic assessment
[29–31].
It should be noted that before the experiment most
of the subjects had a correct conventional ratio of knee
T
p
–4,610
0,000
–3,984
0,001
–5,698
0,000
extensor and flexor muscles (Hcon/Qcon) (Table 8),
and the statistically significant changes caused by
the plyometric training occurred only in the lower right
extremity. It might be said that the plyometric training
to a greater extent affected the weaker muscle group,
that is hamstrings (semimembranosus muscle, semitendinosus muscle, biceps femoris muscle), causing
compensation changes. Changes leading towards
the proper muscle ratio were particularly visible in the
lower extremity, which – as it was already mentioned
above – performs particular work during training and
game. After the experiment the results of the described
ratio of right lower extremity exceeded the normative
values at 240º/s angular velocity, mostly due to the
large increase of the flexors’ strength endurance level.
It should be remembered that before the experiment
the right lower extremity demonstrated correct values
of conventional knee flexors/extensors ratio (60°/s – 0.
63, 120°/s – 0.76, 240°/s – 0.86). After the experiment
Table 5. Descriptive statistics and significance level of the differences for the left lower extremity flexor muscles [Nm]
Angular velocity
N
60 deg/s
x± S
min – max
Sk
Ku
172,57 ± 43,39
129,0 – 272,0
1,516
1,700
187,50 ± 43,52
139,0 – 290,0
1,288
1,039
157,25 ± 30,21
114,0 – 218,0
0,855
0,366
169,00 ± 32,93
136,0 – 234,0
1,133
0,084
123,09 ± 20,13
93,5 – 157,0
0,108
–0,983
134,00 ± 16,12
107,0 – 161,0
0,168
–0,945
18
p
–4,151
0,000
–2,964
0,009
–2,971
0,009
-
60 deg/s
T
120 deg/s
-
18
-
120 deg/s
240 deg/s
18
-
-
240 deg/s
– 38 –
Table 6. Descriptive statistics and significance level of the differences for the left lower extremity extensor muscles [Nm]
Test
Angular
velocity
I
60 deg/s
II
60 deg/s
I
120 deg/s
II
120 deg/s
I
240 deg/s
II
240 deg/s
N
18
18
18
x± S
min – max
Sk
Ku
259,56 ± 62,41
162,0 – 416,0
1,001
1,650
267,06 ± 60,41
178,0 – 411,0
0,948
1,034
211,25 ± 39,50
160,0 – 317,0
1,499
2,526
223,44 ± 43,87
172,0 – 319,0
0,937
0,341
150,56 ± 26,45
105,0 – 187,0
–0,080
–1,140
164,94 ± 23,54
126,0 – 218,0
0,518
0,495
this ratio was incorrect and at 240º/s angular velocity it
exceeded normative data (0.98) (Table 8).
Out of 40 parameters describing speed and speed
endurance, its derivative, statistically significant changes
were observed in the values before and after the experiment in 19 cases in the experiment group; no such changes were recorded in the control group (Table 9–12, Figure
1 and 2). It should also be noted that what improved was
endurance abilities, not speed abilities, as could be suggested by the type of the training experiment. All significant differences in the running test were only noticed in
the 6th or 7th repetition (when the subjects had already
run 5 × 30m). The differences were not recorded in any
of the first runs at 5 m, 10 m, 20 m or 30 m distance,
which confirms the above mentioned observation on the
endurance type of changes in motor abilities of basketball players. According to Wachowski et al. [13] there was
no correlation between the running speed and the power
and strength tests. The obtained results show that there is
a small relation (too many components) between running
speed and strength and power. Therefore, it should not
be assumed that a plyometric training focused on power
development will result in better results in running tests.
T
p
–1,205
0,246
–2,674
0,017
–3,560
0,002
Moreover, the authors claim that in optimal conditions for
strength and power development, running speed level depends on the running technique (the length and frequency
of step).
Changes in motor abilities in the experiment group
resulted from the plyometric training structure, as well
as from the subjects susceptibility to training impulses
(sensitive periods). Thus the research question should be
considered from two perspectives; that is, from the educational and ontogenetic perspective.
Literature analysis [5, 13, 14, 17, 32–36] allows for
a conclusion that the slowest is the annual speed increase (5%) which grows best up to age 16. Faster development can be observed in the case of jumping abilities
(7%) and power (6%), and the sensitive period for these
abilities occurs at age 13–15.
The development of jumping abilities is mainly related to the training of the capability of fast and economic
use of muscle strength (neuromuscular coordination)
of lower extremities. It depends, among others, on the
elastic elements acting within the ankle joint. It can thus
be said that the experiment was too short to cause any
significant changes in the level of relative strength,
Table 7. Descriptive statistics and significance level of the differences for the right lower extremity extensor muscles [Nm]
Test
Angular
velocity
I
60 deg/s
N
x± S
min – max
Sk
Ku
261,56 ± 54,69
187,0 – 400,0
1,105
1,483
268,81 ± 64,72
181,0 – 412,0
0,948
0,224
209,81 ± 49,46
145,0 – 333,0
1,324
1,312
218,37 ± 47,48
154,0 – 327,0
0,971
0,589
141,81 ± 26,28
101,0 – 202,0
0,705
0,363
152,69 ± 23,64
116,0 – 194,0
0,434
–0,700
II
60 deg/s
I
120 deg/s
18
-
-
-
18
II
120 deg/s
I
240 deg/s
18
240 deg/s
-
-
II
– 39 –
T
p
–0,978
0,343
–1,593
0,131
–2,193
0,044
Table 8. Descriptive statistics and significance level of the differences for conventional knee flexors/extensors ratio
Angular
velocity
Conventional index
x± S
min – max
Sk
Ku
T
p
47,5
0,289
67,5
0,979
62,0
0,756
9,0
0,006
25,0
0,084
27,5
0,036
Left lower extremity
60 I
0,68
0,68 ± 0,10
0,50 – 0,91
0,495
0,507
60 II
0,70
0,70 ± 0,07
0,60 – 0,84
0,355
–0,532
120 I
0,76
0,76 ± 0,08
0,59 – 0,9
–0,161
–0,345
120 II
0,76
0,76 ± 0,08
0,62 – 0,92
0,195
–0,670
240 I
0,86
0,86 ± 0,16
0,61 – 1,25
0,791
0,994
240 II
0,87
0,87 ± 0,13
0,64 – 1,14
0,254
0,040
-
-
-
-
-
Right lower extremity
60 I
0,63
0,63 ± 0,07
0,48 – 0,74
–0,772
0,131
60 II
0,70
0,70 ± 0,10
0,51 – 0,94
0,262
0,755
120 I
0,76
0,76 ± 0,09
0,55 – 0,89
–0,699
0,650
120 II
0,81
0,81 ± 0,11
0,66 – 1,05
0,696
–0,142
240 I
0,86
0,86 ± 0,21
0,21 – 1,21
–1,867
6,068
240 II
0,98
0,98 ± 0,17
0,61 – 1,19
–0,733
–0,004
responsible for the elevation of the body mass center
during a vertical jump on a platform. It also seems that
boys aged 11–14 are more capable of perfecting their
strength-speed abilities [17].
As a result of the exercises the greatest annual
changes can be observed in endurance and absolute
power training (more than 20%) [33, 17]. It can be expected that the time of the experiment and training load
allowed only for the development of endurance changes in running tests (Table 9–12, Figure 1 and 2). Such
interpretation of the results is confirmed by the high
level of running endurance and strength endurance of
knee flexors and extensors. Significant changes in the
muscle torque values in tests performed on the isokinetic dynamometer at 240º/s angular velocity characterize changes in strength endurance, while the value
of muscle torque at 60º/s angular velocity suggests
changes of dynamic strength.
Basketball players from the experiment group performed more than 3000 jumps during the proper phase
of the experiment (I and II). That is a lot, taking into consideration the time span of the experiment: eight weeks
(Table 2). One may ask whether three days of rest were
enough for four days of plyometric training. To com-
pare with other research, in a study by Kubaszczyk and
Litkowycz [10] basketball players were subject to a plyometric training twice a week for five months, performing
approximately 2500 jumps. As a result, there were significant changes in the dynamic strength level measured
by a vertical jump, long jump from a spot and triple jump.
It should be noted that in spite of the fact that the training load was divided into five months, during the second
measurement (out of three), in the middle of the experiment, the authors recorded a regress of results. What
occurred was a common phenomenon observed in all
tests: a decrease in the level of strength-speed abilities
value, after which a significant improvement occurred,
with values higher than those before the experiment.
After the fatigue accumulation effect, supercompensation occurred. It can thus be said that prolonging the
experiment at the expense of one training unit would
allow for achieving satisfactory results not only in the
level of endurance abilities but, above all, of speed abilities. Another reason for significant differences in the
level of dynamic strength of lower extremities in basketball players tested by Kubaszczyk and Litkowycz [10]
is the age of subjects (16 years) and thus their greater
susceptibility to strength-speed training impulse.
– 40 –
-
-
-
-
-
Table 9. Descriptive statistics and significance level of the differences for 5m run [s]
Test
Run
N
x± S
min – max
Sk
Ku
I
1
188
1,34 ± 0,07
1,18 – 1,48
–0,404
0,572
II
1
18
1,27 ± 0,04
1,20 – 1,35
0,112
0,014
I
2
18
1,35 ± 0,10
1,17 – 1,55
–0,029
–0,411
II
2
18
1,30 ± 0,05
1,21 – 1,38
–0,295
–0,296
I
3
18
1,35 ± 0,09
1,16 – 1,51
–0,282
–0,523
II
3
18
1,30 ± 0,05
1,24 – 1,40
1,142
0,331
I
4
18
1,37 ± 0,08
1,24 – 1,49
0,113
–1,456
II
4
18
1,30 ± 0,05
1,22 – 1,40
–0,019
–0,482
I
5
18
1,38 ± 0,10
1,19 – 1,58
–0,245
–0,371
II
5
18
1,33 ± 0,04
1,23 – 1,39
–0,927
0,835
I
6
18
1,39 ± 0,07
1,29 – 1,58
1,091
1,507
II
6
18
1,31 ± 0,07
1,15 – 1,38
–1,389
2,091
I
7
18
1,39 ± 0,07
1,25 – 1,57
0,428
0,988
II
7
18
1,31 ± 0,04
1,27 – 1,39
1,318
0,924
I
8
18
1,41 ± 0,08
1,28 – 1,63
0,732
1,628
II
8
18
1,32 ± 0,02
1,30 – 1,36
0,360
–1,474
I
9
18
1,42 ± 0,08
1,23 – 1,55
–0,698
1,047
II
9
18
1,32 ± 0,05
1,26 – 1,41
0,421
–0,507
I
10
18
1,42 ± 0,08
1,32 – 1,60
0,772
–0,081
II
10
18
1,31 ± 0,06
1,25 – 1,42
1,066
0,014
Cossor et al. [22] described the effect of 20 weeks
of plyometric training. During the study subjects (12–16
year old swimmers) performed a total of 2700 jumps.
After the experiment there were no significant changes
in the values of explosive leg strength in the young
swimmers. The authors suggest two most probable reasons for such a situation: first, physical load imposed by
the plyometric training turned out to be too low, as the
authors used load recommended for training children.
Out of the two components of training load, the body
of a young athlete better tolerates volume better than
intensity. The second reason is the young swimmers’
growth process.
Authors [12, 15, 18–21, 37] of some research papers have not observed any significant increase of
sport achievements after applying the plyometric train-
T
p
11,5
0,055
31,5
0,893
25,0
0,798
11,5
0,055
27,0
0,593
11,5
0,055
2,0
0,005
12,5
0,068
6,5
0,018
5,0
0,021
ing, which was most probably due to a too short plyometric program. Burr and Young [20] believe that the
plyometric training should be carried out for at least 18
weeks for the positive effects to appear. High intensity
exercises which affect the nervous system should only
be applied in individuals where the growth process is
completed. Particular plyometric exercises should be
performed with maximum strength (when the subject
is not fatigued), and rest periods should take at least as
much time as the exercises.
The conclusions concerning the application of
plyometric exercises in a training process can be now
formed. Basketball training should be supported by plyometric training, and its intensity, one of the components
of load, should exceed average values appropriate to
the subject’s age. Increasing the training volume and
– 41 –
x ± S
min – max
Sk
Ku
188
2,81 ± 0,11
2,59 – 3,00
–0,208
–0,123
18
2,71 ± 0,08
2,61 – 2,89
0,952
1,103
2
18
2,84 ± 0,16
2,56 – 3,14
0,097
–0,461
II
2
18
2,76 ± 0,08
2,66 – 2,91
0,585
–0,972
I
3
18
2,87 ± 0,15
2,61 – 3,15
0,197
–0,717
II
3
18
2,78 ± 0,10
2,64 – 2,99
0,877
0,603
I
4
18
2,90 ± 0,14
2,71 – 3,23
0,801
–0,177
II
4
18
2,79 ± 0,09
2,64– 3,95
0,529
–0,016
I
5
18
2,91 ± 0,16
2,64 – 3,23
–0,021
–0,484
II
5
18
2,81 ± 0,09
2,65 – 2,95
0,074
0,360
I
6
18
2,93 ± 0,13
2,77 – 3,22
0,908
0,570
II
6
18
2,79 ± 0,09
2,64 – 2,92
–0,302
–0,640
I
7
18
2,94 ± 0,13
2,69 – 3,22
0,436
0,065
II
7
18
2,79 ± 0,10
2,70 – 3,03
1,745
2,267
I
8
18
2,97 ± 0,15
2,76 – 3,34
0,844
0,993
II
8
18
2,81 ± 0,07
2,72 – 2,96
0,874
0,834
Test
Run
N
I
1
II
1
I
I
9
18
2,98 ± 0,12
2,70 – 3,18
–0,511
0,502
II
9
18
2,82 ± 0,09
2,72 – 3,04
1,399
2,519
I
10
18
2,98 ± 0,15
2,77 – 3,33
0,765
0,225
II
10
18
2,80 ± 0,12
2,69 – 3,06
1,322
1,056
T
p
9,5
0,066
30,5
0,824
21,0
0,858
9,5
0,066
19,0
0,386
5,0
0,012
4,5
0,011
2,0
0,009
5,0
0,012
3,0
0,007
T
p
10,5
0,083
30,5
0,824
31,0
0,858
10,0
0,040
17,5
0,308
6,0
0,016
5,0
0,012
6,0
0,016
4,5
0,011
3,0
0,007
Table 11. Descriptive statistics and significance level of the differences for 20m run m [s]
Test
Run
N
x± S
min – max
Sk
Ku
I
1
188
3,47 ± 0,14
3,21 – 3,70
–0,260
–0,555
II
1
18
3,36 ± 0,10
3,23– 3,58
0,929
1,046
I
2
18
3,51 ± 0,19
3,19 – 3,86
0,171
–0,587
II
2
18
3,42 ± 0,10
3,32 – 3,61
0,778
–0,819
I
3
18
3,55 ± 0,18
3,26 – 3,91
0,355
–0,622
II
3
18
3,45 ± 0,12
3,27 – 3,70
0,709
0,076
I
4
18
3,59 ± 0,18
3,37 – 4,04
0,926
0,338
II
4
18
3,46 ± 0,12
3,27 – 3,66
0,616
0,307
I
5
18
3,60 ± 0,19
3,28 – 4,01
0,119
–0,534
II
5
18
3,48 ± 0,11
3,27 – 3,67
0,295
0,836
6
18
3,62 ± 0,17
3,42 – 4,03
0,874
0,424
6
18
3,46 ± 0,10
3,31 – 3,62
0,215
–0,373
I
7
18
3,63 ± 0,17
3,35 – 3,99
0,519
–0,195
II
7
18
3,46 ± 0,13
3,36 – 3,79
1,867
2,948
I
8
18
3,67 ± 0,18
3,43 – 4,07
0,801
0,518
II
8
18
3,48 ± 0,10
3,35 – 3,71
1,147
1,724
I
9
18
3,68 ± 0,14
3,36 – 3,93
–0,258
0,102
II
9
18
3,49 ± 0,11
3,36 – 3,76
1,534
2,784
I
10
18
3,69 ± 0,19
3,41 – 4,15
0,780
0,333
II
10
18
3,48 ± 0,15
3,34 – 3,82
1,542
1,717
-
-
-
-
-
I
II
– 42 –
Run
N
x±S
min – max
Sk
Ku
I
1
18
4,79 ± 0,20
4,48 – 5,16
0,278
–0,947
II
1
18
4,64 ± 0,15
4,45 – 4,98
1,086
1,530
I
2
18
4,85 ± 0,25
4,43 – 5,36
0,285
–0,655
II
2
18
4,71 ± 0,15
4,56 – 5,00
0,917
–0,362
I
3
18
4,92 ± 0,26
4,56 – 5,47
0,539
–0,610
II
3
18
4,77 ± 0,18
4,53 – 5,11
0,708
–0,366
I
4
18
4,99 ± 0,29
4,67 – 5,73
1,089
0,909
II
4
18
4,78 ± 0,17
4,55 – 5,10
0,927
0,457
I
5
18
4,99 ± 0,28
4,57 – 5,51
0,185
–0,908
II
5
18
4,80 ± 0,16
4,54 – 5,09
0,808
0,771
I
6
18
5,02 ± 0,26
4,70 – 5,67
0,949
0,481
II
6
18
4,79 ± 0,14
4,61 – 5,08
0,918
0,524
I
7
18
5,03 ± 0,25
4,65 – 5,57
0,614
–0,424
II
7
18
4,79 ± 0,20
4,62 – 5,28
1,945
3,402
I
8
18
5,09 ± 0,24
4,74 – 5,67
0,823
0,583
II
8
18
4,82 ± 0,15
4,65 – 5,17
1,434
1,867
I
9
18
5,10 ± 0,22
4,65 – 5,48
0,011
–0,225
II
9
18
4,82 ± 0,17
4,61 – 5,23
1,614
3,131
I
10
18
5,13 ± 0,30
4,67 – 5,77
0,699
0,275
II
10
18
4,80 ± 0,21
4,62 – 5,31
1,685
2,410
reducing rest periods will adversely affect the release
of elastic energy during exercises and decrease the explosive strength level. Prolonging the transition phase
(stance phase) leads to the diffusion of elastic energy
accumulated in tissues into chemical energy and heat
[8]. Duda [38] claims that if we shorten ground contact
time during take-off, jump height will increase; an identical mechanism is performed in specific plyometric exercises. Future research including the plyometric training should consider the intensification of youth training
by exercises that do not burden the motor system, that
is the so-called ‘hexagon’: skipping rope, jumps over
a line, depth jumps from low heights (e.g. from a bench,
not higher) stressing the short stance phase with jump
up and short acceleration phase. In mature athletes
similar exercises should be used, increasing the height
of accessories (vaulting boxes, hurdles), adding medicine balls – enforcing short ground contact time after
landing.
-
T
p
15,0
0,109
26,5
0,563
29,5
0,755
12,5
0,068
17,0
0,154
2,0
0,009
5,0
0,012
2,0
0,005
3,0
0,007
1,0
0,004
The research results and the discussion presented
above allow us to present the following conclusions:
1. Plyometric training increases knee flexor and extensor
muscle strength, but its effects are greater in the case of
weaker muscles – hamstrings (semimembranosus muscle, semitendinosus muscle, biceps femoris muscle).
2. Weekly plyometric training load turned out to be too
much (mainly due to the volume component), causes
endurance changes in general physical ability of the
subjects.
3. Changes in knee flexor and extensor muscles in
basketball players ought to be considered in the aspect of lateralization.
4. Significant changes in the dynamic strength level can
result from plyometric training applied twice a week for
no less than 20 weeks.
5. Plyometric training should include highly intensive exercises; however training methods should be different in
athletes whose growth process is not yet completed.
-
-
Test
– 43 –
-
-
-
-
-
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