REASON
The primary objective of this study was to show the effect of 2 years of periodized
strength training on change of direction performance. This study relates to this course for the
inclusion of strength training effects on change of direction, which is a part of speed and agility.
Without effective change of direction in sport, we are limited in our athletic performance and
productibility of a positive outcome.
INTRODUCTION
There is a different requirement profile for each individual sport and strength and speed
are important for the performance in each sport. Strength and speed will determine the outcome
of the game, thus, sprinting is a performance limiting factor in sports. Alongside linear sprinting,
change of direction sprinting(COD) must be performed in sports. COD is measured using agility
tests, however, these agility tests do not reflect the demands of these respective sports. This study
aims to clarify if there is a strength training effect on sprint time and to analyze correlations
between 1RM squats (front and back) and the COD.
METHODS
The study used 112 elite youth soccer players and divided into 2 groups. 36 professional
soccer players were also selected as a performance standard for the youth soccer players. One
group performed a periodized training plan alongside their regular soccer training (STG) while
the other group did only soccer training (CG). The STG incorporated strength training twice per
week with soccer sessions 3-4 times per week. CG had solely soccer training 3-4 times per week.
Each group then formed subgroups based on age. These subgroups broke down into the ages of
19, 17, and 15 years old. All participants were familiarized with the tests by performing a pretest
1 week prior to testing. No subject participated in any fatiguing sessions at least 2 days prior to
testing or reported an injury at the time of testing.
During each of the training sessions, both front and back squats were completed as well
as bench press, deadlifts, neck presses, and exercises for the trunk muscles and the standing row.
The training protocol emphasized correct squat technique during the first 4 weeks. The following
8 weeks, the program emphasized hypertrophy with 5 sets of 10 repetitions with a 3-minute rest
in between sets. The third training block consisted of 5 sets of 6 repetitions with a 3-minute rest.
The final training block consisted of 5 sets of 4 repetitions with a 5-minute rest. The weight
during training sessions was determined by individual ability and correct technique. The weight
would increase if the participant could lift the weight with proper technique. Each training
sessions consisted of a squat variant, 3 upper extremity exercises, and 1 trunk exercise.
The change of direction (COD) performance was measured with double light barriers.
The COD was designed as an equilateral triangle. The participant would start on one side, sprint
to the corner of the triangle and sprinted 2.5m, then performed a change of direction, sprinted 5m
with a second change of direction, then finished with a 2.5m sprint through the final light barrier.
This test was chosen because traditional tests such as the T-test and the Illinois test do not
differentiate between other parameters. The test was used to differentiated changes of direction
and to focus the change of direction using short sprint tracks. Participants completed a 10-minute
warm up prior to testing.
A 1 rep max was also used for front and back squat to determine maximum strength of
lower extremities. The warm-up consisted of 2 sets with 6-8 repetitions with a submaximal
weight. Maximum strength of the front squat was evaluated first, then the back squat.
C cohort is 15 years of age, B cohort is 17 years of age, and A cohort is 19 years of age.
I think a strength of the methods section was the size and age range from the youth soccer
players. There will be large amounts of strength gains, neuromuscularly, based on the population
used.
A negative would be the way of testing for the 1RM front and back squat on the same
day. This could limit the strength because of fatigue from the previous testing. There could also
be a different method of measurement such as a velocity based training apparatus. This could
mitigate injury in the testing process based on protocols for 1RM.
RESULTS
The C cohort revealed no significant differences in all parameters of the COD. The STG
reported T1 times of 1.858 seconds in L5, 1.846 in R5, and 3.501 seconds to 3.481 seconds in
L10 and R10. The CG achieved times of 1.860 in L5, 1.852 in R5, and end times of 3.496 in L10
and 3.453 in R10. In T2, of A-cohort showed no significant differences in the control group
compared against the PRO group. However, the STG in all parameters showed significantly
faster times than the PRO. In B-cohort, PRO showed significantly faster times in L10 and R10
than the control group did. The STG showed no significant differences in the B-cohort compared
to the PRO. In the C-cohort, there was a significant difference between the PRO and control
group at all levels of the COD variables.
DISCUSSION
This study found that additional strength training has a positive effect on the performance
in the COD and maximum strength in the front and back squats relative to body weight. The
study also found that moderate to high significant correlations exist between the relative
maximum strength and the parameters of the COD. Previous studies report shorter intervention
periods of 8-15 weeks and strength training protocols lasting longer than a year in youth soccer
were not found.
During this study, it is possible that both strength gains and neuromuscular gains were
achieved. The CNS must learn to transfer the performance of the neuromuscular system in a task.
The harder the task, the lower the chance of transfer. The longer the individual is training, the
more likely the increased strength is transferred to the target movement.
Additionally, gains in deceleration can have an effect on shorter sprint times in COD. It is
possible that the higher the maximum strength level, the faster the COD times and deceleration.
Since the slower times in COD cohorts A and B cannot be explained, is it assumed the cause is
developmental in nature. Maybe the increases of strength gains do not mimic the developmental
changes and compromised coordination.
A strength from their discussion was the effect sizes and the favorable data to show the
effectiveness of strength training on change of direction performance.
A negative would be the programming lacking a day and the inclusion of unilateral work
alongside squatting. This could have elicited a higher strength response with the possible
inclusion of plyometrics to help with target movements.
CONCLUSION
Long term strength training is appropriate to improve COD performance for all athletes.
The additional periodized strength training programs are recommended for all sports where COD
could be a limiting factor. Youth athletes starting as young as 6 or 7 can benefit from these
interventions. Those athletes will have an advantage from the long term strength training.
References
Carr, J. C., Ye, X., Wages, N., & Bemben, M. (2018). Unilateral Strength Training Changes
Direction Of Strength Asymmetry But Not Magnitude In Healthy Individuals. Medicine
& Science in Sports & Exercise, 50, 417–418.
https://doi.org/10.1249/01.mss.0000536461.51485.10
Hammami, M., Gaamouri, N., Cherni, Y., Chelly, M. S., Hill, L., & Knechtle, B. (2021). Effects
of contrast strength training with elastic band program on sprint, jump, strength, balance
and repeated change of direction in young female handball players. International Journal
of Sports Science & Coaching, 174795412110507.
https://doi.org/10.1177/17479541211050724
Keller, S., Koob, A., Corak, D., von Schöning, V., & Born, D.-P. (2018). How to Improve
Change-of-Direction Speed in Junior Team Sport Athletes—Horizontal, Vertical,
Maximal, or Explosive Strength Training? Journal of Strength and Conditioning
Research, 1. https://doi.org/10.1519/jsc.0000000000002814
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