Clinical Trial Details
— Status: Withdrawn
Administrative data
| NCT number |
NCT04738617 |
| Other study ID # |
CEFADE 03 2021 |
| Secondary ID |
|
| Status |
Withdrawn |
| Phase |
N/A
|
| First received |
|
| Last updated |
|
| Start date |
January 1, 2023 |
| Est. completion date |
September 1, 2023 |
Study information
| Verified date |
May 2023 |
| Source |
Universidade do Porto |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Interventional
|
Clinical Trial Summary
The goal is to assess inter- and intraindividual variation in response to different warm-up
protocols in a randomized, cross-over study with U16 and U17 Portuguese soccer players.
Description:
Trial design We are following the Consolidated Standards of Reporting Trials (CONSORT) 2010
statement: extension to randomized crossover trials (Dwan, Li, Altman, & Elbourne, 2019).
Randomized crossover designs increasing statistical power, as participants act as their own
controls (Dwan et al., 2019). Here, a randomized crossover design with two arms is
elaborated. A two-week familiarization period with the two interventions and with testing
will be performed, during which the participants will make four visits, in all of which they
will go through pre-testing, protocols A and B (on alternate days), followed by post-testing.
This period will be followed by two-weeks of performing each intervention, separated by a
two-week wash-out period to avoid a carryover effect (Higgins et al., 2019), which is
superior to that used in similar research (Barbosa et al., 2019). In each period, the groups
will perform four visits in terms of intervention, and in two of those visits they will be
tested with the goal of assessing within-group, within-intervention consistency. Allocation
ratio will be ~1:1. The protocol will be sent to approved by the Ethics Committee of the
Faculty of Sport of the University Porto, and then registered at
http://www.clinicaltrials.gov. Participants will be informed of the goals and methods of the
research and their legal tutors will sign informed consent forms (as they will be <18
years-old), following the updated version (2013) of the Declaration of Helsinki.
Participants Participants will be 40 to 50 healthy football players from the U16 and U17
teams of a club from the Oporto city, engaged in three weekly training sessions with an
average weekly training volume of 270 minutes. Following similar research (Beato, De Keijzer,
et al., 2019), participants will have to be free from injuries or illness at the start of the
study. Data will be collected in the facilities of the club where the participants play, and
therefore no familiarization to the environment will be required.
Interventions In line with previous research (Beato, De Keijzer, et al., 2019; Faude, Roth,
Di Giovine, Zahner, & Donath, 2013), a 10-minute general warm-up will precede the
implementation of the specific warm-up protocols. The general warm-up will consist of three
minutes running at low to moderated intensity, followed by three minutes of active, dynamic
mobility work, followed by approximately four minutes of 20-m accelerations at 70% of maximum
perceived intensity, where each player will perform 5 repetitions of increasing distances
(i.e., 10 m, 15 m, 20 m, 25 m, 30 m). During the pre-tests, general warm-up, interventions
and post-tests, players will wear Global Positioning System (GPS, VX Sport, Model VXLOG 175).
The interventions will consist of two different warm-up strategies. In the first two weeks of
implementation, one group will perform intervention A while the other will perform
intervention B. After the wash-out period, the groups will crossover (AB/BA design). In each
two-week period of the interventions, the participants will make two weekly visits, in a
total of four visits per period. In the first visit of each week, the participants will only
perform the interventions, while in the second visit of each week, the participants will also
engage in pre- and post-testing. Therefore, two tests per period will be applied.
Intervention A is based on football-specific small-sided games (SSGs), consisting of 4 versus
4 matches (with mini-goals), performed in a 30 m by 24 m court (Giménez et al., 2018), using
five sets of 90 seconds of work interspersed with 30 seconds of pause, in a total duration of
10 minutes. Intervention B is based on speed, COD and plyometrics (i.e., a "potentiation"
protocol), inspired by ideas presented by Howe, Coward, and Price (2017). Participants will
perform five repetitions of the following exercises, in this order: unilateral hurdle hops
and lateral hurdle hops with each lower limb; countermovement jump; broad jump; forward in
and out; slalom jumps; lateral scissor jumps; single leg linear hops. Each intervention will
last ~10 minutes and will be applied in the football field. Two experienced football coaches
with a degree in Sports Sciences will deliver and monitor all the sessions. The interventions
were designed to be easily applicable by coaches without the need for sophisticated
facilities or material. All interventions will be implemented at the same time of the day and
in the same days of the week for both groups. Due to the nature of the interventions,
participants and implementers will not be blinded.
Sample size The software G*Power (version 3.1.9.6. for Mac) was used to assess a priori
sample power. Considering a repeated-measures ANOVA, for within factors, with a power of
0.95, α = 0.05, correlation coefficient of 0.5, non-sphericity correction of 1, effect size
of 0.35, two groups and four measures (i.e., outcomes), minimum sample size was established
in 20 subjects. For also analyzing within-between interactions, 36 subjects were required,
which is still below our estimated sample of 40-50 participants.
Randomization In this crossover study, some athletes will perform an AB sequence, while
others will perform a BA sequence. It is predetermined that each group will have ~50% of the
participants, without any further rules being stipulated for randomization. Randomization
will be performed only after the two-week familiarization periods and the pre-tests. The
random allocation sequence will be performed by a researcher not involved in testing or in
monitoring the interventions. Two opaque bags will be used: (i) the first bag containing
folded papers with the names of the participants; (ii) the second bag containing the
intervention (i.e., A or B). In each round, the researcher will remove a paper from the
second bag, followed by a paper from the first bag. Allocation will be concealed from all
other researchers until the start of the intervention. The two main testers will not be
provided with this information, to ensure they remain blinded. If allocation suggests
problems with baseline values, creating imbalances in the groups with respect to the values
obtained in the four tests, the randomization process will be repeated.
