Effects of a Tapering Period on Physical Condition in Soccer Players

3 4 The aim of this research was to analyze the effects of a two-week step tapering 5 period on lower-limb muscle power, change of direction (COD) and acceleration 6 capacities, and on the stress-recovery state in an amateur soccer team. Twenty-two 7 male players were included in the study. Following a six-week progressive 8 training, the sample was divided into: experimental group (n = 11), who did a 9 two-week period of taper in which training volume was 50% reduced (intensity 10 was kept high) and control group (n = 11), which kept on with the training. 11 Muscle power (countermovement jump test), acceleration (10m sprint test), COD 12 (Illinois test) and stress and recovery perceptions (RESTQ questionnaire) were 13 evaluated before training, at the end of it (pre-tapering, PRE-TP) and after the 14 tapering period (post-tapering, POST-TP). Following the taper, the experimental 15 group in comparison to the control group showed significantly improved power 16 (1029.71 ± 108.51 W/kg vs. 1084.21 ± 110.87 W/kg; p < 0.01), acceleration (1.72 17 ± 0.09 s vs. 1.67 ± 0.07 s; p < 0.05), and lower stress levels (1.9±0.5 vs. 1.6±0.5; p 18 < 0.01) (PRE-TP vs. POST-TP, respectively). COD did not show significant 19 changes. In conclusion, a two-week step tapering program was found to be an 20 effective periodization strategy to increase muscle power and acceleration, and to 21 reduce stress perception in soccer amateur players.


INTRODUCTION
Soccer is a high-intensity intermittent and multi-component sport in which performance relies not only on individual factors such as physical fitness or technical skills but also on the interaction among the players within the team for optimal tactical strategies (31).The game involves multiple motor skills and running is the predominant one, yet explosive type efforts such as sprints, jumps, dribbling, kicking, are also important for successful performance (2).These quick efforts depend on optimal physical capabilities, among which lower limb anaerobic power is particularly important (9,27).
Soccer League championships are characterized by a long competitive season with frequent matches and training sessions that could induce chronic fatigue on the players (34).Due to this fact, a balance between training stimulus and physical recovery is fundamental to optimize physiological adaptations and physical performance while avoiding excessive fatigue (24).In order to achieve this goal, progressive planning of the training load around the competitive phases and its continuous monitoring are relevant procedures (36).High training loads with insufficient periodization of recovery periods has been suggested to cause overreaching and overtraining in team sport players such as soccer (22).In an attempt to maximize performance after an intense training period, a short-term reduction of training load at the end of a mesocycle has been found beneficial to avoid excessive physiological and psychological stress (5).This periodization

A C C E P T E D
Copyright ª 2017 National Strength and Conditioning Association strategy, known as "tapering", is characterized by reducing the volume and/or frequency of training while intensity is maintained (5).
The improvements in physical condition and performance following a tapering period have been mostly studied in individual sports, with less research performed in team sports (5).Research done in semi-professional male rugby players (10), elite female basketball players (28), young male (16) and elite soccer players (14) support the benefits of tapering on team sports performance, too.
However, there is still a paucity of information on the effectiveness of manipulating training load on specific physical condition components such as anaerobic muscle power and related components such as change of direction (COD), which are relevant to reach optimal fitness level in soccer players (29).
A better understanding of the training stimulus and adaptations occurring during progressive loading and tapering periods may improve training load prescription and periodization for soccer players.Therefore, the aim of this research was to examine the effect of a two-week step taper period on physical condition characteristics such as muscle power, COD and acceleration in an amateur soccer team.In addition, we evaluated the effect of decreasing training load (TL) during taper weeks on subjective stress and recovery perceptions.

Subjects
Twenty-two male amateur soccer players from the same team volunteered to take part in the study (age: 23 ± 5 years; body mass: 74.5 ± 7 kg; height: 1.77 ± 5 m; experience as federated players: 11 ± 5 years).All participants were informed of the benefits and risks of the investigation and gave written informed consent prior to participation in the study.The research project was approved by the EUSES-TE Institutional Review Board.

Training intervention
Plyometric training sessions were performed twice a week after the warm-up, with 48-72h of rest between them.The design of the plyometric intervention was progressed based on the players' previous training records.Before beginning the training period, players were instructed on how to perform all the exercises.the number of jumps, repetitions or sets.After that, the intensity was increased 5% by augmenting the height of vertical jumps and the distance of horizontal jumps, according to previous height or distance measured for each participant.
Each exercise set of repetitions lasted between 8-12 seconds.A complete recovery between sets was allowed, following a ratio load:recovery of 1:6 (1), so that recovery lasted between 50s and 70s.The order of the tasks was based on exercise complexity, from more to less intense jumps.
Small Sided Games for the sport-specific training were performed in the three training sessions completed per week.In alternate weeks, volume and intensity of the exercises were increased.Volume was modified firstly by increasing the duration of each task or the number of tasks per session performed.Then, intensity was progressed by allowing lower number of ball contacts per player or by decreasing the playing area (30).
A step tapering period lasting 2 weeks was applied to the EG following

Recovery-Stress State
The Spanish version of the Recovery-Stress Questionnaire for Athletes (RESTQ-76) was used to identify the physical and mental stress experienced by the players and their current state of recovery (17).RESTQ-76 is composed by 12 General The best performance was considered for data analyses.

Lower-limb muscle power was evaluated by a countermovement jump (CMJ).
Following a regular 10-minute warm up, the CMJs were performed on a contact mat (ChronoJump-Boscosystem platform) validated by DeBlas (4).Participants started from a standing position with hands on their hips and were instructed to perform a fast-downward movement up to 90° of knee flexion followed by an upward movement trying to jump as high as possible.The trial reporting maximum jump power was selected for further analysis (CMJ ICC = 0.94).
The Illinois COD Test (Figure 1) was set up and administered using according to Hoffman (2006).The test is set up with four cones forming a square for the COD test area (10 m x 5 m).Participants started on the ground in a prone position, with their head just behind the start line and hands shoulder-width apart.On the "Go"

Statistical analyses
The assumption of normality was verified using the Shapiro-Wilk test.The paired sample T-test was used to evaluate changes between pre-training and post-training in all the players.The independent samples T-test was used to examine between group differences in the baseline measurements of interest.The analysis of

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Copyright ª 2017 National Strength and Conditioning Association variance (ANOVA) with two-way repeated measures for time (pre-tapering and post-tapering) and group (experimental and control) was performed to assess the tapering intervention.Whenever a significant group x time interaction was observed, Bonferroni's post hoc correction was used to aid interpretation of these interactions.Cohen's d was calculated to evaluate the effect size (ES) of the intervention within the groups with the following interpretation: small (0.2), medium (0.5) and large (0.8) (8), whilst analyses for between-groups differences were calculated using partial eta-squared (η

RESULTS
Baseline differences were not found between groups for all the variables analyzed.

A C C E P T E D
Copyright ª 2017 National Strength and Conditioning Association Our results are in agreement with previous research reporting improvements in anaerobic performance evaluated by muscle power and acceleration variables in team (10,28) and individual sports (7,39) following a tapering period.The magnitude of the improvements are in line with previous studies evaluating muscle or acceleration capacities (10,28).Despite the fact that a positive effect of tapering on COD has been reported previously (28), our results showed a tendency to improve but it did not reach statistical significance (p = 0.08).This fact could be due to a major dependence of technical and coordinative abilities not influenced by the characteristics of the tapering period applied.
Tapering has been suggested to increase muscle performance by reducing muscle damage (10), increasing neural drive (18) and increasing cross-section area (CSA) in type IIA muscle fibers (39).These adaptations might be obviously related to the type of training performed previously and during tapering.Since muscle power and acceleration are determinant physical capabilities for quick and high-intensity actions over short distances common in soccer (6,26), its optimization before an important competition could positively influence the outcomes.
Accelerations and vertical jumping are common match actions in soccer which are involved in goal scoring, creating space and gaining ball possession (12,13).Power production capacity is one of the most important neuromuscular capacities involved in these soccer explosive abilities and overall performance

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Copyright ª 2017 National Strength and Conditioning Association (3,23).In addition, soccer players with greater muscle power usually experience lower performance decrements in a match (33) and that may also have important consequences on fatigue development and injury risk during games.Therefore, maximizing lower-limb muscle power and running acceleration capacities following a tapering period may positively influence technical and tactical aspects of the match.
We also found out that the perception of stress evaluated by the RESTQ-76 in the experimental group was significantly reduced following the tapering period in comparison to the control group, who felt less recovered at the same time point.This psychological improvement following a tapering period could also influence the enhancement in physical condition reported.Our results are in accordance with previous studies showing reductions in training stress following a tapering period in team sports (11,28).High training load and psychological stress have been related to increased risk of injury and illness in athletes (32,35).
Therefore, monitoring the individual stress-recovery state in athletes could be implemented as a useful prevention tool.
Tapering is not a common practice in soccer; consequently, players could initiate the competitive season with impaired neuromuscular performance due to high volume trainings or reduced recovery (22,38).From a practical point of view, our results support the importance of considering the taper in the periodization of TL and recovery in order to improve fundamental physical capacities for soccer, such as acceleration and power, and to prevent chronic The positive results from our study were obtained following general tapering recommendations made from the meta-analyses of Bosquet et al. (5) who, in terms of duration and variables modification, demonstrated that performance may be maximized with a 2-week tapering period consisting in an exponential reduction of training volume (approximately 41%-60%) without changing training intensity or frequency.However, a step-taper was implemented to accentuate the results due to the short duration of the study (29).Despite other tapering strategies also being helpful to improve soccer performance (14), we think that the approach used in our study is feasible in terms of time planning and appropriate to induce physical adaptations.The inclusion of a control group permitted the isolation of the intervention effects from the general outcomes expected as consequence of the regular training.Nevertheless, the results could be influenced by the fact that control group maintained training load during the tapering period while the experimental group decreased it.
The main limitation of our study was that only physical condition improvements and stress-fatigue parameters were analyzed.Given the complexity of a soccer match, the improvements reported do not guarantee transference to match success after tapering since physical condition is not the only aspect

PRACTICAL APPLICATIONS
The results of our study suggest that tapering can be a useful periodization strategy to be used by coaches in order to achieve players' peak physical        Data presented as mean ± SD and 95% confidence interval in brackets.# Significant interaction group x time from the between-groups analysis.*Significant results within-subject pre/post taper period (p < 0.05).GC: control group; GE: experimental group; PRE-TP: pretapering; POST-TP: post-tapering.η 2 p : partial eta-squared Copyright ª 2017 National Strength and Conditioning Association METHODS Experimental Approach to the Problem The study period was divided into a 6-week mesocycle of progressive training followed by a 2-week tapering period.During the study period, 3 training sessions and one match per week were completed by the players.All the team performed plyometric and COD training, as well as small-sided games during the training sessions.Following the 6-week mesocycle, participants were randomly divided into experimental group (EG), which followed the taper, and control group (CG), which continued with regular training.During the taper, TL was decreased by reducing the duration of each training session.A battery of tests that included muscle power, COD, acceleration and a stress/recovery questionnaire was performed before the progressive training period, at the end of this 6-week training period, which was used as baseline evaluation for the tapering period (pre-tapering, PRE-TP), and at the end of the taper (post-tapering, POST-TP).Internal training load (ITL) was also evaluated after every training session.Participants were well familiarized with the standard technique of each exercise.Copyright ª 2017 National Strength and Conditioning Association Horizontal and vertical jumps (with only left, only right or both legs) were performed with involvement of stretch-shortening cycle muscle activity and immediately after the jumps, a COD drill was performed (changing running direction and starting-stopping quickly).The total number of contacts performed in the first study session was 96 (including 48 foot contacts unilateral and 48 bilateral distributed in 4 sets) and the starting jump height was 60cm for vertical jumps and 120cm for horizontal jumps.Training volume (number of foot contacts) was increased 10% every 3 successive training session by augmenting Copyright ª 2017 National Strength and Conditioning Association

the 6 -
week mesocycle.They continued training at the same intensity but training volume was reduced 50% by lowering time spent in each specific training modality, thus total session duration was reduced.Training frequency was maintained.The CG continued training with the same volume and intensity performed the 6th week of the training mesocycle.Copyright ª 2017 National Strength and Conditioning AssociationMeasurementsInternal Training Load ITL was calculated using the method developed by Foster(15).Briefly, thirtyminutes after completing the training session each athlete provided a rating of perceived exertion (RPE; CR-10 scale) for each session by answering the question: "How was your workout?"The session RPE method has been shown to be a valid method for monitoring training load in soccer players(20).An ITL was calculated by multiplying the session RPE score (indicator of global intensity) by training duration (in minutes).Data from all training sessions were combined to provide an absolute ITL score for each week of training.
Stress and Recovery scales along with 7 Sport-specific Stress and Recovery scales.A Likert-type scale, with values ranging from 0 (never) to 6 (always), indicates how often the athlete participated in various activities during the past three days and nights.Total stress state was calculated as the sum of the subscale scores representing stress (stress subscales), and total recovery state was assessed by the sum of the subscale scores representing recovery (recovery subscales).The Copyright ª 2017 National Strength and Conditioning Association test retest reliability of RESTQ-76 Sport has been previously reported (r = 0.51-0.81)(21).The questionnaire was completed 3 times: before the 6-week training mesocycle, PRE-TP and POST-TP.A high mean score in the stress-associated activity scales represents intense subjective strain whereas high mean scores in the recovery-orientated scale represent adequate recovery.Performance tests All tests were conducted 48 hours following a competition or hard physical training to minimize the influence of fatigue on test performance.Participants performed three trials of each test, with 5 minutes of rest between trials and tests.
Copyright ª 2017 National Strength and Conditioning Association command, they got up and sprinted 10 m, touched the cone opposite the start line.Then, they turned back and sprinted down to the cones placed at the middle of the course.Next, they swerved in and out through four middle cones and once done, sprinted to the top right hand corner cone, ran around the cone and finally sprinted to finish the COD course.COD outcomes were recorded using photocell chronometric devices (Chorno-jump Bosco System).The infrared timing gates were positioned at the start and the finish lines at a height of 1 m.This test has been reported to be a highly reliable and valid measure of a general athletic ability to change direction (37) (COD ICC = 0.91).****Figure 1 near here**** Running acceleration was assessed by a 10-m test.The time in sprinting 10 m as fast as possible was recorded using photocell chronometric devices (Chorno-jump Bosco System).The test began from a static starting position with the toe of the preferred forward foot behind the starting line.The photocells were positioned in a straight direction and timing started when the first photocell was crossed.Time was measured to the nearest 0.01 s. (Sprint ICC = 0.88).
Copyright ª 2017 National Strength and Conditioning Association fatigue and illness.Scheduling training duration reductions while maintaining intensity should be considered by strength and conditioning coaches when designing their preseason training programs to optimize soccer players' physical capacities and stress-recovery state at the onset of the competitive season (25).
Copyright ª 2017 National Strength and Conditioning Association important for it.Numerous factors such as tactics or motivation, which are not necessarily influenced by training periodization, could influence better final results in soccer matches.More studies are needed to further investigate the effects of tapering on other relevant aspects influencing a soccer match such as technical and tactical abilities or mental fatigue.In order to evaluate which is the most useful tapering strategy, it would be also interesting to assess the effect of different tapering modalities in terms of shorter or longer duration, amount of intensity reductions or number of training variables modified.
performance and to reduce stress at the onset of the competitive season.Coaches should consider that two weeks of step-taper characterized by decreasing TL 50% through reduction of training session duration while maintaining intensity can improve lower-limbs muscle power and acceleration ability while reducing the perception of stress.At a practical level, these improvements may positively influence soccer players' performance.Copyright ª 2017 National Strength and Conditioning Association

Figure 1 .
Figure 1.Illustration of the Illinois COD test.

Figure 2 .
Figure 2. Internal Training Load during training and during tapering.Data mean ± SD; 95% confidence interval in brackets.# Significant interaction group x time from the between-groups analysis.*Significant results within-subject pre/post taper period (p < 0.05).COD: change of direction; GC: control group; GE: experimental group; PRE-TP: pre-tapering; POST-TP: post-tapering; η 2 p : partial eta-squared.Copyright ª 2017 National Strength and Conditioning Association Copyright ª 2017 National Strength and Conditioning Association Figure 2 shows the mean weekly ITL completed by the team during the progressive overload training period as well as the ITL completed by the EG and CG during the tapering period.During the training period ITL was progressively ****Figure2near here**** Table1shows the physical condition parameters evaluated before and after tapering for both EG and CG.The between-groups analysis showed a significant time x group interaction for the lower limb muscle power test (F and POST-TP (945.3 ± 98.7 W/kg vs. 950.0±113.3W/kg respectively; p > 0.05; ES = 0.04).Moreover, a significant time x group interaction was also found for ****Table1near here**** Total stress (Σ 10 stress subscales) and total recovery (Σ 9 recovery subscales) were not significantly different from pre-to post-training period (p > 0.05).Total stress and total recovery pre-tapering vs. post-tapering are shown in table 2. The between-groups analysis showed a significant time x group respectively; p > 0.05; ES = 0.4).The between-groups analysis showed a significant time x group interaction for total recovery (F 1,20 = 14.4; p < 0.001; η 2 usefulness to quantify TL during a periodized program and reflects the decrease in training volume in the tapering group.
Copyright ª 2017 National Strength and Conditioning Association throughout a season.J Strength Cond Res 27: 20-30, 2013.34.Slattery, KM, Wallace, LK, Bentley, DJ, and Coutts, AJ.Effect of training load on simulated team sport match performance.Appl Physiol Nutr Metab 33. Silva, JR, Magalhães, J, Ascensão, A, Seabra, AF, and Rebelo, AN.HP, et al.How much is too much?(Part 1) International Olympic Committee consensus statement on load in sport and risk of injury.Br J Sports Med 50: 1030-1041, 2016.37. Stewart, PF, Turner, AN, and Miller, SC.Reliability, factorial validity, and interrelationships of five commonly used change of direction speed tests.Copyright ª 2017 National Strength and Conditioning Association

Table 1 .
Physical condition results of both groups at different time points.

Table 2 .
REST-Q recovery-stress results of both groups at different time points.