Effects of warm-up duration on acute physical performance in highly trained male futsal players

Abstract

Warm-up is a traditional pre-match routine that aims to enhance players’ readiness to subsequent activity. Manipulating the warm-up structure may be important to enhance acute performance. This study aimed to investigate the effects of different warm-up durations on futsal players’ physical performance. Twelve highly trained male futsal players participated in this study during the in-season. All players performed three different warm-up protocols on consecutive days that differed on its total duration: normal (28-minute), short (15-minute) and very short (10-minute). All protocols included the same exercises, performed in the same sequence and with equal time percentage. Testing included 5 and 10 m linear sprint, 505 change of direction, countermovement jump (CMJ) and reactive strength index (RSI) and was performed in three different moments: pre warm-up, post warm-up and post10’ warm-up. CMJ and RSI improved in all protocols at post warm-up, with greater effects observed after very short protocol. However, no effects were observed at post10’ for vertical jump after all protocols. Sprint was improved in post warm-up after short and very short warm-up. Normal warm-up promoted positive effects in sprint at post10’. None of the protocols promoted positive effects in COD at post10’. Very short warm-ups appear to positively influence jumping and running performances, although these effects may be attenuated over time. Normal warm-ups could be valid for maintaining readiness during longer inactive periods that may characterize pre-match routines. Also, different responses may emerge from the same warm-up structure, which reinforces the need of adjusting warm-up according to players’ individual profiles.

Keywords

Countermovement jump potentiation effect pre-match routine reactive strength index running

Introduction

In team sports, pre-match warm-up activities are accepted to be beneficial to the improvement of the acute performance and are widely used by practitioners and coaches. In fact, warm-ups are known to alter temperature, metabolic, psychological and neuromuscular mechanisms that may be important to subsequent performance.¹ Acute positive effects on performance may be linked to the increase of muscle temperature and muscle activation but may be inhibited by residual fatigue.^2,3 Thus, different warm-up configurations may influence such factors in different ways, which may play an important role in players’ acute performance outcomes.

A well-balanced warm-up may rely on the manipulation of different variables such as duration, sequence of tasks, intensity and the characteristics of the different tasks.⁴ Recent literature highlighted the effects of manipulating warm-up duration on subsequent performance.^5–9 The duration of warm-up protocols in team sports typically ranges from 5 to 40 minutes. Considering the necessary balance between potentiation and fatigue, one might raise some questions regarding the effectiveness of protocols with such variation in duration. A systematic review reported that a warm-up protocol lasting more than 20 minutes could compromise acute potentiation, proposing a total time of 10 to 15 minutes in order to avoid fatigue and provide more time for eventually considering adding another warm-up strategies (e.g. Refs.^4,10). Several other studies are in line with this suggestion while showing positive effects of shorter warm-up protocols, and reporting that longer routines could lead to an impartment of player's performance due to the higher perceived exertion and excessive fatigue.^11,12 Particularly in football but also in futsal, although several studies have investigated the effects of warm-up duration, best practices are not consensual and they remain doubtful. Thus, robust evidence is needed to establish practical applications for real world scenarios.

Futsal is characterized by short-term high intensity actions performed in a small area with a fast-paced rhythm characterized by a match play with short recovery time between intense activities.¹³ Players must have a combination of strength, power, speed, endurance and agility. This physical profile is crucial due to intermittent high-intensity actions such as sprinting, change of direction and the ability to accelerate and decelerate with and without the ball are key to achieve a high level performance.¹⁴ In this regard, pre-match warm-up routines play an important role to help players to cope with these physical demands and acutely enhance player's performance at the start of the match under similar informational and contextual environment compared to the upcoming match. Futsal pre-match routines typically include an inactive time gap between the end of the warm-up and the start of the match. Thus, it is key to understand how the warm-up structure influences players’ performance at the start of the match, taking in consideration an official time gap of 10 to 15 minutes between the end of the warm-up and the beginning of the match.

In a recent study with elite futsal teams, a pre-match warm-up model emerged with a total duration of 27.5 minutes that included nine major tasks.¹⁵ An observational and non-experimental descriptive design was used to collect data and results showed that intensity progressively increased during warm-ups, mainly because of the increase in the number of accelerations and decelerations per minute. Team sport coaches traditionally prioritize open-skill activities, stressing competitive and non-competitive specific tasks, thus helping pre-match warm-up routines to establish a condition able to prepare players for the upcoming game.^15,16 However, as aforementioned, coaches usually prescribe warm-ups in futsal lasting close to half an hour. Therefore, this study aimed to investigate the effects of manipulating warm-up duration, maintaining the sequence and number and type of tasks, on running and jumping performances of futsal players.

Methods

Study design

A repeated measures design was conducted to evaluate three warm-up protocols in a randomized sequence during three consecutive days, separated by 24 hours. All players participated in the same randomized protocol in each day. For all protocols, warm-up dynamics (e.g. exercise tasks and sequence) were based on an elite futsal model.¹⁵ Thus, protocols only differed in the total duration of the WU: normal: 27.5 minutes (NormalWU); short: 15 minutes (ShortWU); and very short: 10 minutes (VShortWU). Warm-up durations for ShortWU and VShortWU interventions were defined based on approximately 1/2 and 1/3 of the NormalWU reference. These durations also allowed to include all the WU activities proposed by Silva et al.,¹⁵ since all protocols had the same relative “weight” of the different exercise categories that emerged from the elite model (see Table 1). Testing included running and jumping variables and was performed in three different moments: before WU (PreWU), immediately after WU (PostWU) and 10 minutes after WU (Post10’WU). This timeline represents real world pre-match scenarios that typically include a 10-minute interval between the end of WU and the beginning of the match (see Figure 1).

Figure 1.

Schematic representation of protocol timeline.

Table 1.

Time of each exercise category in all warm-up protocols.

Activity (minutes)	Normal WU	Short WU	VShort WU
Futsal-specific skills without opposition	7.3	4.2	2.6
Stretching	2.0	1.1	0.8
Futsal-specific skills with opposition	4.9	2.5	1.8
Futsal-specific shooting without opposition	8.3	4.3	2.7
Futsal-specific shooting with opposition	4.0	2.2	1.6
Sprinting	1.0	0.7	0.5
Total warm-up routine	27.5	15.0	10.0

Participants

Twelve highly trained.¹⁷ male futsal players (22.6 ± 6.7 years, 1.78 ± 0.06 m, 75.3 ± 6.0 kg) from one Portuguese second division team participated in this study. A medical staff cleared all players to take part of training and match routines before the beginning of the study. The study was conducted during the in-season period with a weekly schedule of five field training sessions (≈90 minutes duration, in the evening) and an official match in the weekend. Goalkeepers were not considered for the study due to the high specificity of goalkeeping activities during WU routines. All players were informed about the study design, requirements and procedures, and their informed consent was obtained. Players were invited to participate 15 days before the beginning of the study and were free to withdraw from the study at any time. The investigation was approved by the local Institutional Research Ethics Committee and followed the recommendations of the Declaration of Helsinki.

Data collection

Evaluations were performed at the same time of the day (8 pm) in an indoor facility with official match surface and similar environmental conditions (22–23 °C). As mentioned before measures were recorded Pre WU, PostWU and Post10’WU, respectively. As futsal requires players to perform repeated short-term high-intensity actions such as jumping, sprinting and changes of direction,¹⁴ testing included countermovement jump (CMJ), reactive strength index (RSI), linear sprint (5 and 10 m) and change of direction speed test (505).

CMJ and RSI were performed on an Optojump device (Microgate, Italy). Optojump is a valid and reliable instrument to measure jumping performance.¹⁸ For CMJ, participants were asked to start standing upright. When ready, the athlete squatted down until the knees were bent at 90 degrees, then immediately jumped vertically as high as possible. Their hands should be on the hips throughout the test. To evaluate RSI, players were asked to perform a depth jump from a 20 cm box and instructed to jump as high as possible with the shortest contact time as possible with the ground.^19,20 The RSI was calculated based on the following formula: RSI = Jump Height/Ground Contact Time. This test allows to evaluate the ability of players to rapidly change from eccentric motion to a concentric contraction and could be associated to the maximal horizontal deceleration ability.²¹ Subjects performed two maximal attempts for each jump with a 30-second interval. The best trial was recorded for analysis.

Linear sprint (5 and 10 m) and 505 tests were evaluated in the same attempt. For that purpose, three infrared timing gates (Witty, Microgate, Italy) were placed at a starting line, 5 and 10 m. This technology is considered a reference tool for measuring sprint performances.²² For the 505 test, the participants were asked to run 15 m before performing a 180-degree change of direction (marked by a turning point) with the dominant leg.²³ The time was recorded from when player first crossed the 5 m marker and stopped when the player crossed again that marker (5 m up and back, for 10 m in total). During the 505 test, linear 5 m and 10 m split times were recorded. The participants were asked to start all running tests 0.5 m behind the starting line. For all running test two trials were allowed with a 90-second interval between trials. Sprint and 505 tests were performed 30 seconds after the jumping tests and players were evaluated in a sequential order to ensure equal time of recovery (≈2 minutes between linear sprint and 505 tests) for all participants.

Experimental tasks

The three intervention protocols were structured according to an elite futsal WU model,¹⁵ which means that the exercise categories and its sequence were the same for all protocols. Thus, interventions only differed in the WU total duration (NormalWU vs. ShortWU vs. VShortWU). The % of time spent in each exercise category was matched across protocols (see Table 1). The WU activities consisted of close and open skills activities structured as following: two players pass and reception with no movement; three players pass and reception with jogging; dynamic stretching of lower limbs; four against two rondos in a 10 × 10 m²; shooting combinations of two players; tactical combinations of three players; two against one counterattack and 3 × 10 m sprints. All the players were familiarized with the activities since they are sport-specific.

Statistical analysis

Individual and mean changes from PreWU to PostWU and Post10’WU for all considered warm-up durations were graphically represented and the variation from considered moments expressed in percentage variation (mean ± SD). Also, both intra-day (between-players) and day-to-day variability (within-players) in postWU performance was measured as typical error and expressed as a coefficient of variation, CV (%).

After preliminary inspections for distribution and assumptions, data were processed to fit analysis of covariance (ANCOVA, group effect: NormalWU, ShortWU and VShortWU), with postWU and post10’WU tests values as the dependent variable and PreWU values as the covariate. Pairwise differences were assessed with Bonferroni post-hoc. Statistical significance was set at p < 0.05 and calculations were completed using the Jamovi Project (Computer Software Version 1.2, 2020).

An estimation techniques approach was carried to overcome the shortcomings associated with traditional N-P null hypothesis significance testing.^24,25 The individual and mean changes were graphically presented according to the different evaluation moments (i.e. PreWU, postWU and post10’WU) for the considered variables: 5 m and 10 m sprint, 505 test, CMJ and RSI. Afterwards, the Cohen's d_unbiased (d_unb) with 95% confidence intervals (CI) as effect size (ES) (an unbiased estimate has a sampling distribution whose mean equals the population parameter being estimated) was applied to identify pairwise differences for each group and considered the following evaluations moments: preWU versus postWU, preWU versus post10’WU and postWU versus post10’WU.²⁴ Thresholds for effect size statistics were: 0.2, 0.5, and 0.8 for small, medium, and large.²⁶

Results

The summary of findings from the ANCOVA for group factor is presented in Table 2. Individual and mean changes from preWU to post10’WU for performance measures are shown in Figure 2. Complementary, the d_unb with 95% CI according to time windows comparisons are presented in Figure 3.

Figure 2.

Cohen's dunbiased for within comparison of the % variation from the pre- to post-test protocols. Error bars indicate uncertainty in true mean changes with 95% confidence intervals.

Figure 3.

Individual and mean changes from preWU to post10’WU for 5 and 10 m sprint, 505 test, counter movement jump (CMJ) and reactive strength index (RSI). Black lines represent the group mean with standard deviation while grey represents individual changes.

Table 2.

Analysis of coefficient of variation.

Variables	Normal WU			Short WU			Very Short WU
Variables	PostWU – PreWU	Post10’WU – PreWU	Post10’WU – PostWU	PostWU – PreWU	Post10’WU – PreWU	Post10’WU – PostWU	PostWU – PreWU	Post10’WU – PreWU	Post10’WU – PostWU
5-m sprints	Δ (%) = -2.19 ± 4,68	Δ (%) = -2.85 ± 4.10	Δ (%) = -0.53 ± 4.97	Δ (%) = -1.80 ± 3.23	Δ(%) = -0.98 ± 4.03	Δ (%) =0.89 ± 4.06	Δ (%) = -3.66 ± 5.71	Δ (%) = -0.69 ± 4.54	Δ (%) =3.46 ± 7.97
10-m sprints	Δ (%) = -1.66 ± 3.58	Δ (%) = -1.75 ± 3.40	Δ (%) = -0.03 ± 3.05	Δ (%) = -2.37 ± 1.79	Δ (%) = -1.25 ± 2.67	Δ (%) =1.16 ± 2.36	Δ (%) = -3.11 ± 3.50	Δ (%) = -0.59 ± 2.53	Δ (%) =2.71 ± 4.05
505 test (505), s	Δ (%) =0.87 ± 3.80	Δ (%) =1.45 ± 3.44	Δ (%) =0.62 ± 2.48	Δ (%) =0.69 ± 2.04	Δ (%) =0.27 ± 1.98	Δ (%) = -0.38 ± 2.63	Δ (%) =0.14 ± 4.91	Δ (%) = -0.21 ± 3.82	Δ (%) = -0.13 ± 6.02
Countermovement jump (CMJ), cm	Δ (%) = 3.32 ± 5.76	Δ (%) = -2.70 ± 6.22	Δ (%) = -5.72 ± 5.39	Δ (%) =3.35 ± 4.91	Δ (%) = -3.30 ± 6.22	Δ (%) = -6.37 ± 5.17	Δ (%) =7.00 ± 4.91	Δ (%) = -1.96 ± 4.96	Δ (%) = -8.18 ± 6.35
RSI m/s	Δ (%) =2.19 ± 13.98	Δ (%) = -5.58 ± 13.50	Δ (%) = -6.16 ± 16.40	Δ (%) =4.80 ± 13.24	Δ (%) = -1.42 ± 12.05	Δ (%) = -5.58 ± 8.26	Δ(%) =13.63 ± 22.08	Δ (%) = -0.26 ± 15.56	Δ (%) = -10.81 ± 11.52

Abbreviations: PreWU – Test before Warm-up; PostWU – Test immediately after Warm-up; Post10’WU – Test 10 minutes after Warm-up.

The comparisons between groups showed no significant differences but results analysis presented clear trends in the athletes performances regarding different WU duration and time windows.

Linear sprint results (5 and 10 m sprint) showed similar pattern. All WU durations improved player's performance when comparing preWU and PostWU moments, with VShortWU having the greatest improvement (5 m, −3.7 ± 5.7%, Cohen's d with 95% of CI: −0.66 [-1.40, 0.004], moderate effect size, ES and 10 m, −3.1 ± 3.5%, −0.68 [-1.29, −0.149], moderate ES). ShortWU showed improvements in 10 m linear sprint postWU −2.4 ± 1.8%, −0.50 [-0.851, −0.200], moderate effect size. Taking in consideration PreWU and Post10’WU the enhancement effect is lower in all WU durations and Normal WU had a better response than the other WU durations (5 m, −2.9 ± 4.1%, −0.47 [-0.956, −0.033], small ES and 10 m, −1.8 ± 3.4%, −0.37 [-0.863, 0.09], small ES).

The COD assessment through 505 test displayed trivial effects in response to all warm-up durations along all timelines.

Jumping tests followed the same trend observed in linear sprint with improvement of player's performance PostWU in all WU durations. However, this enhancement was greater when VShort WU was applied (7.0 ± 4.9%, 0.55 [0.246, 0.915], moderate ES and 13.6 ± 22.1%, 0.42 [-0.14, 1.02], small ES) in CMJ and RSI, respectively. When comparing PreWU and Post10’WU, trivial effects were observed in all protocols.

Discussion

In general, results revealed that WU duration may promote different outcomes regarding physical performance of futsal players with distinct trends along the timeline after the end of the WU. However, none of the interventions promoted improved performance in the tests 10 minutes after the conclusion of the WU, which coincides with the start of the match during a competitive setting.

All WU durations promoted positive effects at postWU in linear running and jumping performances, particularly in the CMJ as also suggested in a previous study.²⁷ VshortWU promoted performance enhancements at postWU in all tests, except for 505. However, 10 minutes after VshortWU performance was impaired in all variables. ShortWU activities had positive effects in the sprinting and jumping tests after the WU, but this enhancement was dissipated in the subsequent 10 minutes time line. Finally, NormalWU had a similar global trend to the one seen in the others WU durations but with a less pronounced effect. These results suggest the duration is a key variable that may influence the acute potentiation magnitude and timeline of effects in futsal.

Acute performance potentiation is the result of the balance between the enhancement effect provided by the activities and the fatigue that these tasks may promote in players’ readiness status.²⁸ In this regard, VshortWU was very effective in the linear sprint and jumping performance immediately after WU, probably due to the fact that the shortest volume of activities had the best balance of promoting potentiation with low values of fatigue to the players. In fact, recent studies suggested that short duration WU can have the desired potentiation effect in less time and with a better time management strategy, allowing coaches to have more time to other crucial activities before a match. In addition, this choice can avoid taxing the muscular and metabolic system of the players since shorter WU time did not induce fatigue and maintained the performance enhancement effect.^7,8

However, one of the main results of this study may raise some questions regarding the best option for coaches if we consider a traditional pre-match protocol. NormalWU was more interesting in promoting positive effects at 10 minutes after the WU, particularly in linear sprint performance. The higher volume of actions performed in this WU may have resulted in a more pronounced and/or long-lasting potentiation effect that was apparent even after 10 minutes. These activities are particularly relevant in futsal because they are associated with the match key actions such as 1 × 1 situations, counter-attacks or quick movements to score goals.¹⁴ When adding the 10 minutes rest period, that is mandatory in official matches and that may last up to 15 minutes, the shorter durations WU lost the potentiation effect observed at postWU. This response could influence the ability to perform physically at a high level in the first minutes of the match. On other hand, the longer duration WU was able to maintain a performance enhancement effect through this time window. That is, longer transition between WU and competition may require a longer WU duration, allowing players to achieve a well-balanced state at the beginning of the match.

Change of direction ability is key to player's performance during a futsal match due to its presence during on ball and off ball movements and the rapid changes of activity required during the match.^14,29 Accordingly, pre-match WU protocols should aim to address this need. Nonetheless, the results observed suggest that all warm-up durations were unable to achieve that goal, since in COD test trivial results were noticed along the entire timeline. This may be associated with the type of tasks used in futsal warm-up. Other possibility could be related with the need of futsal warm-up to include high number of eccentric work, increasing the number of accelerations and decelerations.³⁰

The RSI performance confirmed the need for activities with this specific motor pattern. Rate of force development is highly influenced by the profile of the activities performed and intended ballistic efforts seems to have a major role in the development of this ability.³¹

The opposite trends identified along the timeline bring to the discussion a new way of looking to the pre-match warm-up protocol. Coaches and team staff intention is to prepare the players to start the match at the highest performance level as possible. In order to achieve this goal, official match timeline has to be taken in consideration, otherwise coaches could be developing strategies concerning this acute performance enhancement moment with some misconceptions. Although potentiation time windows are not consensual due to the large number of factors that could influence the relationship between potentiation and fatigue, some studies report that temperature mechanism could be the most important mediator of performance enhancement.¹ In fact, although recovery intervals may fluctuate individually, literature reports that optimal recovery intervals to maximize subsequent activity may range from 5 to 12 minutes.³² The longer time of recovery intervals in which was observed potentiation effects was promoted through the use of close activities with the same motor pattern than was tested and by that mean more suitable to be able to endure this positive effect.³³ This fact suggests that the use of some close skill tasks related to the most important abilities of a futsal match may be advised to coordinate the official match timeline and the potentiation time window coordinated with the most suitable WU duration to our competitive context.

Finally, individual variability was very noticeable in the results of all tests, particularly in the Post10’WU. These different responses by players could be attributed to several factors such as conditioning status, level of training or physical qualities.² Therefore, coaches should be aware of this possibility and prepare individual or group activities in order to achieve the best potentiation effect in all players at the start of the match. These results may be magnified by the use of open-skill activities of the elite Futsal model warm-up protocol used that could have added some inconsistency in the behavior of the players during activities where they do not have necessarily the same load because of the “chaotic” nature of the playing situations that are the core of the WU protocol.

This study was based in a warm-up model that emerged from a previous investigation, which means that caution should be applied when interpreting the results. In fact, manipulating duration in different warm-up designs may lead to different acute performance outcomes. Future investigations should explore the effects of duration in different warm-up structures and in other sports.

Conclusions

Duration is a key variable of the futsal WU structure and may have an important impact on subsequent performance. Vshort WU appear to be the most interesting strategy to induce acute performance enhancements, however such effects may be attenuated over time. This means that short duration WU should be placed close to the start of the match. Normal WU may be more advisable to perform during pre-match routines that include inactive periods (e.g. 10 minutes) between the end of the WU and the start of the match. Despite of these trends, it is important to notice that players’ responses to the same WU structure may be different, which reinforce the need to individualize routines according to individual players’ physical profiles.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Nuno Silva

Bruno Gonçalves

References

McGowan

Pyne

Thompson

, et al. Warm-Up strategies for sport and exercise: mechanisms and applications. Sports Med 2015; 45: 1523–1546.

Blazevich

Babault

. Post-activation potentiation versus post-activation performance enhancement in humans: historical perspective, underlying mechanisms, and current issues. Front Physiol 2019; 10: 1359.

Cuenca-Fernandez

Smith

Jordan

, et al. Nonlocalized postactivation performance enhancement (PAPE) effects in trained athletes: a pilot study. Appl Physiol Nutr Metab 2017; 42: 1122–1125.

Silva

Neiva

Marques

, et al. Effects of warm-up, post-warm-up, and re-warm-up strategies on explosive efforts in team sports: a systematic review. Sports Med 2018; 48: 2285–2299.

Williams

Gillham

Highton

, et al. The influence of warm-up duration on simulated rugby league interchange match performance. Sci Med Football 2021; 5: 137–143.

Mujika

de Txabarri

Maldonado-Martin

, et al. Warm-up intensity and duration's effect on traditional rowing time-trial performance. Int J Sports Physiol Perform 2012; 7: 186–188.

Romaratezabala

Nakamura

Castillo

, et al. Influence of warm-up duration on physical performance and psychological perceptions in handball players. Res Sports Med 2018; 26: 230–243.

Yanci

Iturri

Castillo

, et al. Influence of warm-up duration on perceived exertion and subsequent physical performance of soccer players. Biol Sport 2019; 36: 125–131.

van den Tillaar

von Heimburg

. Comparison of two types of warm-up upon repeated-sprint performance in experienced soccer players. J Strength Cond Res 2016; 30: 2258–2265.

10.

Zois

Bishop

Ball

, et al. High-intensity warm-ups elicit superior performance to a current soccer warm-up routine. J Sci Med Sport 2011; 14: 522–528.

11.

Zois

Bishop

Aughey

. High-intensity warm-ups: effects during subsequent intermittent exercise. Int J Sports Physiol Perform 2015; 10: 498–503.

12.

van den Tillaar

Vatten

von Heimburg

. Effects of short or long warm-up on intermediate running performance. J Strength Cond Res 2017; 31: 37–44.

13.

Spyrou

Freitas

Marin-Cascales

, et al. External match load and the influence of contextual factors in elite futsal. Biol Sport 2022; 39: 349–354.

14.

Spyrou

Freitas

Marin-Cascales

, et al. Physical and physiological match-play demands and player characteristics in futsal: a systematic review. Front Psychol 2020; 11: 569897.

15.

Silva

Travassos

Goncalves

, et al. Pre-match warm-up dynamics and workload in elite futsal. Front Psychol 2020; 11: 584602.

16.

Dello Iacono

Vigotsky

Laver

, et al. Beneficial effects of small-sided games as a conclusive part of warm-up routines in young elite handball players. J Strength Cond Res 2021; 35: 1724–1731.

17.

McKay

AKA

Stellingwerff

Smith

, et al. Defining training and performance caliber: a participant classification framework. Int J Sports Physiol Perform 2022; 17: 1–15.

18.

Glatthorn

Gouge

Nussbaumer

, et al. Validity and reliability of Optojump photoelectric cells for estimating vertical jump height. J Strength Cond Res 2011; 25: 556–560.

19.

Van Hooren

Zolotarjova

. The difference between countermovement and squat jump performances: a review of underlying mechanisms with practical applications. J Strength Cond Res 2017; 31: 2011–2020.

20.

Flanagan

Ebben

Jensen

. Reliability of the reactive strength index and time to stabilization during depth jumps. J Strength Cond Res 2008; 22: 1677–1682.

21.

Jarvis

Turner

Read

, et al. Reactive strength index and its associations with measures of physical and sports performance: a systematic review with meta-analysis. Sports Med 2022; 52: 301–330.

22.

Haugen

Buchheit

. Sprint running performance monitoring: methodological and practical considerations. Sports Med 2016; 46: 641–656.

23.

Sheppard

Young

. Agility literature review: classifications, training and testing. J Sports Sci 2006; 24: 919–932.

24.

Cumming

. Understanding the new statistics: effect sizes, confidence intervals, and meta-analysis. New York: Routledge, Taylor & Francis Group, 2012.

25.

Tumkaya

Aryal

, et al. Moving beyond P values: data analysis with estimation graphics. Nat Methods 2019; 16: 565–566.

26.

Cohen

. Statistical power analysis for the behavioral sciences. New York: L. Erlbaum Associates, 1988.

27.

Loturco

D'Angelo

Fernandes

, et al. Relationship between sprint ability and loaded/unloaded jump tests in elite sprinters. J Strength Cond Res 2015; 29: 758–764.

28.

Wilson

Duncan

Marin

, et al. Meta-analysis of postactivation potentiation and power: effects of conditioning activity, volume, gender, rest periods, and training status. J Strength Cond Res 2013; 27: 854–859.

29.

Ribeiro

Goncalves

Coutinho

, et al. Activity profile and physical performance of match play in elite futsal players. Front Psychol 2020; 11: 1709.

30.

Chaabene

Prieske

Negra

, et al. Change of direction speed: toward a strength training approach with accentuated eccentric muscle actions. Sports Med 2018; 48: 1773–1779.

31.

Aagaard

Simonsen

Andersen

, et al. Increased rate of force development and neural drive of human skeletal muscle following resistance training. J Appl Physiol 2002; 93: 1318–1326.

32.

Dobbs

Tolusso

Fedewa

, et al. Effect of postactivation potentiation on explosive vertical jump: a systematic review and meta-analysis. J Strength Cond Res 2019; 33: 2009–2018.

33.

Mina

Blazevich

Tsatalas

, et al. Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up. Scand J Med Sci Sports 2019; 29: 380–392.