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Abstract

BACKGROUND:

Small-sided games are a popular training method that have shown its effectiveness in improving athletic performance in football players.

OBJECTIVE:

To compare the acute physiological and neuromuscular responses and time-motion characteristics during small-sided games played with and without wildcard players.

METHODS:

Sixteen amateur male football players completed two small-sided games protocol: 4-a-side and 4-a-side with wildcard players. Time-motion characteristics during games, muscular performance parameters before and after small-sided games protocols, physiological response in terms of heart rate and muscle oximetry and rate of perceived exertion were collected.

RESULTS:

Both small-sided games formats induced changes in sprint performance (before-after comparison), in the rate of perceived exertion, heart rate-related variables and time-motion parameters ( $p<$ 0.05). In a comparison between small-sided games formats, lower values of oxygen saturation, heart rate, rate of perceived exertion and time-motion parameters ( $p<$ 0.05) were reported during small-sided games with wildcard players in both working and recovery periods.

CONCLUSIONS:

The inclusion of wildcard players during small-sided games cause a reduction in perceptual, physiological demands and time-motion parameters when compared to control condition.

Keywords

Time-motion floater high-intensity training conditioning games GPS device soccer

1. Introduction

Small-sided games (SSGs) are a popular training method that has shown its effectiveness in improving athletic performance in football players [1, 2, 3]. Since it has been suggested that the maximum benefits in sports are achieved when the training stimuli are similar to competitive demands [4], it is worth noting that SSGs are characterized by simulating real match conditions [3, 5]. In that context, this training method (i.e., SSG) seems to be an efficient and suitable option for the development of particular physical characteristics of football players [6].

Additionally, SSGs demands can vary by modifying variables such as number of players [7], pitch area [8] or the playing rules (e.g., with or without wildcard players) [9] among others. Determining the acute effects of those alterations on internal and external loads and time-motion characteristics would facilitates the training design process and allows a better integration of SSGs within the whole football training periodization [3].

In competition matches, frequent situations of low and high inequality occur between teams. For example, when a player receives a red card, leaving one of the team with a lower number of players. However, most researches confronted teams that had the same number of players (i.e., 5-a-side, 3-a-side, 2-a-side), with a limited body of evidence focused on describing game imbalance situations, from which controversies have emerged. A previous study reported no differences between the fixed and variable (i.e., wildcard) SSGs formats, in terms of time-motion characteristics and physiological responses [10]. Other work showed that playing in low-inferiority (4 vs. 5 or 4 vs. 3) induced higher physiological demands compared to high-inferiority (4 vs. 7) [11]. Another study reported that the incorporation of wildcard players reduced the heart rate (HR) during different SSGs formats [12]. In addition, the effects of different types of wildcard players during SSG (e.g., without, with internal or with internal and external wildcard players) have been studied, showing that the inclusion of only internal wildcard players during SSG did not affect the variables studied when compared to SSG without wildcard players [9]. Nevertheless, the inclusion of internal and external wildcard players reduced HR, rate of perceived exertion (RPE) and dribbling actions when compared to SSG without wildcard players [9]. The lack of consensus on this topic, owing to the heterogeneity that exists among study protocols, demands further research to clarify the effects of using wildcard players within of SSGs.

Although the inclusion of wildcard players has been reported [9, 11] to affect a number of variables within the SSGs, no previous studies have compared the physiological and neuromuscular responses to SSG played with and without wildcard players in amateur senior football players. Additionally, the comparison of the influence of SSG played with and without wildcard players on time-motion characteristics has not yet been investigated. In an attempt to highlight the effects of including a wildcard player in a SSG from a multidisciplinary standpoint (i.e., physiological, neuromuscular and external load variables), describing the acute response to these protocols, typical in training in this sport modality, can be of great interest to coaches in order to know which type of SSG should be used depending on the target. Therefore, the aim of this study was to compare the acute physiological and neuromuscular responses and time-motion characteristics during SSGs played with and without wildcard players in amateur senior football. It was hypothesized that SSG played with wildcard players would obtain lower values for the variables studied when compared to SSG played without wildcard players.

2. Methods

2.1 Participants

Sixteen male football players (age, 23.9 $\pm$ 4.2 years) from two amateur teams with similar competitive and training schedule successfully completed the study. The study was conducted during the in-season. Inclusion criteria to participate in the study were: (i) standard training involving three 2.6 $\pm$ 0.5 hours training sessions per week, and a weekly league match, (ii) participants having been involved in regular football training for at least two years prior to the study, and (iii) players had no injuries in the last six months. Measurements were performed as part of their regular training and testing programme, and players approved the use of these data for research purposes. Moreover, players and coaches were fully informed about the potential risks and benefits derived from participation in the study protocol, and signed and informed consent document before participating in the investigation. The study was conducted in adherence to the standards of the Declaration of Helsinki (2013 version). The local ethics committee approved the informed consent and the study design.

2.2 Experimental approach to the problem

Athletes completed two 4-a-side SSGs protocols with the aim of maintain ball possession as long as possible, with no restrictions regarding number of ball touches. Both SSG formats (i.e. with and without wildcard players) included 4 bouts of 4-min, played without goalkeepers, in a pitch size of 30 $\times$ 20 m, with 2-min of passive recovery between bouts. The acute responses to both SSGs protocols were monitored using physiological, neuromuscular, perceptual and time-motion parameters.

2.3 Procedures

This is a single group repeated-measures study, in which all participants performed the two formats of SSG in two different testing sessions. During both sessions, the participants were monitored for external load (time-motion characteristics) and physiological parameters during one 4-a-side SSG and one 4-a-side SSG with wildcard players, and tested before and after (pre- and post-SSG) for physical fitness assessment (countermovement vertical jump [CMJ], 5-m and 20-m sprint) (Fig. 1). The participants were asked to avoid high-intensity exercise $\geqslant$ 72 h before the testing sessions. The tests were completed in outdoor artificial grass surface, were athletes usually trained and compete. Before testing, athletes completed a typical warm-up. The participants were motivated to perform at maximal intensity in every test. The athletes were familiarization with SSG, as they use them as part of their regular training sessions.

Figure 1.

Schematic of the experimental protocol and variable measurements followed in both SSG formats.

The athletes were randomized to 2 different SSG formats for 2 sessions. Each session was separated by a week. After the pre-SSG (physical fitness assessment), athletes completed one 4-a-side SSG or one 4-a-side SSG with wildcard players (with two internal wildcard players that played with the team in possession of the ball), that were conducted with the aim of maintain ball possession as long as possible, with no restrictions regarding number of ball touches. The two athletes that participated as wildcard players were not analysed for the study. The SSGs included 4 bouts of 4-min, played without goalkeepers, in a pitch size of 30 $\times$ 20 m, with 2-min of passive recovery between bouts. When the ball was kicked out of play, a ball replacement was immediately provided. The SSG was supervised by one of the researchers.

2.4 Outcome parameters

2.4.1 20-m sprint

Sprint evaluation (pre- and post-SSG) was accomplished through a speed test that was carried out in a straight 20-m line [13]. Markers were set up at 5-m and 20-m. Additionally, split sprint time of 5-m was analysed. Based on the method described by Lehance et al. [14], sprint times (s) were measured using two double-light barriers (Witty; Microgate Srl, Bolzano, Italy; accuracy of 0.001 s): (a) at knee height (60 cm) for the departure, (b) at the shoulder height (150 cm) for the arrival, and (c) at intermediate markers (at 5-m). To eliminate reaction time, the participants started from a static position with feet parallel behind the start line. No starting signal was given. The players performed 2 trials with a 3-min recovery in-between. The best trial was recorded for the subsequent statistical analysis.

2.4.2 Countermovement vertical jump (CMJ)

The jumping performance (pre- and post-SSG) was assessed through CMJ test. The participants were highly familiarized with the CMJ technique, as they performed CMJ in their daily training sessions. The CMJ was recorded using the Optojump system (Optojump, Microgate, Bolzano, Italy), which was also used in a similar study [14]. The Optojump system is a valid and reliable device to measure CMJ performance [15]. During the CMJ, subjects were instructed to rest his hands on his hips, foot and shoulders wide apart. Subjects performed a downward movement with no restriction imposed over the knee angle achieved [16], followed by a maximal effort vertical jump [17]. All subjects were instructed to land in an upright position and to bend their knees after landing [17]. Three trials were performed with a 15-s recovery period between them, and the best trial was used for the statistical analysis.

2.4.3 Rating of perceived exertion (RPE)

Global RPE was obtained, immediately after each of the 4 bouts of the SSG (during the recovery between bouts), using the 6-scale [18], to ensure that the perceived effort was referred to the SSG training only. Briefly, the subjects answers were recorded individually, without presence of other players, after the question (in Spanish): “How hard was the SSG?” [9]. All players were familiarized with the RPE scale before the research project started.

Table 1
Physical fitness comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur soccer players ( $n=$ 16)

Variables	Groups	Before	After	$P$ -value (group $\times$ time)
20-m sprint (s)	ExC1	3.11 $\pm$ 0.14	3.15 $\pm$ 0.12	0.022
	ExC2	3.12 $\pm$ 0.09	3.17 $\pm$ 0.09	0.011
$p$ -value (time $\times$ group)	0.703	0.575
5-m sprint (s)	ExC1	1.08 $\pm$ 0.08	1.09 $\pm$ 0.05	0.414
	ExC2	1.09 $\pm$ 0.05	1.11 $\pm$ 0.05	0.119
$p$ -value (time $\times$ group)	0.763	0.380
Countermovement jump (m)	ExC1	39.1 $\pm$ 5.5	38.9 $\pm$ 5.8	0.588
	ExC2	39.1 $\pm$ 5.5	38.6 $\pm$ 5.3	0.227
$p$ -value (time $\times$ group)	0.990	0.895

ExC1 $=$ experimental condition 1 (4-a-side small-sided games); ExC2 $=$ experimental condition 2 (4-a-side small-sided games $+$ 2 internal wildcard players).

2.4.4 Heart rate monitoring (HR)

The HR was recorded at 5-s intervals during the 4-a-side SSG via short-range radio telemetry (Polar Team Sport System, Polar Electro Oy, Finland). It was expressed as a percentage of peak HR (HRpeak) by using generalized equation for predicting HRpeak [19], and were classified into four previously defined intensity zones: Zone 1 ( $<$ 75% HRpeak), Zone 2 (75–84% HRpeak), Zone 3 (85–89% HRpeak), and Zone 4 ( $\geqslant$ 90% HRpeak) [20]. The percentage of time spent within each intensity zone during the SSG was quantified, as well as the percentages of HRpeak (%HRpeak), and average HR (HRaverage) with respect to the calculated through the generalized equation proposed by Tanaka et al. [19]. In addition, the HRpeak reached was recorded during the work and recovery periods of SSG.

2.4.5 Muscle oxygen saturation (SmO ${}_{2}$ ) and total muscle haemoglobin (THb)

The SmO ${}_{2}$ and THb was monitored by near infrared spectroscopy (Moxy, Fortiori Design LLC, Minnesota, USA), which was also used in a similar study [21]. The Moxy was positioned on the participant’s dominant leg, as in a previous study [21], determined by asking the athletes about their preferred kicking leg. The Moxy is a reliable device to measure SmO ${}_{2}$ and THb, validated in a previous study [21].

2.4.6 Time-motion characteristics

Players’ activity was recorded using 20-Hz global positioning system (WIMU PRO ${}^{\text{TM}}$ ) and were analysed using S PRO ${}^{\text{TM}}$ software (RealTrack Systems, Almeria, Spain). The reliability and validity of this technology for monitoring players’ activity during football matches has been previously determined [22]. For data analysis purposes, 4 speed zones were selected: speed zone 1 (standing and walking, 0.1–6.9 km/h), speed zone 2 (low-intensity running, 7.0–12.9 km/h), speed zone 3 (medium-intensity running, 13.0–17.9 km/h), and speed zone 4 (high-intensity running, $\geqslant$ 18.0 km/h) [23, 24]; and 4 acceleration zones: acceleration zone 1 (1.0–1.4 m/s ${}^{2}$ ), acceleration zone 2 (1.5–1.9 m/s ${}^{2}$ ), acceleration zone 3 (2.0–2.4 m/s ${}^{2}$ ), and acceleration zone 4 ( $\geqslant$ 2.5 m/s ${}^{2}$ ) [23]. Similarly to previous studies, sprint distance was established ( $>$ 24.1 km/h) [25]. The total distance travelled, total m/min, total accelerations and decelerations, sprints, average sprint duration, maximal speed reached, average speed and distance travelled within designated speed zones and the number of accelerations within designated zones were all calculated.

2.5 Statistical analysis

Descriptive statistics are represented as mean and standard deviation (SD). Tests of normal distribution and homogeneity (Shapiro-Wilk and Levene’s test, respectively) were conducted on all data before analysis. A Student’s paired $t$ -test was conducted to determine the pre- vs. post-SSG differences in physical fitness assessment (CMJ and sprint test). A repeated measures analysis of variance (ANOVA), with Bonferroni post-hoc test, was used to determine the dynamic of physiological parameters, RPE and time-motion characteristics during the SSG protocol. Data analysis was performed using SPSS (version 22, SPSS Inc., Chicago, IL, USA), and the significance level was set at $P<$ 0.05.

3. Results

3.1 Physical fitness assessment

Table 1 outlines the physical fitness comparison (sprint and jump) between the two different formats of SSGs. No significant differences (Time $\times$ Group) in 20-m sprint, 5-m sprint, or CMJ were found ( $P>$ 0.05). However, significant differences (Group $\times$ Time) were found in 20-m sprint time ( $P<$ 0.05), for both SSG formats.

Table 2
Physiological and perceptual responses comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur football players on bout periods ( $n=$ 16)

Variables	Groups	Bout ${}^{*}$ 1		Bout 2		Bout 3		Bout 4		$P$ -value (group $\times$ time)
Total haemoglobin content (g.dL ${}^{-1}$ )	ExC1	12.1	$\pm$ 0.5	12.2	$\pm$ 0.5	12.1	$\pm$ 0.5	12.1	$\pm$ 0.5	0.137
	ExC2	11.9	$\pm$ 0.4	12.1	$\pm$ 0.5	12.1	$\pm$ 0.5	12.1	$\pm$ 0.5	0.444
$p$ -value (time $\times$ group)		0.678		0.683		0.795		0.726
Muscle oxygen saturation (%)	ExC1	36.3	$\pm$ 15.3	38.4	$\pm$ 17.4	34.0	$\pm$ 13.2	34.3	$\pm$ 15.3	0.542
	ExC2	47.2	$\pm$ 14.6	49.7	$\pm$ 19.7	53.7	$\pm$ 20.7	53.7	$\pm$ 22.0	0.154
$p$ -value (time $\times$ group)		0.168		0.242		0.040		0.060
Rating of perceived exertion (6–20)	ExC1	12.3	$\pm$ 1.5 ${}_{\text{a}}$	13.0	$\pm$ 1.9 ${}_{\text{a,b}}$	13.6	$\pm$ 1.2 ${}_{\text{b}}$	14.5	$\pm$ 1.9 ${}_{\text{c}}$	$<$ 0.001
	ExC2	11.4	$\pm$ 1.4	11.9	$\pm$ 2.3	12.1	$\pm$ 2.4	12.2	$\pm$ 2.0	0.248
$p$ -value (time $\times$ group)		0.094		0.145		0.029		0.002
HR ${}_{\text{peak}}$ (beats. min ${}^{-1}$ )	ExC1	169.12	$\pm$ 23.94	173.93	$\pm$ 17.59	171.37	$\pm$ 20.96	172.25	$\pm$ 18.66	0.205
	ExC2	160.31	$\pm$ 22.62 ${}_{\text{a}}$	167.81	$\pm$ 22.44 ${}_{\text{b}}$	166.87	$\pm$ 17.27 ${}_{\text{a,b}}$	165.18	$\pm$ 21.09 ${}_{\text{a,b}}$	0.011
$p$ -value (time $\times$ group)		0.094		0.145		0.029		0.002
Average heart rate (beats. min ${}^{-1}$ )	ExC1	157	$\pm$ 23.9	161	$\pm$ 19.4	160	$\pm$ 18.6	159	$\pm$ 20.2	0.726
	ExC2	145	$\pm$ 23.4 ${}_{\text{a}}$	155	$\pm$ 21.4 ${}_{\text{b}}$	153	$\pm$ 17.7 ${}_{\text{b}}$	152	$\pm$ 19.7 ${}_{\text{a,b}}$	0.014
$p$ -value (time $\times$ group)		0.147		0.483		0.277		0.273
%HR ${}_{\text{peak}}$ (%)	ExC1	87.0	$\pm$ 10.5	88.9	$\pm$ 8.3	88.5	$\pm$ 6.9	88.3	$\pm$ 8.6	0.689
	ExC2	83.0	$\pm$ 11.2 ${}_{\text{a}}$	88.9	$\pm$ 8.1 ${}_{\text{b}}$	87.6	$\pm$ 6.7 ${}_{\text{b}}$	86.9	$\pm$ 8.4 ${}_{\text{a,b}}$	0.010
$p$ -value (time $\times$ group)		0.309		0.999		0.714		0.656
$<$ 75% HR ${}_{\text{peak}}$ (%)	ExC1	25.6	$\pm$ 34.5	21.3	$\pm$ 30.6	19.6	$\pm$ 32.6	20.5	$\pm$ 34.1	0.752
	ExC2	30.4	$\pm$ 35.2	18.9	$\pm$ 32.1	20.4	$\pm$ 26.6	30.5	$\pm$ 35.7	0.133
$p$ -value (time $\times$ group)		0.702		0.832		0.936		0.427
75–84% HR ${}_{\text{peak}}$ (%)	ExC1	10.3	$\pm$ 8.7	14.5	$\pm$ 10.4	13.7	$\pm$ 15.3	11.6	$\pm$ 11.0	0.789
	ExC2	18.0	$\pm$ 25.0	15.3	$\pm$ 16.1	22.9	$\pm$ 21.6	14.9	$\pm$ 15.9	0.475
$p$ -value (time $\times$ group)		0.251		0.856		0.178		0.505
85–89% HR ${}_{\text{peak}}$ (%)	ExC1	7.7	$\pm$ 5.8	7.5	$\pm$ 7.8	10.7	$\pm$ 13.6	10.8	$\pm$ 10.0	0.679
	ExC2	11.8	$\pm$ 15.4	10.9	$\pm$ 15.3	8.4	$\pm$ 8.5	11.4	$\pm$ 13.6	0.786
$p$ -value (time $\times$ group)		0.325		0.422		0.577		0.892
$>$ 90% HR ${}_{\text{peak}}$ (%)	ExC1	56.4	$\pm$ 30.5	56.8	$\pm$ 32.0	56.0	$\pm$ 31.4	57.0	$\pm$ 32.2	0.998
	ExC2	39.8	$\pm$ 34.0	54.8	$\pm$ 33.3	48.3	$\pm$ 34.7	43.2	$\pm$ 36.6	0.118
$p$ -value (time $\times$ group)		0.156		0.863		0.514		0.267

ExC1 $=$ experimental condition 1 (4-a-side small-sided games); ExC2 $=$ experimental condition 2 (4-a-side small-sided games $+$ 2 internal wildcard players); HR ${}_{\text{peak}}$ $=$ peak heart rate; %HR ${}_{\text{peak}}$ $=$ percentage of HR ${}_{\text{peak}}$ ; $<$ 75% HR ${}_{\text{peak}}$ (%) $=$ the percentage of time spent within that intensity zone; 75–84% HR ${}_{\text{peak}}$ (%) $=$ the percentage of time spent within that intensity zone; 85–89% HR ${}_{\text{peak}}$ (%) $=$ the percentage of time spent within that intensity zone; $>$ 90% HR ${}_{\text{peak}}$ (%) $=$ the percentage of time spent within that intensity zone; ${}_{\text{a,b,c}}$ $=$ different subscript letters indicate significant differences ( $P<$ 0.05) between bouts by bonferroni post-hoc test; ${}^{*}$ : each bout lasted 4 minutes.

Table 3

Physiological responses comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur football players on recovery periods ( $n=$ 16)

Variables	Groups	Recovery ${}^{*}$ between bout 1–2	Recovery between bout 2–3	Recovery between bout 3–4	$P$ -value (group $\times$ time)
Total haemoglobin content (g.dL ${}^{-1}$ )	ExC1	12.4 $\pm$ 0.4	12.2 $\pm$ 0.5	12.4 $\pm$ 0.3	0.139
	ExC2	12.3 $\pm$ 0.3	12.3 $\pm$ 0.4	12.3 $\pm$ 0.3	0.882
$p$ -value (time $\times$ group)		0.432	0.475	0.642
Muscle oxygen saturation (%)	ExC1	66.7 $\pm$ 8.7	65.2 $\pm$ 9.9	61.1 $\pm$ 15.4	0.230
	ExC2	73.9 $\pm$ 7.7	73.7 $\pm$ 7.9	73.9 $\pm$ 9.6	0.996
$p$ -value (time $\times$ group)		0.102	0.078	0.066
HR ${}_{\text{peak}}$ (beats. min ${}^{-1}$ )	ExC1	167 $\pm$ 24.5	169 $\pm$ 20.1	165 $\pm$ 23.1	0.428
	ExC2	159 $\pm$ 22.2	163 $\pm$ 20.2	158 $\pm$ 22.0	0.089
$p$ -value (time $\times$ group)		0.337	0.425	0.342
HR ${}_{\text{average}}$ (beats. min ${}^{-1}$ )	ExC1	143 $\pm$ 17.7	144 $\pm$ 11.3	145 $\pm$ 16.9	0.884
	ExC2	133 $\pm$ 15.4	137 $\pm$ 14.0	131 $\pm$ 13.0	0.262
$p$ -value (time $\times$ group)		0.095	0.144	0.017
%HR ${}_{\text{peak}}$ (%)	ExC1	79.2 $\pm$ 8.8	79.8 $\pm$ 3.4	80.1 $\pm$ 6.7	0.916
	ExC2	76.1 $\pm$ 6.6	78.8 $\pm$ 7.4	75.5 $\pm$ 5.5	0.124
$p$ -value (time $\times$ group)		0.272	0.659	0.041
$<$ 75% HR ${}_{\text{peak}}$ (%)	ExC1	42.1 $\pm$ 34.0	36.8 $\pm$ 33.5	41.5 $\pm$ 38.9	0.798
	ExC2	50.5 $\pm$ 27.8	41.2 $\pm$ 30.0	59.2 $\pm$ 30.8	0.092
$p$ -value (time $\times$ group)		0.452	0.692	0.163
75–84% HR ${}_{\text{peak}}$ (%)	ExC1	29.2 $\pm$ 25.2	26.2 $\pm$ 18.0	22.2 $\pm$ 17.6	0.411
	ExC2	25.5 $\pm$ 17.7	35.2 $\pm$ 26.2	23.2 $\pm$ 18.0	0.072
$p$ -value (time $\times$ group)		0.631	0.265	0.877
85–89% HR ${}_{\text{peak}}$ (%)	ExC1	9.1 $\pm$ 5.8	11.9 $\pm$ 9.3	13.6 $\pm$ 18.9	0.577
	ExC2	12.6 $\pm$ 17.6	4.6 $\pm$ 5.0	4.8 $\pm$ 4.1	0.090
$p$ -value (time $\times$ group)		0.456	0.009	0.078
$>$ 90% HR ${}_{\text{peak}}$ (%)	ExC1	19.6 $\pm$ 16.6	18.9 $\pm$ 13.1	22.7 $\pm$ 25.7	0.807
	ExC2	11.5 $\pm$ 9.2	18.9 $\pm$ 23.8	12.8 $\pm$ 12.8	0.224
$p$ -value (time $\times$ group)		0.097	0.998	0.178

3.2 Physiological and perceptual characteristics

Table 2 outlines the physiological and perceptual responses comparison between the two different formats of SSGs during bout periods. Significant differences (Time $\times$ Group) in SmO ${}_{2}$ , RPE and HRpeak were observed ( $P<$ 0.05) with values lower in 4-a-side SSG with 2 internal wildcard players (except in SmO ${}_{2}$ that correlates negatively with HR). No significant differences (Time $\times$ Group) in THb nor the others HR-related variables were found ( $P>$ 0.05) for both groups. Statistically significant differences (Group $\times$ Time) in RPE for 4-a-side SSG without wildcard players and HRpeak, HRaverage and %HRpeak for 4-a-side SSG with 2 internal wildcard players were found ( $P<$ 0.05). No other differences (Group $\times$ Time) were observed for both groups. Post hoc analysis indicated significant differences between bouts in each experimental condition ( $P<$ 0.05).

Table 3 shows the physiological responses comparison between two different formats of SSGs during recovery periods. Significant differences (Time $\times$ Group) in HRaverage (recovery between bout 3–4), %HRpeak (recovery between bout 3–4) and 85–89% HRpeak (recovery between bout 2–3) were found ( $P<$ 0.05) with values lower in 4-a-side SSG with 2 internal wildcard players. No other differences (Time $\times$ Group nor Group $\times$ Time) were observed ( $P>$ 0.05) for both groups.

3.3 Time-motion characteristics

The time-motion characteristics comparison obtained at each of the 4 bouts of the two SSG formats are indicated in Table 4. The ANOVA results indicated significant differences (Time $\times$ Group) that are shown below. Lower total distance and m/min was observed in the 4-a-side SSG with 2 internal wildcard players versus 4-a-side SSG without wildcard players ( $P<$ 0.01) in the 4 bouts. Greater distance travelled at 0.1–6.9 km/h was observed in 4-a-side SSG with 2 internal wildcard players versus 4-a-side SSG without wildcard players ( $P<$ 0.05) in the 4 bouts. Moreover, greater distance travelled at 7.0–12.9 km/h and 13.0–17.9 km/h was observed in 4-a-side SSG without wildcard players versus 4-a-side SSG with 2 internal wildcard players ( $P=$ 0.001 and $P<$ 0.05; respectively) in the 4 bouts. Greater number of accelerations between 1.0–1.4 m.s ${}^{-2}$ was observed in 4-a-side SSG with 2 internal wildcard players versus 4-a-side SSG without wildcard players ( $P<$ 0.05) in the bout 1. Conversely, lower number of accelerations $\geqslant$ 2.5 m.s ${}^{-2}$ were found in 4-a-side SSG with 2 internal wildcard players versus 4-a-side SSG without wildcard players ( $P<$ 0.01) in the bout 1. Total distance travelled at $\geqslant$ 18.0 km/h and maximal speed was greater in 4-a-side SSG without wildcard players versus 4-a-side SSG with 2 internal wildcard players ( $P<$ 0.05 and $P=$ 0.001; respectively) in the bout 2. Average speed was greater in 4-a-side SSG without wildcard players versus 4-a-side SSG with 2 internal wildcard players ( $P\leqslant$ 0.001) in the 4 bouts. Statistically significant differences (Group $\times$ Time) are shown in Table 4. Post hoc analysis indicated significant differences between bouts in each experimental condition ( $P<$ 0.05).

Table 4
Time-motion characteristics comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur football players on bout periods ( $n=$ 16)

Variables	Groups	Bout ${}^{*}$ 1		Bout 2		Bout 3		Bout 4		$P$ -value (group $\times$ time)
Total distances (m)	ExC1	532	$\pm$ 48.3	515	$\pm$ 59.5	500	$\pm$ 53.4	512	$\pm$ 42.9	0.066
	ExC2	459	$\pm$ 76.1	436	$\pm$ 75.0	432	$\pm$ 78.2	442	$\pm$ 75.8	0.134
$p$ -value (time $\times$ group)		0.003		0.003		0.007		0.003
Total distances at 0.1–6.9 km.h ${}^{-1}$ (m)	ExC1	179	$\pm$ 20.9 ${}_{\text{a}}$	183	$\pm$ 23.7 ${}_{\text{a}}$	200	$\pm$ 28.0 ${}_{\text{b}}$	193	$\pm$ 17.8 ${}_{\text{a,b}}$	0.014
	ExC2	213	$\pm$ 31.3	216	$\pm$ 31.0	226	$\pm$ 31.2	219	$\pm$ 21.9	0.280
$p$ -value (time $\times$ group)		0.001		0.002		0.019		0.001
Total distances at 7.0–12.9 km.h ${}^{-1}$ (m)	ExC1	289	$\pm$ 45.2 ${}_{\text{a}}$	258	$\pm$ 49.3 ${}_{\text{a,b}}$	249	$\pm$ 52.1 ${}_{\text{b}}$	256	$\pm$ 46.7 ${}_{\text{b}}$	0.009
	ExC2	203	$\pm$ 69.4	185	$\pm$ 60.7	171	$\pm$ 64.8	177	$\pm$ 49.0	0.039
$p$ -value (time $\times$ group)		$<$ 0.001		0.001		0.001		$<$ 0.001
Total distances at 13.0–17.9 km.h ${}^{-1}$ (m)	ExC1	62.1	$\pm$ 18.9 ${}_{\text{a,c}}$	67.5	$\pm$ 33.3 ${}_{\text{a}}$	49.9	$\pm$ 27.5 ${}_{\text{b,c}}$	58.1	$\pm$ 12.3 ${}_{\text{a,c}}$	0.045
	ExC2	38.6	$\pm$ 30.6	33.1	$\pm$ 26.9	31.3	$\pm$ 28.5	43.0	$\pm$ 34.6	0.262
$p$ -value (time $\times$ group)		0.014		0.003		0.070		0.111
Total distances at $\geqslant$ 18.0 km.h ${}^{-1}$ (m)	ExC1	1.8	$\pm$ 3.0 ${}_{\text{a}}$	6.5	$\pm$ 6.6 ${}_{\text{b}}$	2.0	$\pm$ 2.3 ${}_{\text{a,b}}$	6.1	$\pm$ 8.2 ${}_{\text{a,b}}$	0.005
	ExC2	3.4	$\pm$ 4.9	1.8	$\pm$ 3.6	3.5	$\pm$ 5.5	3.6	$\pm$ 5.2	0.701
$p$ -value (time $\times$ group)		0.272		0.019		0.310		0.312
Total m/min	ExC1	133	$\pm$ 11.9	128	$\pm$ 14.7	125	$\pm$ 13.4	128	$\pm$ 10.9	0.069
	ExC2	114	$\pm$ 18.7	109	$\pm$ 19.2	107	$\pm$ 19.3	111	$\pm$ 18.9	0.113
$p$ -value (time $\times$ group)		0.002		0.003		0.005		0.003
Total number of accelerations	ExC1	231	$\pm$ 10.7	232	$\pm$ 19.3	233	$\pm$ 13.7	233	$\pm$ 12.2	0.922
	ExC2	229	$\pm$ 17.6	229	$\pm$ 18.7	233	$\pm$ 13.1	235	$\pm$ 12.0	0.316
$p$ -value (time $\times$ group)		0.718		0.693		0.947		0.632
Number of accelerations between 1.0–1.4 m.s ${}^{-2}$	ExC1	36.3	$\pm$ 8.6 ${}_{\text{a}}$	42.8	$\pm$ 11.2 ${}_{\text{a,b}}$	43.1	$\pm$ 8.1 ${}_{\text{a,b}}$	46.8	$\pm$ 4.6 ${}_{\text{b}}$	0.014
	ExC2	43.4	$\pm$ 10.3	42.0	$\pm$ 10.2	47.3	$\pm$ 9.5	47.2	$\pm$ 10.0	0.216
$p$ -value (time $\times$ group)		0.044		0.845		0.185		0.875
Number of accelerations between 1.5–1.9 m.s ${}^{-2}$	ExC1	30.8	$\pm$ 9.2 ${}_{\text{a}}$	36.9	$\pm$ 7.9 ${}_{\text{a,b}}$	36.3	$\pm$ 8.8 ${}_{\text{a,b}}$	39.1	$\pm$ 6.4 ${}_{\text{b}}$	0.010
	ExC2	36.5	$\pm$ 8.8 ${}_{\text{a,b}}$	34.8	$\pm$ 9.0 ${}_{\text{a}}$	36.8	$\pm$ 6.6 ${}_{\text{a,b}}$	41.9	$\pm$ 6.9 ${}_{\text{b}}$	0.036
$p$ -value (time $\times$ group)		0.081		0.495		0.839		0.240
Number of accelerations between 2.0–2.4 m.s ${}^{-2}$	ExC1	25.7	$\pm$ 6.4	27.0	$\pm$ 5.6	28.1	$\pm$ 6.0	28.5	$\pm$ 5.3	0.431
	ExC2	28.2	$\pm$ 5.3	28.3	$\pm$ 7.2	31.6	$\pm$ 5.9	31.2	$\pm$ 6.1	0.094
$p$ -value (time $\times$ group)		0.238		0.569		0.111		0.191
Number of accelerations $\geqslant$ 2.5 m.s ${}^{-2}$	ExC1	138	$\pm$ 19.1 ${}_{\text{a}}$	125	$\pm$ 20.5 ${}_{\text{a,b}}$	126	$\pm$ 13.3 ${}_{\text{b}}$	119	$\pm$ 9.6 ${}_{\text{b}}$	0.002
	ExC2	121	$\pm$ 15.3	124	$\pm$ 19.8	117	$\pm$ 16.6	115	$\pm$ 14.3	0.193
$p$ -value (time $\times$ group)		0.009		0.869		0.118		0.375
Total number of decelerations	ExC1	231	$\pm$ 12.2	229	$\pm$ 10.3	228	$\pm$ 14.3	232	$\pm$ 15.2	0.821
	ExC2	235	$\pm$ 17.0	230	$\pm$ 13.1	229	$\pm$ 13.7	225	$\pm$ 12.7	0.308
$p$ -value (time $\times$ group)		0.501		0.894		0.822		0.149
Maximal speed (km.h ${}^{-1}$ )	ExC1	18.0	$\pm$ 1.5 ${}_{\text{a}}$	19.5	$\pm$ 2.2 ${}_{\text{a,b}}$	18.2	$\pm$ 1.8 ${}_{\text{a,b}}$	19.9	$\pm$ 2.7 ${}_{\text{b}}$	0.004
	ExC2	17.7	$\pm$ 2.3	16.7	$\pm$ 2.2	17.5	$\pm$ 2.7	18.1	$\pm$ 2.4	0.084
$p$ -value (time $\times$ group)		0.620		0.001		0.384		0.060
Average speed (km.h ${}^{-1}$ )	ExC1	7.0	$\pm$ 0.4 ${}_{\text{a}}$	6.8	$\pm$ 0.8 ${}_{\text{a,b}}$	6.5	$\pm$ 0.6 ${}_{\text{b}}$	6.7	$\pm$ 0.5 ${}_{\text{a,b}}$	0.018
	ExC2	5.9	$\pm$ 1.0 ${}_{\text{a}}$	5.5	$\pm$ 0.9 ${}_{\text{a,b}}$	5.4	$\pm$ 1.0 ${}_{\text{b}}$	5.7	$\pm$ 0.8 ${}_{\text{a,b}}$	0.047
$p$ -value (time $\times$ group)		$<$ 0.001		$<$ 0.001		0.001		$<$ 0.001

ExC1 $=$ experimental condition 1 (4-a-side small-sided games); ExC2 $=$ experimental condition 2 (4-a-side small-sided games $+$ 2 internal wildcard players); ${}_{\text{a,b}}$ $=$ different subscript letters indicate significant differences ( $P<$ 0.05) between bouts by bonferroni post-hoc test; ${}^{*}$ : each bout lasted 4 minutes.

4. Discussion

The aim of this study was to compare the acute physiological and neuromuscular responses and time-motion characteristics during SSGs played without and with wildcard players in amateur senior football. The main findings indicated that: (i) Sprinting performance was impaired after both SSG protocols, whereas jumping performance remained unchanged; (ii) Between-protocols differences were found in HRpeak and SmO ${}_{2}$ , and the RPE was lower throughout the 4-a-side SSG with wildcard players protocol than during the 4-a-side SSG without wildcard players; (iii) during the recovery periods, the HRaverage and %HRpeak was higher throughout the 4-a-side SSG without wildcard players than during the 4-a-side SSG with wildcard players; (iv) As for time-motion characteristics, some changes were observed in terms of total distance, distance travelled at different speed, m/min, number of accelerations within designated speed zones, and maximal and average speed for comparison between protocols.

4.1 Physical fitness performance

In this study, the inclusion of wildcard players during a SSG did not affect the sprint and jumping capacities compared to a SSG format without wildcard players. The effect of SSGs on sprint and jump has been previously studied with some controversies reported [2, 26]. The 20-m sprint performance was impaired after the SSG protocols. This finding is consistent with a previous study that reported a higher decline after a similar SSG protocol (3-a-side) [27]. Sprint running involves stretch-shortening cycle muscle function of both lower and upper body musculature with increased metabolic demands [28]. According to a previous study [27], it seems that higher endurance levels are needed in order to maintain performance (sprint performance). Therefore, the fatigue induced by SSG protocols might help explain the reduction in 20-m sprint performance after SSG protocols. On the other hand, CMJ scores did not change after SSG protocols in agreement with another study [26]. This fact can be due and explained by the muscular contraction nature, since both the sprint and jump abilities might respond differentially to (peripheral) fatigue and metabolic perturbations (such as blood lactate accumulation) [29]. The knowledge of these factors may help to coaches to optimize the training control process.

4.2 Physiological and perceptual characteristics

The effects of the inclusion of wildcard players on physiological and perceptual variables during SSG is still not clear [5, 9, 10]. In our study, a lower RPE was recorder during 4-a-side SSG with wildcard players compared to 4-a-side SSG without wildcard players, as in a previous study [9]. When an unequal number of players is introduced with temporary superiority and inferiority numerical situations, it must be taken into account that the players participation in the SSG (i.e., direct and indirect ball participation) is lower than those games played with equal number of players [30]. This may lead to a reduction of individual actions (i.e., 1 vs 1 duel), then decreased RPE [9, 31].

With regard to physiological variables, the inclusion of wildcard players in this study affected the HRpeak and SmO ${}_{2}$ , but not the rest of HR-related variables nor THb during the four bouts of the SSG. The effect of the number of players can alter the intensity in a SSG [3, 5]. However, the intensity may be modified by changing several variables, not only the number of players, such as dimensions of the playing area [20], the athletes roles [9], among other factors that should be considered. In this study, %HRpeak values were similar to those observed in a previous study during a 4-a-side SSG with goals scored without goalkeepers and a 4-a-side SSG with internal wildcard players [9], and similar to a study that analysed a 4-a-side SSG without goalkeepers and only maintenance of the ball [24]. Even though in this study there were not many changes in the HR-related variables by the inclusion of wildcard players, the incorporation of two internal wildcard players during 4-a-side SSG induced higher time spent in zone 1 and zone 2 compared to control condition (without wildcard players), as in a previous study [9], and reduced time spent in zone 4.

When the number of players is increased during a SSG, with the same pitch size and game rules, the intensity (in terms of physiological load) is lower [32]. The presence of wildcard players can become a greater incentive for each team to work harder to gain possession (which implies greater intensity developed by the players) and thereby, gain the benefit of having wildcard players join their team (increase the technical load on each player as the number of ball contacts per player) [10], however, in this study the 4-a-side SSG with wildcard players did show less intensity than the 4-a-side SSG without wildcard players (in terms of HRpeak and SmO ${}_{2}$ ). On the other hand, on recovery periods, the HRaverage, %HRpeak and 85–89% HRpeak was affected by the incorporation of internal wildcard players during SSG, showing a higher value in 4-a-side SSG without wildcard players compared to the same game with wildcard players. This fact might suggest that the SSG without wildcard players are more intense than SSG with wildcard players, and therefore, they might need longer rest intervals.

In terms of muscle oxygenation characteristics (SmO ${}_{2}$ , THb), the evidence available is limited. In a previous study [21], when exercise intensity increased, a decrease in SmO ${}_{2}$ was reported, although the THb did not show variations with changes in exercise intensity. The current results are consistent with those observed in the previous study [21], as SmO ${}_{2}$ decreased more when the exercise intensity was higher (with significant differences in bout 3), such as during the 4-a-side SSG without wildcard players, without changes throughout four bouts nor during recovery periods between the four bouts for both SSG protocols. While THb did not change during both work and rest periods in the SSG protocols, supporting the results of the previous study. These results seem logical, because of HR measurements have showed a negative correlation with the SmO ${}_{2}$ [21], as HR did vary during both work (HRpeak) and rest periods (HRaverage, %HRpeak and 85–89% HRpeak) and, thereby, the SmO ${}_{2}$ values did vary in work period. However, future studies are required to improve the understanding of muscle oxygenation characteristics during SSG protocols.

4.3 Time-motion characteristics

Variations in player number have generally been indicated to affect SSG training intensity [3, 5]. In this study, time-motion characteristics were affected by the introduction of wildcard players. Therefore, this study demonstrated greater total distance travelled, total m/min, distances travelled at higher intensity, number of accelerations in zone 4, maximal speed and average speed during 4-a-side SSG without wildcard players compared to 4-a-side SSG with two internal wildcard players, although no additional differences were observed. This finding is similar to other studies [10, 11] that reported an increase in time-motion characteristics when the SSG was played with equal number of players (i.e., without temporary superiority and inferiority numerical situations). The results of this study suggested that the greater number of players during incorporation of two internal wildcard players caused a reduction of time-motion characteristics to achieve the goal, in this case the maintenance of the ball. This point has a subsequent impact on the physiological response to SSGs tested, which is consistent with previous studies that concluded that increasing the number of players during SSGs decreases the RPE and physiological responses [11, 33] and physical demands [11]. Therefore, if coaches design SSGs with the aim of conditioning, fewer players per team will cause a greater impact at physiological and physical level, regardless of whether the teams are composed of equal numbers or situations of temporary superiority and inferiority.

Finally, some limitations must be addressed. First, the level of players assessed as it could be interesting to examine the response to different SSG formats in male football professional players. Second, the lack of data about women’s response to different SSGs formats and variables.

5. Conclusions

The current article provides preliminary scientific support for the inclusion of internal wildcard players within small-sided games to facilitate the application of the load dynamic throughout the competitive period. From a practical standpoint, the inclusion of internal wildcard players might be well-suited during the competition, on those days of recovery, where the workload should be lower, since the intensity remains high (e.g., HR-related variables) and the volume decreases in terms of external load. This type of small-sided game format let players to train with a high intensity while not causing great fatigue, enabling training or playing a game the next day with maximum performance guarantees. Coaches and technical stuff might find this information very useful in order to accurately know how the inclusion of this variable influences football players from a multidisciplinary (i.e., neuromuscular, physiological and time-motion) approaching.

Author contributions

CONCEPTION: Pascual Bujalance-Moreno, Pedro A. Latorre-Román and Felipe García-Pinillos.

PERFORMANCE OF WORK: Pascual Bujalance-Moreno.

INTERPRETATION OR ANALYSIS OF DATA: Pascual Bujalance-Moreno, Pedro A. Latorre-Román and Felipe García-Pinillos.

PREPARATION OF THE MANUSCRIPT: Pascual Bujalance-Moreno.

REVISION FOR IMPORTANT INTELLECTUAL CONTENT: Pascual Bujalance-Moreno, Rodrigo Ramirez-Campillo, Antonio Martínez-Amat and Felipe García-Pinillos.

SUPERVISION: Pascual Bujalance-Moreno, Pedro A. Latorre-Román and Felipe García-Pinillos.

Ethical considerations

The study was conducted in adherence to the standards of the Declaration of Helsinki (2013 version). The local ethics committee (University of Jaen) approved the informed consent and the study design (reference number: CEHIH 111115, Date: 1/03/2016).

Funding

The authors report no funding.

Footnotes

Acknowledgments

The authors would like to acknowledge the collaboration of Atlético Menciano and C.D. Egabrense.

Conflict of interest

The authors declare that they have no conflict of interest.

References

Eniseler

Şahan

Özcan

Dinler

. High-intensity small-sided games versus repeated sprint training in junior soccer players. J Hum Kinet. 2017; 60(1): 101–11.

Bujalance-Moreno

García-Pinillos

Latorre-Román

. Effects of a small-sided game-based training programme on repeated sprint and change of direction abilities in recreationally-trained football players. J Sports Med Phys Fitness. 2017; 58(7–8): 1021–8.

Bujalance-Moreno

Latorre-Román

PÁ

García-Pinillos

. A systematic review on small-sided games in football players: acute and chronic adaptations. J Sports Sci. 2018; 0414(00): 1–29.

Bompa

. Theory and methodology of training. Kendall/Hunt Publ Co. 1983.

Hill-Haas

Dawson

Impellizzeri

Coutts

. Physiology of small-sided games training in football: a systematic review. Sport Med. 2011; 41(3): 199–220.

Impellizzeri

Marcora

Castagna

Reilly

Sassi

Laia

Rampinini

. Physiological and performance effects of generic versus specific aerobic training in soccer players. Int J Sports Med. 2006; 27(6): 483–92.

Brandes

Heitmann

Müller

. Physical responses of different small-sided game formats in elite youth soccer players. J Strength Cond Res. 2012; 26(5): 1353–60.

Aslan

. Cardiovascular responses, perceived exertion and technical actions during small-sided recreational soccer: effects of pitch size and number of players. J Hum Kinet. 2013 Jan 1; 38: 95–105.

Sanchez-Sanchez

Hernández

Casamichana

Martínez-Salazar

Ramirez-Campillo

Sampaio

. Heart rate, technical performance, and session-RPE in elite youth soccer small-sided games played with wildcard player. J Strength Cond Res. 2017; 31(10): 2678–85.

10.

Hill-Haas

Coutts

Dawson

Rowsell

. Time-motion characteristics and physiological responses of small-sided games in elite youth players: the influence of player number and rule changes. J Strength Cond Res. 2010; 24(8): 2149–56.

11.

Torres-Ronda

Gonçalves

Marcelino

Torrents

Vicente

Sampaio

. Heart rate, time-motion, and body impacts when changing the number of teammates and opponents in soccer small-sided games. J Strength Cond Res. 2015; 29(10): 2723–30.

12.

Evangelos

Eleftherios

Aris

Ioannis

Konstantinos

Natalia

. Supernumerary in small sided games 3vs3 & 4vs4. J Phys Educ Sport. 2012; 12(3): 398–406.

13.

Maio Alves

Rebelo

Abrantes

Sampaio

. Short-term effects of complex and contrast training in soccer players’ vertical jump, sprint, and agility abilities. J strength Cond Res. 2010; 24(4): 936–41.

14.

Lehance

Binet

Bury

Croisier

. Muscular strength, functional performances and injury risk in professional and junior elite soccer players. Scand J Med Sci Sports. 2009 Mar 31; 19(2): 243–51.

15.

Rago

Brito

Figueiredo

Carvalho

Fernandes

Fonseca

Rebelo

. Countermovement jump analysis using different portable devices: implications for field testing. Sports. 2018; 6(3): 91.

16.

Spurrs

Murphy

Watsford

. The effect of plyometric training on distance running performance. Eur J Appl Physiol. 2003; 89(1): 1–7.

17.

Ramirez-Campillo

Andrade

Izquierdo

. Effects of plyometric training volume and training surface on explosive strength. J Strength Cond Res. 2013; 27(10): 2714–22.

18.

Borg

. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med. 1970; 2: 92–8.

19.

Tanaka

Monahan

Seals

. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001 Jan 1; 37(1): 153–6.

20.

Casamichana

Castellano

. Time-motion, heart rate, perceptual and motor behaviour demands in small-sides soccer games: effects of pitch size. J Sports Sci. 2010 Dec 11; 28(14): 1615–23.

21.

Crum

O’Connor

Van Loo

Valckx

Stannard

. Validity and reliability of the Moxy oxygen monitor during incremental cycling exercise. Eur J Sport Sci. 2017; 17(8): 1037–43.

22.

Bastida Castillo

Gómez Carmona

De la CruzSánchez

Pino Ortega

. Accuracy, intra- and inter-unit reliability, and comparison between GPS and UWB-based position-tracking systems used for time-motion analyses in soccer. Eur J Sport Sci. 2018; 1–8.

23.

Casamichana

Suarez-Arrones

Castellano

San Román-Quintana

. Effect of number of touches and exercise duration on the kinematic profile and heart rate response during small-sided games in soccer. J Hum Kinet. 2014; 41: 113–23.

24.

Hill-Haas

Dawson

Coutts

Rowsell

. Physiological responses and time-motion characteristics of various small-sided soccer games in youth players. J Sports Sci. 2009; 27(1): 1–8.

25.

Dellal

Owen

Wong

Krustrup

Van Exsel

Mallo

. Technical and physical demands of small vs. large sided games in relation to playing position in elite soccer. Hum Mov Sci. 2012; 31: 957–69.

26.

Clemente

Nikolaidis

Van Der Linden

CMIN

Silva

. Effects of small-sided soccer games on internal and external load and lower limb power: a pilot study in collegiate players. Hum Mov. 2017; 18(1): 50–7.

27.

Katis

Kellis

. Effects of small-sided games on physical conditioning and performance in young soccer players. J Sport Sci Med. 2009; 8(3): 374–80.

28.

Delecluse

. Influence of strength training on sprint running performance. Sport Med. 1997 Sep; 24(3): 147–56.

29.

Buchheit

. Performance and physiological responses to repeated-sprint and jump sequences. Eur J Appl Physiol. 2010; 110(5): 1007–18.

30.

Köklü

Aşçi

Koçak

FÜ

Alemdaroğlu

Dündar

. Comparison of the physiological responses to different small-sided games in elite young soccer players. J Strength Cond Res. 2011 Jun; 25(6): 1522–8.

31.

Clemente

Dellal

Wong

Lourenço Martins

Mendes

. Heart rate responses and distance coverage during 1 vs. 1 duel in soccer: effects of neutral player and different task conditions. Sci Sports. 2016; 31(5): e155–61.

32.

Halouani

Chtourou

Gabbett

Chaouachi

Chamari

. Small-sided games in team sports training: a brief review. J Strength Cond Res. 2014; 28(12): 3594–618.

33.

Abrantes

Nunes

MaÇãs

Leite

Sampaio

. Effects of the number of players and game type constraints on heart rate, rating of perceived exertion, and technical actions of small-sided soccer games. J Strength Cond Res. 2012; 26(4): 976–81.

The inclusion of wildcard players during small-sided games causes alterations on players’ workload

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Methods

2.1 Participants

2.2 Experimental approach to the problem

2.3 Procedures

2.4.1 20-m sprint

2.4.2 Countermovement vertical jump (CMJ)

2.4.3 Rating of perceived exertion (RPE)

Table 1 Physical fitness comparison (Mean ± SD) between two different formats of small-sided games in amateur soccer players ( n = 16)

2.4.5 Muscle oxygen saturation (SmO 2 ) and total muscle haemoglobin (THb)

2.4.6 Time-motion characteristics

2.5 Statistical analysis

3. Results

3.1 Physical fitness assessment

Table 2 Physiological and perceptual responses comparison (Mean ± SD) between two different formats of small-sided games in amateur football players on bout periods ( n = 16)

3.3 Time-motion characteristics

Table 4 Time-motion characteristics comparison (Mean ± SD) between two different formats of small-sided games in amateur football players on bout periods ( n = 16)

4.1 Physical fitness performance

4.2 Physiological and perceptual characteristics

4.3 Time-motion characteristics

5. Conclusions

Author contributions

Ethical considerations

Funding

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Physical fitness comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur soccer players ( $n=$ 16)

2.4.5 Muscle oxygen saturation (SmO ${}_{2}$ ) and total muscle haemoglobin (THb)

Table 2
Physiological and perceptual responses comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur football players on bout periods ( $n=$ 16)

Table 4
Time-motion characteristics comparison (Mean $\pm$ SD) between two different formats of small-sided games in amateur football players on bout periods ( $n=$ 16)