International  Journal  of
Environmental Research
and Public Health
Article
Variations of Internal and External Load Variables
between Intermittent Small-Sided Soccer Game
Training Regimens
Filipe Manuel Clemente 1,2
, Pantelis Theodoros Nikolaidis 3
, Thomas Rosemann 4 and
Beat Knechtle 4,5,*
1
School of Sport and Leisure, Polytechnic Institute of Viana do Castelo, 4960-320 Melgaço, Portugal
2
Instituto de Telecomunicações, Delegação da Covilhã, 6200-001 Covilha, Portugal
3
Exercise Physiology Laboratory, 18450 Nikaia, Greece
4
Institute of Primary Care, University of Zurich, 8091 Zurich, Switzerland
5
Medbase St. Gallen Am Vadianplatz, 9001 St. Gallen, Switzerland
*
Correspondence: beat.knechtle@hispeed.ch; Tel.: +41-(0)-71-226-9300
Received: 24 July 2019; Accepted: 13 August 2019; Published: 15 August 2019


Abstract: The purpose of this study was twofold: (i) analyze the variations of internal and external
load between intermittent regimens (6 × 3’ and 3 × 6’) during a small-sided game (SSG); and (ii)
analyze the variations of internal and external load within-intermittent regimens (between sets). Ten
male amateur soccer players (age: 21.7 ± 2.1 years) participated in this study. Almost certain large
decreases in total distance (−8.6%, [−12.3; −4.8], Eﬀect Size (ES): −1.51, [−2.20; −0.82]) and running
distance (−34.0%, [47.0; −17.8], ES: −2.23, [−3.40; −1.05]) were observed when comparing the 3 × 6’
and 6 × 3’. Very likely moderate and large decreases in total accelerations (−24.0%, [−35.1; −10.9];
ES: −1.11, [−1.75; −0.47]) and total of decelerations (−26.7%, [−38.8; −12.1]; ES:−1.49, [−2.36; −0.62]),
respectively, were found when comparing the 3 × 6’ and 6 × 3’. Very likely increases in rated of
perceived exertion in the set 3 in comparison to the 1st during the 3 × 6’ SSG (34.5%, [12.4; 61.0], ES:
1.35, [0.53; 2.16]) and the 6 × 3’ (29.9%, [11.6; 51.2]; ES: 1.17, [0.49; 1.85]). Longer sets increase the
perception of eﬀort and contribute to a large decrease in total and running distances, and total of
accelerations and decelerations. Meaningful decreases in time-motion demands occur between sets
2 and 3 while perceived eﬀort increases.
Keywords: association football; drill-based tasks; intermittent exercises; physiological; physical;
performance
1. Introduction
Small-sided games (SSGs) are very popular exercise drills designed by coaches to replicate
oﬃcial match dynamics and increase the intensity and individual participation of players during
soccer training sessions [1,2]. In SSGs, the format of play (number of players involved), pitch size,
and some rules can be manipulated to adjust the exertion required by players to meet the coach’s
proposed objective [3,4]. One of the advantages of SSGs is that, if properly designed, they may
represent an eﬀective strategy for multicomponent training [5], allowing for the development of both
physical/physiological and technical/tactical skills at the same time [6].
SSGs are often used to promote new aﬀordances and to adjust the tactical complexity to the main
goal of the coach, improving the decision making of players [7]. In fact, small variations in these
games may promote a signiﬁcant change in the player’s behavior, thus resulting in consequences for
the overall intensity of exercise [8]. Despite these games being promoted for improving the collective
Int. J. Environ. Res. Public Health 2019, 16, 2923; doi:10.3390/ijerph16162923
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and individual behavior of players, there is also a relationship with the physical and physiological
demands of players.
Among the common topics researched in SSGs and its physiological eﬀects is the eﬀects of training
regimens on players’ performance and acute responses [9]. The load imposed on players and the way
in which this load occurs must be understood to ensure that training stimuli are adjusted to promote
high-intensity exertion without compromising external load or technical/tactical performance [10].
The load is closely related to the following training prescription that should be taken in account [2]:
(a) work intensity and duration; (b) recovery type (rest/active recovery) and duration; and (c) total
work duration (work interval number × work duration).
In the speciﬁc case of SSGs, comparisons between continuous and intermittent training regimens
are commonly conducted [9,11]. Most results do not reveal meaningful or clear changes between these
types of regimens in terms of heart rate responses and blood lactate concentrations [9,12]. However,
when comparing diﬀerent intermittent regimens (short, moderate, and long) with continuous regimens,
the evidence suggests that continuous regimens result in higher values of maximal heart rate, blood
lactate concentration, and perceived exertion [13]. Moreover, continuous regimens seem to increase
the distance covered at low running speeds and decrease moderate-to-intense running distances [13].
As high-intensity drills, SSGs seem to ﬁt in the category of interval training. Rather than compare
the acute eﬀects of continuous versus intermittent regimens, it is important to analyze the eﬀects of
diﬀerent intermittent regimens. In a study conducted using a 3 × 3 SSG format, it was found that
long bouts (sets) (3 × 6 min/2 min rest) decreased heart rate responses in comparison to medium
(3 × 4 min/2 min rest) and small (3 × 2 min/2 min rest) bouts [14] if the ﬁrst minute of data is excluded.
However, no meaningful changes were observed in perceived exertion or technical actions [14]. In
another study, it was found that, compared to long bouts, shorter bouts elicited lower maximal heart
rate, shorter total distance covered at low running speed, and greater distances covered at medium
and high running speeds [13].
The proper adjustment of SSGs to suit the purpose of training may help coaches optimize the
amount of exertion imposed on players and may improve their performance. However, while a couple
of experiments have compared diﬀerent intermittent soccer training regimens [13,14], the information
presented lacks a clear demonstration of the eﬀects of diﬀerent training regimens on internal (acute
physiological responses) and external (physical demands) load variables. A comparison between
bout durations should help researchers understand the patterns of exertion and provide meaningful
information to coaches to help them choose the most eﬀective regimens for their players. Moreover,
coaches will also be able to analyze the eﬀects of diﬀerent intermittent regimens on time-motion
performance during SSGs. Based on this rationale, the aim of the present study was two-fold: (i) to
analyze variations in rate of perceived exertion, heart rate responses, and time-motion demands
between two intermittent training regimens (6 × 3’ and 3 × 6’) during an SSG (5 × 5 format); and (ii) to
test the variations of the above-mentioned variables within training regimens (between sets).
2. Materials and Methods
2.1. Participants
Ten male amateur soccer players (age: 23.7 ± 1.1 years; experience: 10.3 ± 3.1 years; height:
178.2 ± 5.3 cm; weight: 72.1 ± 4.9 kg) competing at the regional level participated in this study. The
participants usually trained three times a week and played one match every week. Participants were
informed about the study design and the potential implications, risks, and beneﬁts of participating.
After that, participants freely signed an informed consent. The experiment followed the ethical
standards of the Declaration of Helsinki for the study in humans. The study was approved by the local
ethical committee (School of Sport and Leisure) with the code number IPVC-ESDL180503.
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2.2. Experimental Approach
This study used a counterbalanced repeated-measures design to compare the rate of perceived
exertion (RPE), mean heart rate (HRmean), total distance (TD), running distance (RD), sprinting distance
(SD), total accelerations (TAc), total decelerations (TDc) and player load (PL) of the participants in two
diﬀerent SSG regimens: 6 sets of 3 min with 2 min of rest (6 × 3’ regimen) and 3 sets of 6 min with
2 min of rest (3 × 6’ regimen). The study was conducted for 2 weeks immediately after the last oﬃcial
match of the season. The study occurred in the same pitch and the 10 players participated in all data
collection sessions.
The 5 × 5 format was employed in both training regimens. Each regimen was implemented twice,
interspaced by a period of one week to ensure each session was performed under similar conditions.
In each session, only one SSG regimen was implemented. In the ﬁrst week, the 6 × 3’ regimen was
implemented ﬁrst and the 3 × 6’ regimen was implemented 48 h afterward, without any other training
sessions in between. In the second week, the inverse sequence was employed. The mean of results
obtained in each condition (mean of the two days of data collection with the same regimen) was used
between regimens comparisons.
The players were distributed into two teams based on skill level and playing position to homogenize
the competitive level. The teams did not change during the study. Players wore vests equipped with
a GPS and HR sensors during the SSGs. The SSGs were played on synthetic turf at 6:00 p.m. at an
average temperature of 23 ◦C and a relative humidity of 57% no SSGs played under rainy weather
conditions. All SSGs were preceded by a standardized warm-up consisting of 5 min of jogging, 5 min
of lower-limb dynamic stretching and mobility exercises, 5 min of agility and speed drills, and 5 min of
a ball possession game.
2.3. Small-Sided Game
The 5 × 5 format was implemented with small goals (2 × 1 m) without goalkeepers. The size of
the pitch was 42 × 22 m (924 m2). The individual playing area (area divided by the total number of
players) followed previous recommendations to promote SSGs based on the real game situations (area
of play) in attacking processes [15]. Two training regimens were used: 6 × 3’/2’ rest and 3 × 6’/2’ rest.
The teams were composed of 2 defenders, 2 midﬁelders and 1 forward with similar skill levels as based
on a preliminary observational test.
No speciﬁc verbal instructions were provided before, during, or after the SSGs. However, verbal
encouragement was provided to keep players committed and to help them to maintain a high exertion
level. Six balls were placed around the pitch to ensure a quick repositioning if the ball in play went out
of bounds. The SSGs followed oﬃcial soccer rules with exception of oﬀside.
2.4. Rating of Perceived Exertion (RPE)
Players were instructed to rate their perceived eﬀort immediately after each SSG. The CR-10 point
scale [16] was used to classify the eﬀort; on this scale, 1 means “very light activity” and 10 means
“maximal exertion.” Players rated the eﬀort individually as to not hear or be inﬂuenced by other
teammates’ responses. All the players were previously instructed of the use of the scale to optimize
the accuracy of their ratings during the experiments.
2.5. Heart Rate (HR) and Global Positioning System (GPS)
Players wore an HR sensor and a chest belt (Polar H7, Polar Electro, OY, Kempele, Finland) which
recorded data every second during the SSGs. Data were imported into the Polar Team application. The
HRmean (bpm) per each set was used to measure this variable.
The players also wore a vest with a geolocation tracker (JOHAN Sports, Noordwijk, The
Netherlands) consisting of a GPS sensor (10 Hz, including EGNOS correction), accelerometer, gyroscope,
and magnetometer (100 Hz, 3 axes). The validity and reliability values of the devices can be found in a
Int. J. Environ. Res. Public Health 2019, 16, 2923
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previous study [17]. The tracker was placed in a bag of the vest located at the dorsal region. The data
was exported and treated immediately after each session.
The following variables were collected from the tracker devices: (a) total distance (meters per
minute); (b) running distance at 14–19.9 km/h (meters per minute); (c) sprinting distance at >20.0 km/h
(meters per minute); (d) total accelerations >2 m/s2 (number per minute); (e) total decelerations >2 m/s2
(number per minute); and (f) player’s load (g per min), being calculated by estimating the total
acceleration diﬀerence between two consecutive time steps being the length of the three-dimensional
vector of accelerations in the anteroposterior, mediolateral, and craniocaudal axes between time step = 0
and time step = 1. Players were familiarized with the use of the HR belts and trackers vests before the
study began.
2.6. Statistical Procedures
The results are presented as either means and standard deviations (SD) or percentage diﬀerences
and 90% conﬁdence intervals (90% CI). The conﬁdence intervals were deﬁned following the
recommendations for this kind of sample [18]. Normality and homogeneity of the data were ﬁrstly
tested and veriﬁed before the inference analyses. Between-training regimens and within-training
regimens diﬀerences were analyzed using the standardized diﬀerences of the eﬀect size (ES) [19],
with a 90% CI. ES was classiﬁed as trivial (<0.2), small (0.2–0.6), moderate (0.6–1.2), or large
(>1.2) [18]. Probabilities were calculated considering the smallest worthwhile changes (SWC, 0.2 ×
between-subjects SD) [20]. Qualitative probabilistic mechanistic inferences of the true eﬀects were made
using these probabilities [20]. The scale for qualitative probabilities was as follows: 25–75% = possible;
75–95% = likely; 95–99% = very likely; >99% = almost certain [20].
3. Results
Descriptive statistics of internal and external load variables in both SSG training regimens can be
found in Table 1 (values represent the average of the two sessions per type of intermittent protocol).
Descriptive analyses reveal that RPE were higher in the last set in both 6 × 3’ (6.1 ± 1.9 arbitrary
units (A.U.)) and 3 × 6’ (6.7 ± 1.6 A.U.) training regimens. The HRmean was higher in the second
set of 6 × 3’ regimen (171.6 ± 10.0 bpm) and in the third set of 3 × 6’ regimen (171.1 ± 10.9). TD was
greater in the third set of 6 × 3’ regimen (112.5 ± 11.1 m/min) and in the ﬁrst set of 3 × 6’ regimen
(103.3 ± 7.6 m/min). RD was greater in the second set of 6 × 3’ regimen (10.0 ± 5.1 m/min) and in
the second set of 3 × 6’regimen (9.4 ± 5.6 m/min). SD was greater in the third set of 6 × 3’ regimen
(1.5 ± 1.9 m/min) and in the second set of 3 × 6’ regimen (0.7 ± 1.3 m/min). TAc and TDc were greater
in the second set of 6 × 3’ regimen (2.9 ± 0.8 and 2.7 ± 0.9 n/min, respectively) and in the ﬁrst set of
3 × 6’ regimen (2.1 ± 1.0 and 1.9 ± 1.0 n/min, respectively). Finally, PL was greater in the second and
third sets of 6 × 3’ regimen (7.3 ± 1.3 g/min) and in the ﬁrst set of 3 × 6’ regimen (1.9 ± 1.0 g/min).
Between-training regimen variations can be found in Table 2 (values represent the average of
the two sessions per type of intermittent protocol). Almost certain large decreases of TD (−8.6%,
[−12.3; −4.8], ES: −1.51, [−2.20; −0.82]) and RD (−34.0%, [47.0; −17.8], ES: −2.23, [−3.40; −1.05]) were
observed when comparing 3 × 6’ versus 6 × 3’ regimens. Very likely moderate and large decreases
of TAc (−24.0%, [−35.1; −10.9]; ES: −1.11, [−1.75; −0.47]) and TDc (−26.7%, [−38.8; −12.1]; ES: −1.49,
[−2.36; −0.62]), respectively, were found when comparing 3 × 6’ versus 6 × 3’ regimens.
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Table 1. Descriptive statistics (Mean (Standard Deviation)) of internal and external load during the SSGs.
Variable
6 × 3’ Regimen
3 × 6’Regimen
S1
S2
S3
S4
S5
S6
S1
S2
S3
RPE (A.U.)
4.2 (1.5)
4.9 (1.3)
5.6 (1.4)
6.0 (1.3)
5.9 (1.3)
6.1 (1.9)
5.0 (1.2)
6.3 (1.1)
6.7 (1.6)
HRmean (bpm)
170.9 (11.1)
171.6 (10.0)
169.8 (10.9)
170.2 (12.5)
166.3 (10.8)
165.2 (12.4)
169.1 (11.7)
168.8 (10.5)
171.1 (10.9)
TD (m/min)
107.7 (10.2)
111.7 (9.1)
112.5 (11.1)
106.8 (9.8)
104.1 (8.8)
101.6 (10.9)
103.3 (7.6)
99.8 (6.9)
90.9 (15.6)
RD (m/min)
10.0 (5.1)
14.1 (5.7)
12.8(4.7)
10.6 (5.2)
11.1 (5.6)
9.1 (6.6)
8.7 (5.5)
9.4 (5.6)
6.0 (3.8)
SD (m/min)
0.5 (1.1)
1.0 (1.6)
1.5 (1.9)
0.7 (1.2)
1.0 (1.6)
0.3 (0.7)
0.6 (0.9)
0.7 (1.3)
0.5 (0.8)
TAc (n/min)
2.7 (0.9)
2.8 (0.6)
2.9 (0.8)
2.2 (1.0)
2.2 (1.0)
2.4 (1.2)
2.1 (1.0)
1.8 (0.9)
1.9 (1.1)
TDc (n/min)
2.4 (1.1)
2.5 (0.6)
2.7 (0.9)
1.7 (0.9)
2.1 (1.0)
2.1 (1.2)
1.9 (1.0)
1.7 (0.9)
1.6 (0.9)
PL (g/min)
7.2 (1.2)
7.3 (1.3)
7.3 (1.3)
6.8 (1.3)
6.4 (1.1)
6.5 (1.1)
6.9 (0.9)
6.3 (0.8)
5.9 (1.3)
SSGs: small-sided games. RPE: rated of perceived exertion (CR-10 scale); HRmean: mean heart rate; TD: total distance; RD: running distance; SD: sprinting distance; TAc: total accelerations;
TDc: total decelerations; PL: player’s load; S: set; A.U.: arbitrary units; bpm: beats per minute; m/min: meters per minute; n/min: number per minute: g/min: g per minute.
Table 2. Comparison of internal and external load variables between training regimens in terms of percentage and standardized diﬀerences and the probabilities of
each standardized diﬀerence.
Variable
M (SD)
3 × 6’ Reg.
M (SD)
6 × 3’ Reg.
% Diﬀerence
(3 × 6’ Reg.–6 × 3’ Reg.)
Standardized Diﬀerence
(3 × 6’ Reg.–6 × 3’ Reg.)
% Greater/Similar/Lower Values
for 3 × 6’ Reg. vs. 6 × 3’ Reg.
Value
[90% CI]
Value
(Magnitude)
90% CI
RPE (A.U.)
5.97 (0.80)
5.43 (0.91)
10.7
[2.9; 19.2]
0.49 small
[0.14; 0.84]
92/8/0 Likely
HRmean (bpm)
169.67 (10.05)
169.52 (9.75)
0.1
[−1.8; 2.0]
0.01 trivial
[−0.28; 0.31]
14/75/11 Unclear
TD (m/min)
98.39 (7.49)
107.56 (5.99)
−8.6
[−12.3; −4.8]
−1.51 large
[−2.20; −0.82]
0/0/100 Almost certain
RD (m/min)
8.04 (3.31)
11.28 (1.87)
−34.0
[−47.0; −17.8]
−2.23 large
[−3.40; −1.05]
0/0/100 Almost certain
SD (m/min)
0.62 (0.42)
0.83 (0.49)
−13.9
[−46.7; 39.3]
−0.13 trivial
[−0.54; 0.29]
9/53/38 Unclear
TAc (n/min)
1.95 (0.55)
2.53 (0.54)
−24.0
[−35.1; −10.9]
−1.11 moderate
[−1.75; −0.47]
0/1/99 Very likely
TDc (n/min)
1.70 (0.53)
2.24 (0.39)
−26.7
[−38.8; −12.1]
−1.49 large
[−2.36; −0.62]
0/1/99 Very likely
PL (g/min)
6.37 (0.79)
6.92 (0.99)
−7.8
[−12.6; −2.7]
−0.58 small
[−0.97; −0.20]
0/5/95 Likely
RPE: rated of perceived exertion (CR-10 scale); HRmean: mean heart rate; TD: total distance; RD: running distance; SD: sprinting distance; TAc: total accelerations (>2 m/s2); TDc: total
decelerations (>2 m/s2); PL: g/min; S: set; Reg.: training regimen; A.U.: arbitrary units; bpm: beats per minute; m/min: meters per minute; n/min: number per minute: g/min: g per minute.
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Within-training regimen diﬀerences can be found in Figures 1 and 2. To simplify the analysis, the
six sets within 6 × 3’ SSG regimen were grouped in three sets consisting the ﬁrst set in the average of
sets 1 and 2, the second set in the average of sets 3 and 4 and the third set in the average of 5 and 6.
Very likely increases of RPE were found in the 3rd set in comparison to the 1st during the 3 × 6’ SSG
regimen (34.5%, [12.4; 61.0], ES: 1.35, [0.53; 2.16], large magnitude) and 6 × 3’ SSG regimen (29.9%, [11.6;
51.2]; ES: 1.17, [0.49; 1.85], moderate magnitude). Trivial-to-small changes of HR were found between
sets in both training regimens. Likely decreases of total distance were found from set 3 to set 1 (−11.6%,
[−20.8; −1.3], ES: −1.78, [−3.38; −0.19], large magnitude) and from set 2 to set 3 (−9.2%, [−18.6; 1.3], ES:
−1.33, [−2.85; 0.18], large magnitude) in 3 × 6’ SSG regimen. Very likely decreases of total distance
were found from set 3 to set 1 (−6.2%, [−8.8; −3.5], ES: −0.96, [−1.39; −0.53], moderate magnitude) and
almost certain decreases were found from set 3 to set 2 (−6.0%, [−8.0; −3.9], ES:−0.87, [−1.18; −0.56],
moderate magnitude) in 6 × 3’ SSG regimen. Very likely decreases of player load were found from set
3 to set 1 (−13.1%, [−23.1; −2.9], ES: −1.37, [−2.46; −0.27], large magnitude] during 3 × 6’ SSG regimen.
Int. J. Environ. Res. Public Health 2019, 16, x 
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(a) 
(b) 
 
 
(c) 
(d) 
Figure 1. Standardized difference (Cohen) between sets in (a) RPE; (b) HRmean; (c) Total Distance; 
and (d) Player Load. The six sets of the 6 × 3’ regimen were grouped in three sets (S1: mean of set 1 
and 2; S2: mean of set 3 and 4; S3: mean of set 5 and 6) to a better visualization and analysis. 
Standardized value direction depends on the relationship A-B. 
Figure 1. Standardized diﬀerence (Cohen) between sets in (a) RPE; (b) HRmean; (c) Total Distance; and
(d) Player Load. The six sets of the 6 × 3’ regimen were grouped in three sets (S1: mean of set 1 and 2;
S2: mean of set 3 and 4; S3: mean of set 5 and 6) to a better visualization and analysis. Standardized
value direction depends on the relationship A-B.
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Figure 1. Standardized difference (Cohen) between sets in (a) RPE; (b) HRmean; (c) Total Distance; 
and (d) Player Load. The six sets of the 6 × 3’ regimen were grouped in three sets (S1: mean of set 1 
and 2; S2: mean of set 3 and 4; S3: mean of set 5 and 6) to a better visualization and analysis. 
Standardized value direction depends on the relationship A-B. 
 
 
(a) 
(b) 
Int. J. Environ. Res. Public Health 2019, 16, x 
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(c) 
(d) 
Figure 2. Standardized difference (Cohen) between sets in (a) running distance; (b) sprinting distance; 
(c) total accelerations; and (d) total decelerations. The six sets of the 6 × 3’ regimen were grouped in 
three sets (S1: mean of set 1 and 2; S2: mean of set 3 and 4; S3: mean of set 5 and 6) to a better 
visualization and analysis. Standardized value direction depends on the relationship A-B. 
Within-training regimens differences in running distance were trivial-to-small in the majority of 
comparisons and the moderate magnitudes were unclear. Considering the sprinting distances, the 
variations were also trivial-to-small. Unclear large (−30.6%, [−58.3; 15.5], ES: −1.96, [−4.69; 0.77], large 
magnitude) and unclear moderate (−24.9%, [−52.3; 18.7], ES: −1.18, [−3.08; 0.71], moderate magnitude) 
decreases of total accelerations were found from set 3 to set 1 and set 3 to set 2 during 6 × 3’ SSG 
regimen, respectively. Trivial-to-small changes of total decelerations and unclear moderate 
differences were found in both training regimens. 
4. Discussion 
Between-SSG training regimens, changes were observed in the present study. Almost certain 
large increases in total and running distances were observed in the shorter sets (6 × 3’), and very likely 
moderate and large increases in total accelerations and decelerations, respectively, during shorter 
sets were found. RPE showed likely small increases during longer sets (6 × 3’). Likely small increases 
in player load during shorter sets were also found. Briefly, this evidence suggests that shorter sets 
contribute to an increase in terms of moderate-running speed distances and high-intensity actions 
associated with accelerations and decelerations higher than 2 m/s2 while resulting in a lower RPE than 
in longer sets. Although no meaningful differences were found in a study that compared time-motion 
variables between 4 × 4’ and 2 × 8’ 5 × 5 SSG regimens [11], our results are partially in line with the 
findings of a study that compared short (6 × 2’), medium (3 × 4’), and long (2 × 6’) regimens [13]. 
Heart rate responses were trivially different between regimens, suggesting that this variable is 
not sensitive to variations in the intermittent regimens tested in our study. These results are in line 
with previous studies that compared heart rate responses after different intermittent regimens 
[11 14] Ho
e e
the alte
ati e i te
al load
a ke u ed i
ou
tudy (RPE) e ealed a likely
all
Figure 2. Standardized diﬀerence (Cohen) between sets in (a) running distance; (b) sprinting distance;
(c) total accelerations; and (d) total decelerations. The six sets of the 6 × 3’ regimen were grouped
in three sets (S1: mean of set 1 and 2; S2: mean of set 3 and 4; S3: mean of set 5 and 6) to a better
visualization and analysis. Standardized value direction depends on the relationship A-B.
Within-training regimens diﬀerences in running distance were trivial-to-small in the majority of
comparisons and the moderate magnitudes were unclear. Considering the sprinting distances, the
variations were also trivial-to-small. Unclear large (−30.6%, [−58.3; 15.5], ES: −1.96, [−4.69; 0.77], large
magnitude) and unclear moderate (−24.9%, [−52.3; 18.7], ES: −1.18, [−3.08; 0.71], moderate magnitude)
decreases of total accelerations were found from set 3 to set 1 and set 3 to set 2 during 6 × 3’ SSG
regimen, respectively. Trivial-to-small changes of total decelerations and unclear moderate diﬀerences
were found in both training regimens.
4. Discussion
Between-SSG training regimens, changes were observed in the present study. Almost certain
large increases in total and running distances were observed in the shorter sets (6 × 3’), and very likely
moderate and large increases in total accelerations and decelerations, respectively, during shorter sets
were found. RPE showed likely small increases during longer sets (6 × 3’). Likely small increases
in player load during shorter sets were also found. Brieﬂy, this evidence suggests that shorter sets
contribute to an increase in terms of moderate-running speed distances and high-intensity actions
associated with accelerations and decelerations higher than 2 m/s2 while resulting in a lower RPE than
in longer sets. Although no meaningful diﬀerences were found in a study that compared time-motion
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variables between 4 × 4’ and 2 × 8’ 5 × 5 SSG regimens [11], our results are partially in line with the
ﬁndings of a study that compared short (6 × 2’), medium (3 × 4’), and long (2 × 6’) regimens [13].
Heart rate responses were trivially diﬀerent between regimens, suggesting that this variable is
not sensitive to variations in the intermittent regimens tested in our study. These results are in line
with previous studies that compared heart rate responses after diﬀerent intermittent regimens [11,14].
However, the alternative internal load marker used in our study (RPE) revealed a likely small increase
during longer sets, suggesting that raising RPE may compromise the consistency of physical demands
across sets.
Comparisons within SSG regimens were also performed to analyze the variations between sets.
Main variations were found in RPE, total and running distances, and player load. Intriguingly,
higher-intensity physical demands (sprinting distance and total accelerations and decelerations) were
relatively constant across sets.
Moderate and progressive increases in RPE were found across sets, mainly during the 3 × 6’
regimen. The progressive increase in RPE scores was also found during shorter bouts. Trivial-to-small
diﬀerences were found between the third and second sets. Eventually, longer sets may contribute to a
perceptual increase of eﬀort [21]. However, the fatigue eﬀect may be the cause of such RPE increases,
especially considering that decreases in total and running distances and player load occurred across
the sets in both regimens.
Despite these progressive decreases, it was observed that shorter sets are probably more beneﬁcial
to delaying the impact of fatigue on total distance because large decreases were found between sets 1
and 3 and between sets 2 and 3 during the 3 × 6’ regimens, and only moderate eﬀects were found during
the 6 × 3’ regimens. Similar evidence was found regarding running distance. Moderate decreases were
found across the sets during longer sets, and only small diﬀerences were observed during shorter sets.
In both regimens and for both variables (total and running distance) trivial-to-small decreases were
found from set 1 to set 2, suggesting that the main eﬀects of fatigue emerge from the continuity of
exertion [22].
The greater constancy of results in terms of sprinting distance and total of accelerations and
decelerations across the sets may suggest that the resting period of 2 min was enough to maintain
intensity levels and to maximize energy phosphates as the primary energy source [23]. However, in
the speciﬁc case of sprinting distance, the values per minute did not reach 1 m on average; thus, the
constancy can also be justiﬁed by the low frequency of these demands across the 5 × 5 format.
Interestingly, knowledge about the period of time may also constrain the pace of players during
the games. In fact, a previous study that compared diﬀerent intermittent regimens and their eﬀects
on pacing revealed that high-speed distances progressively and largely decreased across shorter sets
(1 min) based on the ‘all-out’ pacing strategy used by rugby players [22]. Conversely, during longer
sets, a more constant high-speed pace across the sets was observed [22]. The results of the present are
in line with these previous ﬁndings. However, this constancy in the most intense activities that occurs
in longer sets also resulted in smaller values when compared with shorter sets.
Our study had some limitations. The number and the competitive level of the players may
constrain the inferences of this study. Theoretically, professional players present greater aerobic and
anaerobic capacities, thus making it possible to reduce the magnitude of decreases throughout the
bouts. However, the main results are in line with those of previous studies conducted in elite youth
players [13], amateurs [11], and professionals [14]. In addition, our study analyzed the eﬀects in only
one SSG format, and for that reason, the occurrences of sprinting distances are scarce. Bigger formats
should be considered for testing variations between regimens. Diﬀerent work-to-rest ratios should be
considered in future study designs in order to analyze the eﬀects of rest on physical demands and
the internal eﬀect of the exercise. In fact, in our study the diﬀerence between training regimen also
constrained the time of recovery and the work-to-rest ratios were diﬀerent between regimens, thus
this may interfere with some generalizations that can be made from our study. The small number of
participants should also be considered as a limitation for a possible generalization of the evidence.
Int. J. Environ. Res. Public Health 2019, 16, 2923
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Other conditions should also be understood as contextual and for that reason may aﬀect comparisons
with future studies, namely: (i) the synthetic grass was not wet; (ii) the same study conducted in
another period of the season may conduct to diﬀerent evidence; (iii) possibly more sessions would
lead to a better copy with the decrements throughout the bouts; and (iv) diﬀerent task conditions that
aﬀect the player’s behavior and, consequently, the intensity of exercise [24].
Despite these limitations, this study revealed that diﬀerent training regimens led to diﬀerent
eﬀects on internal and external load variables. The main highlights of the present study are that shorter
sets (3’) seem to be more beneﬁcial than longer sets (6’) in keeping total and running distances and
total accelerations and decelerations constant while decreasing the RPE. Additionally, the greater
decrements seem to mostly occur in the last sets. Despite the somewhat predictable results, the
small amount of previous research into such speciﬁc issues highlights the innovative character of the
present study to reveal that shorter sets contribute to a greater external load stimulus despite that no
meaningful changes were found between training regimens in the internal load. This may suggest that
the internal load measures cannot be the unique criteria to choose between bout periods. In fact, in the
present study it is possible to observe that despite the similarity of internal load between intermittent
regimens, meaningful increases of some important external load measures were found (e.g., total
distance, running distance, accelerations and decelerations).
As practical implications, we may hypothesize that smaller periods of exertion with a greater
number of sets (bouts) can be recommended to ensure a more constant high level of physical demand
and to contribute to an optimization of the high-energy systems that support highly demanding
actions. Possibly, longer bouts should be used in situations in which coaches want to develop aerobic
capacity while players experience acute fatigue eﬀects and consequent decrements in the external load.
Moreover, shorter sets enhance a meaningful greater stimulus in terms of distance covered, running
distance and total number of accelerations and decelerations. However, for a better adjustment of the
training regimen with the reality of the match, it will possibly be interesting in the future to compare
the regular periods of high-intensity eﬀort in the match and adjust such periods in SSGs, thus making
more real the period of high-exertion and the work-to-rest ratios.
5. Conclusions
Between-SSG training regimens revealed that shorter sets (6 × 3’) almost certainly largely increased
total and running distances and very likely moderately and largely increased total accelerations and
decelerations, respectively, in comparison to longer sets (3 × 6’) while likely small increases in RPE
were found in longer sets. The within-regimen analyses revealed that longer sets contributed to
increases in RPE across sets and to large and progressive decreases in total distance and player load
across sets. Additionally, moderate decreases in running distance and total decelerations were found
progressively across shorter sets, while these variables were more stable between longer sets. The
overall conclusions should be faced carefully, considering that the recovery periods were also longer
after the longer periods of exertion.
The results may suggest that shorter sets can be beneﬁcial to maintain external load demands
without resulting in large increases in the perceived eﬀort or heart rate responses, while ensuring a
greater stimulus in total distance, running distance and number of accelerations and decelerations.
However, in terms of acceleration and deceleration proﬁles, it may also be appropriate to choose longer
sets as these contribute to a smaller decrease across sets (decrements are not so meaningful between
sets as in the shorter intervals).
Author Contributions: F.M.C. conceived the study. F.M.C., P.T.N., T.R. and B.K. designed the study. F.M.C.
collected data. F.M.C. analyzed and interpreted the data and drafted the manuscript. F.M.C., P.T.N., T.R. and B.K.
revised the manuscript and approved the ﬁnal version.
Funding: This research received no external funding.
Acknowledgments: The authors would like to thank to Diogo Peixoto, Mónica Gomes, Leandro Silva and Miguel
Moreira for the help in data collection and to JOHAN Sports for providing the GPS units.
Int. J. Environ. Res. Public Health 2019, 16, 2923
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Conﬂicts of Interest: The authors declare no conﬂict of interest.
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(CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Variations of Internal and External Load Variables between Intermittent Small-Sided Soccer Game Training Regimens.
Clemente, Filipe Manuel,Nikolaidis, Pantelis Theodoros,Rosemann, Thomas,Knechtle, Beat