Activity Profile, Heart Rate, Technical Involvement, and Perceived Intensity and Fun in U13 Male and Female Team Handball Players: Effect of Game Format

The aim of the study was to compare the activity pattern, heart rate (HR), technical involvement, and subjective perceptions in U13 boys and girls playing team handball in five game formats. Activity pattern, heart rate (HR), technical involvement, perceived fun, and exertion were recorded from four girls teams (n = 24) and four boys teams (n = 24) played during a 1-day tournament consisting of five different game formats of 15-min duration: Medium court size, 4v4 (M4v4), 5v5 (M5v5), and 6v6 (M6v6), and large court size, 5v5 (L5v5) and 6v6 (L6v6). Girls covered more total distance (TD) and high-speed running (HSR, 13–17.9 km·h−1) on the large court compared to the medium court (p < 0.05; ES = 2.1–3.1 and 1.2–2.5, respectively). Boys covered more distance as HSR and sprinting on the large court compared to the medium court, but only more TD on the large court compared to the medium court with the same number of players, (p < 0.05; ES = 1.0–1.8, 1.0–1.8, and 1.1–1.8, respectively). Team handball for U13 boys and girls is a high-intensity activity irrespective of court size. Increasing the court size with a fixed number of players increased the total distance and HSR, whereas manipulating the number of players on a fixed court size appears to influence technical involvement.


Introduction
Team handball is a physically demanding, high-intensity team sport with a high number of anaerobic actions, such as sprinting, jumping, shooting, and tackling. These actions are repeated multiple times throughout the game interspersed by low to moderate intense activities, adding a considerable aerobic component to the game. This activity pattern results in an average heart rate above 80% of the maximal heart rate [1,2].
Adult team handball is usually played indoor on a 40 m × 20 m court with two teams of seven players, including a goalkeeper. In Denmark, youth team handball is generally played on smaller courts up to the age of 10, after which the game is played on a full court. One previous study in adults investigated the matter of court dimensions in team handball, which indicated that changing the court dimensions affected perceived exertion and activity pattern and HR on the players, but no studies of this type were found in children or adolescents [3]. To our knowledge, only one study has been conducted in youth handball, with the purpose of analysing the activity profile of elite adolescent team handball players during matches [1]. Studies from other team sports, especially football, show that changes in the pitch/court size and number of players can affect the physical and technical demands of the game and player involvement [4,5], while others only found impacts on technical aspects [6]. The use of small-sided games (SSG) is extensively investigated in other sports and the results reveal that the training type has large beneficial effects on VO 2 max, agility, and repeated sprint ability and moderate beneficial effect on 10-and 20-m sprint performance, jump height, and intermittent endurance [7].
For several reasons, it would be of interest to identify the game format associated with the greatest physical load, most fun, and the most technical efforts. For coaches, knowing which format produces the most technical efforts and/or greatest physical load would allow them to make training more specific. In terms of public health, recreational team handball is an important physical activity for many children and adolescents, and small-sided high-intensity intermittent games have been shown to have a significant effect on bone mineralisation and fitness [8,9]. Furthermore, research has shown that children cite "fun" as the most important factor for participating in organised sport, which highlights the importance of this factor for keeping children interested in being active [10] and might help team handball associations to maintain members for a longer period.
Based on previous findings in a study of the game format in U13 football [4], we hypothesized that a larger court will increase the total distance and that fewer players on the court will increase the involvement of the players in terms of more shots and duels per player.
The primary aim of the present study was to describe and compare the activity profile, HR, technical involvement, and perceived fun and exertion in U13 boys and girls in five different game formats. The secondary aim was to compare the outcomes between genders in the different game formats.

Experimental Design
Eight U13 teams played a 1-day tournament in which each team played five different game formats of a 15-min duration. The games were played on a medium-sized court (30 m × 20 m, M) and a large-sized court (20 × 40, L) with 4 to 6 players per team as follows: M4v4, M5v5, M6v6, L5v5, and L6v6. The games were played indoors in a random order with official rules and goal sizes (2 m × 3 m). Activity pattern, HR, technical involvement, and perceptual responses were recorded.
Only those outfield players who played a full match were included in the data analysis. Nonetheless, goalkeepers were allowed to assist their outfield team-mates during the offensive phase of L6v6 games.

Participants
A total of four U13 boys (n = 24) and four U13 girls (n = 24) Danish teams participated in the study.

Activity Pattern
The activity pattern was recorded using a wearable device incorporating a 200-Hz accelerometer and gyroscope (Polar Team Pro system, Polar, Kempele, Finland), which was placed on the lower sternum using an elastic band.

HR Monitoring
HR was recorded with a Polar Team Pro (POLAR, Polar Electro Oy, Kempele, Finland) at 1-s intervals during each game. The HR data were expressed as mean and peak HR attained for each game format. In addition, the HR data were distributed into the following intensity zones: <120, 120-160, 160-180, 180-200, and >200 bpm [4].
Activity profile and HR data were stored in the device and downloaded using the manufacturer's software (POLAR, Software version 1.3.1, POLAR, Polar Electro Oy, Kempele, Finland).

Rating of Perceived Exertion and Fun
Immediately after the end of each match, the players' perceived exertion and perceived fun during the game were rated using two visual analog scales (VAS) [13]. For physical exertion, the players placed a mark on a 17.4-cm line ranging from 'maximally demanding' to 'not demanding at all', while for perceived fun, a similar line was used, ranging from 'maximal fun' to 'not fun at all'. The result was obtained by measuring with a ruler the length (cm) from 0 to the mark made by the player.

Technical Variables
Shots on goal, number of goals scored, and number of duels were counted during the game by officials from the Danish handball federation. Each official followed one or two players per game. Afterwards, the percentage of successful shots was calculated. These technical variables were chosen since they were considered as the most important by the authors. Number of shots indicated the possibilities to create chances. Number of goals indicates how difficult it was to score (scoring changes might be bigger with a certain number of players on a certain court size). Duels were counted since they are a central and physically demanding part of the game.

Statistical Analyses
Considering the fact that the players differed with regard to the number of game formats in which they participated, a linear mixed model with unstructured covariance was used for the analysis of differences between game formats and between gender [14]. The game format was set as the fixed effects and individual subjects and team were set as random effects. Physical, physiological, and perceptual variables were dependent variables. If a significant effect was found, multiple comparisons between game formats were analysed using a Bonferroni correction. Differences between game formats and genders were interpreted using effect sizes (ES) according to Hopkins and Marshall [15] as: Trivial (ES < 0. . When 90% confidence intervals (CI) overlapped positive and negative values, the effect was deemed to be unclear. Otherwise, the effect was deemed to be the observed magnitude [16]. Significance was set at p ≤ 0.05. Data analysis was performed using Statistical Package for Social Science statistical software (version 23, IBM SPSS Statistics, Chicago, IL, USA).

Heart Rate
The girls had a significantly greater HR mean in L5v5 compared to M5v5 (p < 0.05; E = 1.2 [0.6;1.8]). No other differences in HR mean and HR peak were found for the girls (Table 1).

Activity Profile
Boys covered largely greater TD than girls in all game formats played on medium-sized courts (p < 0.05; ES = 1.4 to 1.7). In all game formats, boys had a higher peak speed (p < 0.05; ES = 0.8 to 1.2) and a higher number of sprints (p < 0.05; ES = 0.9 to 1.4) than girls ( Figure 3A).

Discussion
The main findings of the present study were that HR values were high, similar to other SSG with several number of sprints, accelerations, and decelerations during team handball games in U13 players irrespective of gender and game format. For girls, HR was even higher when playing L5v5 compared to M5v5. Both genders covered a greater TD when playing on the large-sized court compared to the medium-sized court with same number of players. The boys had a greater number of sprints when playing on the large-sized court than when playing on the medium-sized court with the same number of players. In general, differences in activity patterns were only seen when comparing the two court sizes, but not when the number of players was altered on the same-sized court.
The physiological response to exercise (mean HR) was high with HRs from 167 to 184 bpm in all game formats for both genders. These values are very similar to previous studies in adolescent team handball players [1] and U13 football players in small-sided games [4], and a little higher compared to school children playing small-sided games [9].
High HR is important for the health profile of children as well as adults, since aerobic highintensity training has been shown to be more effective than continuous aerobic training in respect to improving cardiorespiratory fitness [17,18], which is associated with lower future body mass index body fat percentage, and metabolic syndrome [19]. In adults, two studies have shown beneficial health effects of team handball for inactive men and women [20,21], but no studies have investigated the health effects of recreational team handball in children or adolescents. Other types of small-sided ball games, including unihockey, football, and basketball, studied in a school setting in 8 to 10-yearold children, improved performance in the Yo-Yo Intermittent Recovery level 1 for children, bone mineral density, and structural and functional cardiac adaptations [8,9,22], so it can be expected that team handball could result in similar effects. Boys covered a moderately greater distance by jogging compared to girls in M5v5, M6v6, and L5v5 (p < 0.05; ES = 0.6 to 0.8). Boys covered a moderately greater distance by MSR compared to girls in M4v4, M5v5, M6v6, and L6v6 (p < 0.05; ES = 0.6 to 1.2). Boys covered a moderately to largely greater distance by HSR compared to girls in M4v4, M5v5, and M6v6 (p < 0.05; ES = 0.8 to 1.7), but girls covered a moderately greater distance by HSR than boys in L6v6 (p < 0.05; ES = 0.6 [0.1;1.1]). Boys also covered a moderately to largely greater sprinting distance compared to girls in M4v4, M5v5, M6v6, and L6v6 (p < 0.05; ES = 0.7 to 1.3) ( Figure 3B).

Discussion
The main findings of the present study were that HR values were high, similar to other SSG with several number of sprints, accelerations, and decelerations during team handball games in U13 players irrespective of gender and game format. For girls, HR was even higher when playing L5v5 compared to M5v5. Both genders covered a greater TD when playing on the large-sized court compared to the medium-sized court with same number of players. The boys had a greater number of sprints when playing on the large-sized court than when playing on the medium-sized court with the same number of players. In general, differences in activity patterns were only seen when comparing the two court sizes, but not when the number of players was altered on the same-sized court.
The physiological response to exercise (mean HR) was high with HRs from 167 to 184 bpm in all game formats for both genders. These values are very similar to previous studies in adolescent team handball players [1] and U13 football players in small-sided games [4], and a little higher compared to school children playing small-sided games [9].
High HR is important for the health profile of children as well as adults, since aerobic high-intensity training has been shown to be more effective than continuous aerobic training in respect to improving cardiorespiratory fitness [17,18], which is associated with lower future body mass index body fat percentage, and metabolic syndrome [19]. In adults, two studies have shown beneficial health effects of team handball for inactive men and women [20,21], but no studies have investigated the health effects of recreational team handball in children or adolescents. Other types of small-sided ball games, including unihockey, football, and basketball, studied in a school setting in 8 to 10-year-old children, improved performance in the Yo-Yo Intermittent Recovery level 1 for children, bone mineral density, and structural and functional cardiac adaptations [8,9,22], so it can be expected that team handball could result in similar effects.
It might be claimed that the mean HR in the present team handball games are only a moderate-intensity activity, but team handball is an intermittent game with many actions of high intensity, as indicated by the HR peak values between 192 and 202 bpm. Furthermore, team handball is a game with many changes of direction and in the present study, a little less than 400 total accelerations and decelerations were counted during each 15-min. game. To our knowledge, this is the first study to count accelerations during team handball.
Most of the TD was covered by jogging for both genders irrespective of the court size, but when games were played on the large-sized court, the boys' running intensity was higher and significantly more distance was covered by MSR, HSR, and sprinting. Thus, a change in court size, but not the number of players, had a large effect on the boys' V peak during games (ES = 1.3 to 2.3). This was also observed by Condivo et al. (2014) in adult men playing team handball, where the same number of players on a larger court covered a greater distance in higher speed zones compared to a smaller court.
Regarding gender-related differences, boys covered more distance by sprinting compared to girls (ES = 0.7 to 1.3) in all game formats except L5v5 and had higher V peak and a higher number of sprints in all game formats. This underlines the fact that boys are generally faster than girls [23,24]. In support of this observation, a study by Michalsik and Aagaard (2014) comparing adult elite women and male team handball players during matches found that men produced more high-speed running than women [25]. Furthermore, the study by Michalsik and Aagaard (2014) observed that female players covered greater TD than male players during a team handball game. Interestingly, the opposite was found in this study, but only on the medium-sized court, with boys covering greater TD than girls. No differences were found between genders on the large-sized court. The difference in TD between genders in this study may be explained by differences in the game pattern or simply the boys' ability to run faster, since a greater distance was covered by MSR, HSR, and sprinting in the boys' game. Moreover, the higher number of sprints in the same game formats might explain the greater number of accelerations and decelerations for boys, especially for accelerations over 2.3 m·s −2 on a medium-sized court and decelerations under −2.3 m·s −2 on a medium-sized court and in L5v5.
Girls had more accelerations above 2.3 m·s −2 when playing on the large-sized court compared to the medium-sized court with the same number of players. This might be an effect of more space per player on the larger court, since the findings are similar to results from a study by Randers et al. (2018), who observed increased time in the two highest player load zones when the participants played 3v3 basketball on a full court compared to a half court [26].
In respect of the technical aspects of the game, girls had more shots and scored more goals per player when playing M4v4 compared to all other game formats. Boys had more shots per player when playing M4v4 compared to M6v6 and L6v6, but more goals were scored only in M4v4 compared to L6v6. This observation may simply be explained by the fewer number of players and greater space per player, which gave more opportunities to shoot. It is in line with studies of small-sided football games with different numbers of players, which showed a higher number of actions and more ball contact per player when the number of players decreased [4,6].
Boys reported it was more physically demanding playing L5v5 compared to M5v5 and M6v6, whereas girls found it more demanding playing both large-court formats compared to M6v6. For both genders, the observed differences in perceptual responses might be due to the larger court resulting in more TD covered and more time spent in higher speed zones, even though this did not result in increased HR. A positive relationship exists in the literature between total distance and rate of perceived exhaustion (RPE), and other studies have reported similar observations, with increased court size reported to elicit a greater response in RPE in team handball and football without any changes in HR [3,5,27]. In addition, boys reported it was more demanding playing M5v5 and L6v6 compared to girls. The difference might be due to a higher number of sprints in boys' games, but this is not supported by differences in HR. In respect of RPE, it is important to stress that not only is RPE mediated by physiological factors, but psychological factors are also important, which may explain the difference in RPE in the present study [28].
A limitation of this study is that the maximal HR of the participants was unknown. A measure of maximal HR would have made it possible to calculate a precise estimate of the individual aerobic load during the games. Furthermore, precise individual measures of anthropometrics, state of matureness, and fitness components, such as maximal sprinting speed, would give a more precise description of the participants and might explain some of the differences between boys and girls, and give the opportunity to adjust the speed zones to gender. Gender differences have been studied in football [29], but have not been studied so far in team handball.
Only a limited number of technical variables have been included in the study due to a limited number of officials. Other technical variables, such as placement of the shots and the shooters' position on the court, would be of interest to investigate if a specific game format would favour shooting from specific positions or if more goals were scored in a specific part of the goal.
Finally, it has not been possible to find any independent scientific validation studies for the equipment used to measure activity patterns. For this reason, the results of these measurements must be used with caution until the equipment is validated.

Conclusions
HR was high with several sprints, accelerations, and decelerations in U13 team handball irrespective of gender and game format. Greater TD was covered when the court size was increased, and boys performed more sprints on the large-sized court compared to the medium-sized court with