HEART RATE,TIME-MOTION, AND BODY IMPACTS WHEN CHANGING THE NUMBER OF TEAMMATES AND OPPONENTS IN SOCCER SMALL-SIDED GAMES LORENA TORRES-RONDA, 1 BRUNO GONC ¸ ALVES, 2 RUI MARCELINO, 2 CARLOTA TORRENTS, 1 EMILI VICENTE, 1 AND JAIME SAMPAIO 2,3 1 National Institute of Physical Education of Catalonia (INEFC), University of Lleida, Lleida, Spain; 2 Research Center in Sports Sciences, Health Sciences and Human Development (CIDESD), Vila Real, Portugal; and 3 CreativeLab Research Community, Tra´s-Os-Montes e Alto Douro University, Vila Real, Portugal ABSTRACT Torres-Ronda, L, Gonc ¸ alves, B, Marcelino, R, Torrents, C, Vicente, E, and Sampaio, J. Heart rate, time-motion, and body impacts when changing the number of teammates and opponents in soc- cer small-sided games. J Strength Cond Res 29(10): 2723– 2730, 2015—The purpose of this study was to determine the internal (heart rate) and external load (body load, distance covered, and exertion index) during different types of unbal- anced soccer small-sided games (SSGs) in professional (PRO) and amateur (AMA) players. In 2 separated sessions (PRO and AMA), participants played 3 SSG formats (4vs3, 4vs5, and 4v7). Data were analyzed from the fixed team’s perspective (4vsX) according to the number of opponents (3, 5 and 7) and from the variable team (3 + Xvs4) according to the teammates (without teammates, 2 and 4 teammates). The time-motion and body impact data were collected using a nondifferential global positioning system with integrated heart rate measurement. Differences in internal and external workload between the game formats were compared using Cohen’s d unb effect sizes with 95% confidence intervals. Re- sults reveal that the higher the number of players involved in the task, the lower the internal and external workload. The analysis also showed different teammates and opposition- related trends that need to be considered when planning and monitoring training performance. Playing in low-inferiority (4vs3 and 4vs5) had higher physiologic impact to players than the other higher unbalanced situations. This evidence was similar to both PRO and AMA players; however, the PRO presented higher physical and lower physiological responses across games. Our results suggest that coaches should con- sider the usage of unbalanced SSG formats to simultaneously facilitate the emergence of defensive and offensive proficient scenarios also representing opportunities to increase the practice workload. KEY WORDS workload, game format INTRODUCTION O ptimal performance in soccer emerges from the interaction between players’ constraints (physi- ological, technical, or tactical capacities), the environment (pitch conditions), and the tasks (game rules), mainly throughout a self-organization process (10,22). In such unstable and complex environments, perfor- mance is highly unpredictable and requires that players adapt their behavior to a wide range of different playing scenarios. In fact, the variation in any constraint will affect the whole system and will create a different playing scenario that needs to be described to better understand the game. For example, modifying the pitch size or the number of players will change several space-time informational sources, affecting players’ decision-making and physiological responses (3). The available research that describes constraints manipu- lation during small-sided games (SSGs) has increased signif- icantly in the last years (3,17). These training situations develop simultaneously technical and tactical skills under spe- cific physical loads (17) and maintain players’ higher motiva- tion in unpredictable environments, when compared with nonspecific training situations. Mainly, results describe the effects of manipulating selected game rules, the pitch size, the number of players, the presence of goalkeepers, the pres- ence and the size of the goals, the duration of the exercise, coach encouragement, and the balance of opponents (3). The most common responses analyzed are physiological (heart rate, blood lactate), physical (distances, speeds, time), percep- tual, and technical (3,14,17,25). In general, results suggest that the fewer players involved, the greater physiological percep- tual responses and number of technical actions (6,12,23). However, some results suggested that when comparing with Address correspondence to Dr. Lorena Torres-Ronda, lorenatorres07@ yahoo.es. 29(10)/2723–2730 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association VOLUME 29 | NUMBER 10 | OCTOBER 2015 | 2723 Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.