What changes when young footballers play the same small-sided game in heat? Their heart rates and perceived effort rise, while the number of completed passes falls. Football player performance is influenced by various factors that interact to shape performance on the field.

Match dynamics, situational variables, and environmental conditions all help determine players’ responses during gameplay. Temperature is a significant environmental determinant, and extreme conditions like cold and hot environments have noticeable effects on performance during matches.

Evidence regarding heat temperature’s impact on football matches is well-established, but original research in training contexts lacks robustness. That gap matters for small-sided games, where environmental conditions can interact with task constraints to influence players’ responses.

Small-sided games are frequently employed by soccer coaches as a multifaceted training drill with various objectives. They provide a high-intensity workout while facilitating frequent practice of specific technical skills and specialized tactical behaviors.

Training drills may be influenced by environmental temperatures, particularly hot conditions, which could impair drill performance and ultimately affect training adaptations. The study compares hot and moderate environmental temperatures in male soccer players, focusing on heart rate responses, perceived effort, and technical performance.

The hypothesis was that heart rate responses and perceived exertion would be significantly higher during hot conditions, while lost balls would also increase in hot conditions. The study used a repeated measures design, so the same players engaged in the same three-versus-three small-sided game format under two conditions: outdoor wet bulb globe temperature below 21 degrees Celsius and above 21 degrees Celsius.

Under each condition, players took part in two training sessions in the same week, separated by two days, and completed two repetitions of the small-sided game format. Figure one outlines the repeated-measures schedule: the same players completed three-versus-three small-sided games under the below twenty-one-degree condition during the first week, then repeated the protocol under the above twenty-nine-degree condition in the fourth week.

The two conditions were separated by two weeks, helping the authors compare temperature contexts within the same group rather than relying on different players. Table one summarizes the participant profile across the Under-16 and Under-19 groups, with thirty players in each group and sixty overall.

The table reports age, body mass, height, and years of soccer experience as means plus or minus variability. The Under-16 players averaged sixteen point three years of age and five point one years of experience, while the Under-19 players averaged seventeen point six years and six point eight years, respectively.

This establishes the demographic context for interpreting the study’s soccer and physiological measurements. The three-versus-three format used a 26 by 22 meter field, with 95.3 square meters per player. The objective was to score in a small target measuring 2 by 1 meter, with no offside rule enforced.

Teams comprised one defender, one midfielder, and one attacker whenever possible. Team composition stayed unchanged, and players competed against the same opponents to ensure reproducibility of conditions. The game was used twice, each time for three minutes with a three-minute rest period, following a standardized warm-up protocol.

The warm-up included eight minutes of running at 60 to 65 percent of maximal heart rate, followed by six minutes of dynamic stretching, three minutes of short accelerations, decelerations, and reactive jumps, and a three-minute rest period. Throughout all the three-versus-three games, players were continuously monitored using individual heart rate sensors that recorded data at one-second intervals.

The sensors were H10 Bluetooth monitors from Polar Electro, and the Polar H10 demonstrates strong agreement with other heart rate systems, supporting accurate heart rate measurement. Mean heart rate was calculated over the duration of the games and used for further data analysis.

Figure two compares mean heart rate and perceived exertion below twenty-one degrees Celsius and above twenty-nine degrees Celsius, for all players and separately for the under-sixteen and under-nineteen groups. The paired points, boxplots, and distributions show individual responses and group summaries, with an asterisk indicating significant within-group differences at p less than zero point zero zero one.

This matters because the authors identify heat-related increases in both cardiovascular response and perceived effort during small-sided games. Overall, temperatures above 29 degrees Celsius produced significantly higher mean heart rate and rate of perceived exertion, with both results reported at a p-value below 0.001.

Significantly more passes were completed below 21 degrees Celsius, also with a p-value below 0.001. Table 2 shows the descriptive statistics for all players and the age groups. Table two compares small-sided-game outcomes below twenty-one degrees Celsius and above twenty-nine degrees, for under-sixteen, under-nineteen, and overall groups.

Across groups, the table reports higher mean heart rates and CR10 Borg ratings in the hotter condition, with p-values below zero point zero zero one and large d-values. Pass counts were also significantly different, while lost-ball counts were not, with p-values from zero point one zero eight to zero point three eight six.

Figure three compares completed passes and lost balls in cooler conditions, below twenty-one degrees Celsius, versus hot conditions, above twenty-nine degrees Celsius. Panels show the overall participants and separate under-sixteen and under-nineteen groups, using paired observations, boxplots, and distribution shapes.

The asterisks mark significant within-group differences for completed passes, highlighting that heat conditions were associated with measurable changes in technical performance during the small-sided games. During small-sided games in hot conditions, significant decreases in completed passes were observed, along with an increase in unsuccessful passes.

The effects of heat conditions on technical performance are conflicting: some studies show no meaningful impact, while others demonstrate increases in instances of lost balls. One limitation is that the study focused exclusively on male youth categories, which may limit generalizability to elite adult athletes or females.

The study examined only ambient temperature at the start of the match and did not consider atmospheric pressure, wind, humidity, or precipitation. Those factors, along with possible temperature fluctuations during the game, might also impact physical performance, particularly if the kick-off time varies.

Heat conditions above 29 degrees Celsius, compared with moderate temperatures below 21 degrees Celsius, significantly intensified heart rate responses and perceived exertion. The number of passes was significantly affected by heat, although the number of lost balls did not show a significant difference between temperature conditions.

Coaches should consider mitigating heat conditions during small-sided training sessions by implementing pre-cooling techniques and ensuring adequate hydration levels among players. In this study, temperatures above 29 degrees Celsius intensified heart-rate and perceived-effort responses and reduced completed passes, while lost balls did not differ significantly.

Heat mitigation matters during small-sided training.