A hot football session can make young players’ hearts race and effort feel harder, yet the clearest sign may be quieter: they complete fewer passes. The surprising part is what heat does not change. Football player performance is influenced by factors that interact to shape what happens on the field.

Match dynamics, situations, and environmental conditions all affect players’ responses during gameplay. Temperature is a significant environmental factor: cold and hot environments can noticeably affect performance during matches. The same concern applies to training drills.

Hot conditions could impair drill performance and ultimately affect training adaptations. The study compares hot and moderate environmental temperatures by looking at heart rate responses, perceived effort, and technical performance during small-sided games.

The comparison used temperatures below 21 degrees Celsius and above 29 degrees Celsius. Players took part in the same small-sided game format under both temperature conditions. The games were judged through heart rate, how hard the players felt they were working, successful passes, and lost balls.

The small-sided game put three players against three on a smaller field, with the aim of scoring in a small target. No offside rule was used, while the other rules stayed consistent with the official game. Each team included a defender, a midfielder, and an attacker whenever possible, and the teams and opponents stayed unchanged throughout the sessions.

In the heat, players’ hearts worked harder and they felt the effort more strongly, and this same pattern appeared across both age groups. The differences were statistically strong, with the chance of appearing randomly below one in a thousand. In hotter training sessions, players completed significantly fewer passes and lost more balls, a pattern visible across the overall group and both age groups.

The result suggests that heat affects not only how hard the session feels, but also the accuracy of play. These findings cannot automatically be applied to everyone. The study focused exclusively on male youth players, so the results may not extend to elite adults or females.

The study examined the air temperature at the start of the match, without considering wind, humidity, precipitation, air pressure, or temperature changes during the game. Compared with moderate temperatures, heat above 29 degrees Celsius significantly intensified heart rate responses and the effort players reported feeling.

Heat significantly affected the number of passes, although the number of lost balls did not differ significantly. Coaches should consider reducing heat stress during training with cooling before play and adequate hydration. For young male players in small-sided games, heat raises physical strain and perceived effort while reducing completed passes, without significantly changing lost balls.

Training in heat may therefore need cooling and hydration measures.