Comparison of the Acute Effects of Carbohydrate Mouth Rinse and Coach Encouragement on Kinematic Profiles During Small-Sided Games in Young Male Soccer Players

Carbohydrate mouth rinsing (CHOmr), a nutritional intervention for delaying fatigue and meeting the energy demands of soccer, and the motivational strategy of coach encouragement (CE) are widely recognized as effective approaches for enhancing athletic performance in soccer. Objectives: This study aimed to compare the effects of CHOmr + CE, CHOmr, and CE on heart rate (HR) and kinematic profiles during four-a-side small-sided soccer games (SSGs). Methods: Twenty-four young soccer players (age: 17.2 ± 0.8 years) played six bouts of four-a-side SSGs with CHOmr + CE, CHOmr, or CE at 3-day intervals in a randomized, single-blinded, placebo-controlled, or crossover study design. The HR and kinematic responses were continuously recorded during all games. Results: There were no statistically significant differences between the groups in peak heart rate (HRpeak) (p ≥ 0.05, F = 0.326, p = 0.723, η2 = 0.014) and mean heart rate (HRmean) (p ≥ 0.05, F = 0.845, p = 0.436, η2 = 0.035). No significant differences were found for distances in Zone 1 (p ≥ 0.05, F = 1.21, p = 0.306, η2 = 0.050), Zone 4 (p ≥ 0.05, F = 0.310, p = 0.735, η2 = 0.013), Zone 5 (p ≥ 0.05, F = 1.02, p = 0.368, η2 = 0.042), or Zone 6 (p ≥ 0.05, F = 0.161, p = 0.211, η2 = 0.055), nor acceleration (p ≥ 0.05, F = 0.208, p = 0.137, η2 = 0.083) and deceleration (p ≥ 0.05, F = 0.790, p = 0.460, η2 = 0.033). Similarly, although no significant differences were observed in the distance in Zone 3 (p ≥ 0.05, F = 3.12, p = 0.054, η2 = 0.119) or repeated sprint distance (p ≥ 0.05, F = 2.96, p = 0.062, η2 = 0.114), the CHOmr +CE group exhibited higher average values for these variables. However, a statistically significant difference was observed in the distance covered in Zone 2 (p ≤ 0.05, F = 3.89, p = 0.028, η2 = 0.145), with the CHOmr +CE group performing better, as confirmed by the post-hoc analyses. Conclusions: Although our findings indicate that CE alone may influence kinematic profiles during SSGs, similar to CHOmr or its combination with CE, further research should explore the underlying mechanisms and potential contextual factors influencing these outcomes. Therefore, we suggest that coaches prefer CE because it is easy to implement.